JP2003293019A - Method for producing reduced iron using wet dust of blast furnace and method for producing crude zinc oxide - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a reduced iron by which the collapse and the powdering of a pellet in a heating furnace is prevented and the product reduced iron having high dezincifying rate and high metallizing rate can be produced at a high yield, when the pellet containing wet dust of a blast furnace is heated and reduced in the heating furnace to obtain the reduced iron. <P>SOLUTION: The wet dust of the blast furnace containing psudo-grain having >1 mm grain diameter is crushed with a crusher 1 so that the mass ratio of the psudo-grain having >1 mm grain diameter in the following mixed raw material becomes ≤50%. Powdery raw material containing at least iron oxide is added to the wet dust of the blast furnace after crushing, and mixed with a mixer 2 and this mixed raw material is pelletized with a pelletizer 3. The pellet is dried until becoming #1.0 mass% moisture content with a dryer 4, and this dried pellet is heated and reduced in the heating furnace to obtain the reduced iron. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for producing reduced iron using blast furnace dust and a method for producing crude zinc oxide (a method for reducing other iron mill dust using blast furnace dust). is there.

[0002]

2. Description of the Related Art Blast furnace dust includes dry coarse dust particles, which are relatively coarse particles, and fine wet dust particles, which are wet particles. Since the dry dust has a relatively low zinc content compared to the wet dust, it can be reused as a raw material for sinter, but since the wet dust has a very high zinc concentration, it can be reused as a blast furnace raw material. In this case, dezincification treatment is essential.

Therefore, in recent years, various methods for dezincing blast furnace wet dust have been studied. Among them, as a process that can dezinc the blast furnace wet dust and reduce it effectively to reuse it as an iron source, the mixed raw material containing the blast furnace wet dust is agglomerated and heated and reduced in a rotary hearth furnace. The method of obtaining reduced iron (rotary hearth furnace method) has high productivity,
It has come to be put into practical use as the most effective process because of the low equipment cost (for example, Japanese Patent Laid-Open No. 11-241125).

The outline of the dezincification / reduction treatment of blast furnace wet dust by the rotary hearth furnace method is as follows (see FIG. 3).
The blast furnace wet dust A contains a large amount of water because it is a fine dust in the blast furnace top exhaust gas collected by a wet dust collector. Therefore, after dehydration for the purpose of facilitating the transportation, it is dried by a rotary dryer or a fluidized bed dryer. However, if it is too dry, dust is generated during the transportation.
The water content is adjusted to about 0 to 30% by mass.

Further, the blast furnace wet dust A contains carbon (C) in a high concentration in addition to iron oxide and zinc oxide (usually 2
(0 to 40% by mass), when the blast furnace wet dust A is agglomerated alone and heated and reduced, iron oxide and zinc oxide are reduced, and a large amount of excess C remains. Therefore, powdered raw material B such as iron ore or other iron mill dust is added to the blast furnace wet dust A as an iron oxide source, and water and a binder are further added if necessary, and this is mixed by a mixer 102 and mixed. Use as raw material (mixing process). This mixed raw material is granulated into raw pellets by the granulator 103 (agglomeration step). The raw pellets are dried by the drier 104 until the water content is not more than the predetermined amount, to obtain dried pellets (drying step). Dry pellet charging device 105
Thus, about 1 to 2 layers are placed on the hearth of the rotary hearth furnace 106 (charging step). The pellets are radiantly heated by a burner 107 provided in the furnace while passing through the furnace as the hearth rotates. By this radiant heating, moisture remaining in the pellets is completely removed, and the pellets are heated to about 1200 ° C or higher. Then, iron oxide or zinc oxide in the pellets is reduced by C in the blast furnace wet dust. The iron oxide in the pellets is reduced to metallic iron, while the zinc oxide is reduced to metallic zinc vapor, which is volatilized and removed in the exhaust gas of the furnace (reduction step). As a result, the pellets discharged from the rotary hearth furnace 106 become dezinced reduced iron and a high-quality iron source is obtained. Further, the metal zinc vapor removed in the exhaust gas is oxidized by the oxidizing components (CO ₂ , H ₂ O) in the exhaust gas and returns to solid-phase zinc oxide to become fine particles, so the dust collector 108
It can be used as a high-quality zinc material (zinc recovery step).

[0006] In the above, the raw pellets are put into the rotary hearth furnace 1
The purpose of drying before charging to 06 is to prevent so-called bursting, in which the pellet explodes due to rapid evaporation of water when the pellet is heated in the furnace.

[0007] The applicant of the present invention discloses in Japanese Patent Laid-Open No. 11-193423 that, when iron ore is used as a raw material for iron oxide and pellets made of a mixture obtained by adding a carbonaceous material such as coal to the iron ore are used, In order to prevent sting and ensure the handling strength (falling strength, crushing strength, etc.) of the dried pellets in the charging step, it is necessary to dry the dried pellets until the water content is 1% by mass or less. I disclosed that.

However, when blast furnace wet dust is used, even if the moisture in the dried pellets is dried to 1% by mass or less and then charged into a rotary hearth furnace, the pellets are significantly collapsed or pulverized in the furnace. In addition to the difficulty of handling the product reduced iron due to the generation of a large amount of powder, in addition to problems such as a decrease in the metallization rate and dezincification rate of the product reduced iron and a decrease in the yield, it was recovered. It has been found that a large amount of iron oxide is mixed into the crude zinc oxide, which causes a problem of degrading the quality as a zinc raw material (prior art 1).

[0009] Here, in Japanese Patent Laid-Open No. 2001-303115, a mixture containing undried blast furnace wet dust and the like is squeezed and dehydrated and then extrusion molded, and the molded body is placed in a rotary hearth furnace without drying. A method for producing reduced iron by charging, drying, heating, and reducing in a furnace is disclosed. In this method, the degree of dehydration and the powder filling rate of the molded body by extrusion molding are controlled to prevent the molded body from bursting in the furnace. However, as will be described later, since the blast furnace wet dust causes reduction expansion, it is not possible to sufficiently prevent the collapse or pulverization of the compact by merely preventing the explosion at the time of water evaporation. Furthermore, in this method, since the compact is dried in the rotary hearth furnace and then reduced, it is necessary to prolong the residence time in the furnace and to increase the hearth area. (Prior art 2).

[0010]

DISCLOSURE OF THE INVENTION The present invention has been made to solve the above-mentioned problems. Even when wet blast furnace dust is used, pellets (agglomerates) are not collapsed or pulverized in the furnace. It is an object of the present invention to provide a method for producing reduced iron that is capable of producing a product reduced iron having a high metallization rate with a high yield, and a method for producing crude zinc oxide that can obtain a high-quality zinc raw material.

[0011]

Means for Solving the Problems The present inventors have
In order to investigate the cause of pellet collapse and pulverization in the case of using blast furnace wet dust, the microstructure after reduction of blast furnace wet dust itself and pellets containing blast furnace wet dust were observed. As a result, it was found that the causes of pellet disintegration and pulverization were as follows.

As described above, the blast furnace wet dust is dried with a certain amount of water remaining, but when the fine powder raw material is dried, it is not completely uniformly dried, and the fine powder raw material contains a large amount of water. There are many parts, and this part is likely to be a pseudo particle due to the granulation action by stirring with a dryer. The pseudo particles formed in this way are very strong because the constituent particles are fine powders, and are not easily crushed by the impact force of the stirring in the mixer 1 in the mixing step.

On the other hand, FIG. 4 is a microscopic observation of the powder contained in the product reduced iron. From this figure, it was found that the metallic iron produced by the reduction grows like whiskers. Therefore, as a result of separately heating and reducing a sample of pellets composed of only blast furnace wet dust in a small heating furnace, and observing the sample after reduction with a microscope, almost the same formation of metallic iron whiskers was observed. Therefore, it has been found that the blast furnace wet dust is reductively expanded by the formation of metallic iron whiskers.

Therefore, when the pellets agglomerated while containing a large number of pseudo particles are heated in the rotary hearth furnace 106, the pseudo particles composed of only blast furnace wet dust as described above remarkably reduce and expand. On the other hand, the surrounding area, where the content ratio of the blast furnace wet dust is small, does not expand as much as the pseudo particles, stress concentration occurs near the pseudo particle surface and cracks occur, and the pellets collapse due to the propagation of these cracks. It is thought to lead to pulverization.

Therefore, the present invention is characterized in that the number of pseudo particles causing the above stress concentration is reduced as much as possible before agglomeration, and the gist thereof is as follows. .

According to the first aspect of the present invention, the blast furnace wet dust containing pseudo particles having a particle size of more than 1 mm is crushed so that the mass ratio of the pseudo particles having a particle size of more than 1 mm in the mixed raw material is 50% or less. A crushing step, a mixing step of mixing the crushed blast furnace wet dust with at least a powdery raw material containing iron oxide to form a mixed raw material, and an agglomeration of the mixed raw material to agglomerate A method for producing reduced iron using blast furnace wet dust, comprising: a liquefaction step and a reduction step of heating and reducing this agglomerate to obtain reduced iron.

According to a second aspect of the present invention, the mass ratio X _Q (unit: mass%) of the pseudo particles having a particle size of more than 1 mm in the mixed raw material and the surplus carbon rate S _C (unit: mass%) are as follows. The method for producing reduced iron using the blast furnace wet dust according to claim 1, which satisfies the expression (1).

[0018] Equation (1) when 0 ≦ S _C ≦ 2, when _{X Q ≦ 50 2 <S C} ≦ 6, here _{X Q ≦ 70-10 · S C,} S C = X C - (12 / 16) · X _O (where X _C is the mass ratio (mass%) of carbon in the agglomerate after drying, and X _O is the oxygen and oxidation of iron oxide in the agglomerate after drying). The ratio (mass%) of the total mass of zinc and oxygen.)

According to the invention of claim 3, the mass ratio X _Q (unit: mass%) of the pseudo particles having a particle size of more than 1 mm in the mixed raw material and the surplus carbon rate S _C (unit: mass%) are as follows. The method for producing reduced iron using the blast furnace wet dust according to claim 1, which satisfies the expression (2).

[0020] Equation (2) when 0 ≦ S _C ≦ 1, when _{X Q ≦ 50 1 <S C} ≦ 6, here _{X Q ≦ 60-10 · S C,} S C = X C - (12 / 16) · X _O (where X _C is the mass ratio (mass%) of carbon in the agglomerate after drying, and X _O is the oxygen and oxidation of iron oxide in the agglomerate after drying). The ratio (mass%) of the total mass of zinc and oxygen.)

[0021] In the invention of claim 4, the water content of the agglomerate is 1.0% by mass between the agglomeration step and the charging step.
4. A drying process, wherein a drying process is performed to dry until:
The method for producing reduced iron using the blast furnace wet dust according to any one of 1.

According to a fifth aspect of the present invention, the blast furnace wet dust is dried to a predetermined water content so that the water content of the mixed raw material is 1.0% by mass or less.
It is a reduced iron manufacturing method using the blast furnace wet dust according to any one of 1 to 3.

According to the invention of claim 6, in addition to each step of the method for producing reduced iron according to any one of claims 1 to 5, zinc recovery for recovering the dezincified zinc component as crude zinc oxide is carried out. A method for producing crude zinc oxide using blast furnace wet dust, which is characterized in that steps are provided.

[0024]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a diagram showing the outline of the equipment configuration for carrying out the method for producing reduced iron (the method for producing crude zinc oxide) using wet dust in a blast furnace of the present invention.

Reference numeral 1 is a crusher, and a known crusher or crusher such as a rod mill, a ball mill or a jaw crusher can be used. The blast furnace 1 crushes the blast furnace wet dust A containing pseudo particles having a particle size of more than 1 mm until the ratio of the pseudo particles having a particle size of more than 1 mm becomes 50% by mass or less in the mixed raw material (crushing step). . To the crushed blast furnace wet dust A, at least a powdery raw material B containing iron oxide (for example, iron ore powder, converter dust, electric furnace dust, mill scale, other steel mill dust such as mill sludge) is added. To do. If necessary, add water. Furthermore, if necessary, coal,
Carbonaceous materials such as coke and petroleum coke, and binders such as starch and bentonite may be added. This is mixed in a known mixer 2 such as a drum mixer to be a mixed raw material (mixing step), and the mixed raw material is granulated (agglomerated) into raw pellets by a known granulator 3 such as a pan type pelletizer and a drum type pelletizer. (Granulation process). Next, the raw pellets are dried with a known dryer 4 such as a Great dryer to a water content of 1% by mass or less to obtain dried pellets. Since the pseudo particles of dense blast furnace wet dust are crushed to some extent in advance and then granulated (agglomerated), the drying time is shortened (drying step). The dried pellets are placed in about 1 to 2 layers on a hearth (not shown) that horizontally rotates in the rotary hearth furnace 6. The pellets are rotated by the rotary hearth furnace 6 as the hearth rotates.
While passing inside, it is radiantly heated by a burner 7 provided above the hearth. By this radiant heating, the moisture remaining in the pellets is completely removed, the pellets are heated to about 1200 ° C. or higher, and the reduction is started. Particle size 1m in pellet
Since the proportion of the pseudo particles exceeding m is limited to the predetermined value or less, even if the blast furnace wet dust forming the pseudo particles is reduced and expanded, the pellets are not disintegrated or pulverized. Therefore, since the reduction reaction proceeds in a state where zinc oxide and iron oxide are in intimate contact with C in the pellet, product reduced iron having a high dezincification rate and metallization rate can be obtained at a high yield (reduction step). . Further, zinc oxide contained in the exhaust gas of the furnace is recovered by a known dust collector 8 such as a bag filter after cooling the exhaust gas, but since the amount of pelletized powder in the furnace is reduced, Impurities such as iron are less mixed in the recovered zinc oxide, high-quality crude zinc oxide is obtained, and the utility value as a zinc raw material is significantly improved (zinc recovery step).

In the crushing step, the mass ratio X _Q (unit: mass%) of the pseudo particles having a particle size of more than 1 mm in the mixed raw material is related to the surplus carbon ratio S _C (unit: mass%). It is preferable to crush the blast furnace wet dust so as to satisfy the following formula (1).

[0028] Equation (1) when 0 ≦ S _C ≦ 2, when _{X Q ≦ 50 2 <S C} ≦ 6, here _{X Q ≦ 70-10 · S C,} S C = X C - (12 / 16) · X _O (where X _C is the mass ratio (mass%) of carbon in the agglomerate after drying, and X _O is the oxygen and oxidation of iron oxide in the agglomerate after drying). The ratio (mass%) of the total mass of zinc and oxygen.)

That is, the larger the surplus carbon ratio S _C , the larger the surplus C amount that exceeds the theoretical C amount necessary to completely reduce zinc oxide and iron oxide to metals. Since the pellets are heated by the burner in the rotary hearth furnace 6, the oxidizing component (CO ₂ , H ₂ O) in the burner combustion gas partially consumes C in the pellets by the solution loss reaction, and Once reduced, the metallic iron is reoxidized. Therefore, in order to obtain a sufficient metallization rate, a considerable amount of surplus C is required. Therefore, the larger the amount of surplus C (that is, the surplus carbon rate S
_The larger the value of _C ), the higher the dezincification rate and the metallization rate are obtained, but on the other hand, when the amount of C in the pellet increases, the sintering of metallic irons is hindered and the powdering of the pellet becomes It is easy to be done. Therefore, pulverization can be more reliably prevented by decreasing the mass ratio X _Q of the pseudo particles having a particle size of more than 1 mm along with the increase of the surplus carbon rate S _C. In the range of 0 ≦ S _C ≦ 2, it is not necessary to decrease the mass ratio X _Q of the pseudo particles having a particle size of more than 1 mm even if the surplus carbon ratio S _C is increased. _C
Then, C hardly remains in the reduced iron due to the above-mentioned solution loss reaction or the like, so that sintering of metallic irons is not hindered. Further, in the range of S _C > 6, the amount of residual C in the reduced iron becomes excessively large and the sintering of metallic irons is significantly hindered, so even if the pseudo particles having a particle size of more than 1 mm are completely eliminated, pulverization is sufficiently performed. Cannot be prevented.

Further, in order to satisfy the following formula (2), it is possible to further limit the mass ratio X _Q of the pseudo particles having a particle size of more than 1 mm from the formula (1) to crush the blast furnace wet dust after the reduction. It is more preferable because it is possible to more surely prevent pulverization of the pellets.

Formula (2) When 0 ≦ S _C ≦ 1, X _Q ≦ 50 1 <S _C ≦ 6, X _Q ≦ 60-10 · S _C

In the above embodiment, only pellets were described as agglomerates, but the present invention is not limited to this, and briquettes, plate-shaped molded products, cylindrical molded products and the like may be used. Therefore, the agglomeration means is not limited to granulation by a pelletizer, and a pressure molding machine or an extrusion molding machine may be used. When briquettes are used, pressure molding can be performed even if the mixed raw material has a small amount of water. Therefore, a blast furnace wet dust that has been dried to a predetermined water content is used to mix water with a water content of 1% by mass or less. It is also possible to prepare a raw material and press-mold it as it is to form a briquette. In this case, the drying process between the agglomeration process and the charging process can be omitted.

[0033]

Example The following experiments were carried out using blast furnace wet dust having the chemical components shown in Table 1 and converter dust collected dust. The moisture content of the blast furnace wet dust was 14% by mass. The blast furnace wet dust was separated by a sieve into particle sizes of 1 mm or less and 1 to 2 mm, respectively. Then, a mixture of blast furnace wet dust having a particle diameter of 1 to 2 mm, blast furnace wet dust having a particle diameter of 1 mm or less, and converter dust collection dust is changed to prepare a mixture, and the mixture is humidified by a ribbon mixer. Various mixed raw materials were prepared by mixing for 2 minutes (while adding water). This mixed raw material was granulated into raw pellets having a diameter of about 14 mm with a pan type pelletizer having a diameter of 1 m. Water content of raw pellets is 13-14
It was mass%. The raw pellets were dried with a small dryer to a water content of 1% by mass or less to obtain dried pellets. Next, the dried pellets were charged into a small heating furnace maintained at 1230 ° C., and held for 20 to 25 minutes to be heated and reduced to reduce iron, and the degree of collapse and pulverization of the pellet due to the reduction was measured. During heating / reduction, a gas of CO ₂ / N ₂ = 20% by volume / 80% by volume was circulated in the small heating furnace, assuming an atmosphere in the furnace due to burner heating in the actual rotary hearth furnace. .

The degree of collapse / pulverization of the pellets due to the reduction was judged by visual observation, among the total number of pellets (dry pellets) charged in the small heating furnace, that the original spherical shape was maintained after the reduction. It was judged by the ratio of the number of pellets (reduced iron) (this is defined as "shape retention rate").
In this experiment, 15 pellets were loaded into the small heating furnace at one time, but when 13 or more of these pellets maintained their original shape (that is, shape retention rate ≥ 86.7%), they collapsed.
When pulverization is effectively prevented and all of them maintain their original shape (that is, shape retention rate = 100%)
Was the optimum condition.

The results of this experiment are shown in FIG. FIG. 2 shows a region of each condition in which the combination of the surplus carbon ratio S _C and the mass ratio X _Q of the pseudo particles having a particle size of more than 1 mm is optimum, suitable or unsuitable. That is, the area P in FIG. 2 is an area under the preferable conditions, the area Q is an area under the optimum conditions, and the area P +
Areas other than the area Q are unsuitable areas in which pellets are often disintegrated and powdered. Further, the reduced iron produced under the conditions of the region P or the region Q showed higher values of dezincification rate and metallization rate than the reduced iron produced under the conditions of regions other than the region P + region Q.

From FIG. 2, the invention of claim 2 is derived from the portion corresponding to the area P + area Q, and the invention of claim 3 is derived from the portion corresponding to the area Q.

[0037]

[Table 1]

[0038]

As is apparent from the above description,
According to the present invention, it is possible to effectively prevent the disintegration and pulverization of pellets during reduction, and it is possible to produce a product reduced iron having a high dezincification rate and a high metallization rate with a high yield. Also,
The quality of zinc oxide recovered from the exhaust gas from the furnace is also significantly improved, and there is an effect that a zinc raw material with high utility value can be obtained.

[Brief description of drawings]

FIG. 1 is a diagram showing a schematic facility configuration for carrying out a reduced iron production method (crude zinc oxide production method) using blast furnace wet dust of the present invention.

FIG. 2 is a graph showing an optimum and suitable range capable of preventing disintegration and pulverization by combining a surplus carbon ratio S _C and a mass ratio X _Q of pseudo particles having a particle size of more than 1 mm.

FIG. 3 is a diagram showing a schematic flow of a dezincification / reduction treatment process of blast furnace wet dust using a rotary hearth furnace method according to a conventional method.

FIG. 4 is a microscopic view of powder contained in a product reduced iron produced by a conventional method.

[Explanation of symbols]

1 ... Crusher 2, 102 ... Mixer 3, 103 ... Granulator 4, 104 ... dryer 5, 105 ... Charging device 6, 106 ... Rotary hearth furnace 7,107 ... Burner 8, 108 ... Dust collector A: Wet blast furnace dust B ... Powdery raw material containing iron oxide

─────────────────────────────────────────────────── ─── Continued Front Page (51) Int.Cl. ⁷ Identification Code FI Theme Coat (Reference) C22B 7/02 C22B 7/02 A 19/30 19/30 19/34 19/34 (72) Inventor Iwasaki Nobuyuki 1 Kanazawa-machi, Kakogawa-shi, Hyogo Kadogawa Works, Kakogawa Works (72) Inventor Hidetoshi Tanaka 4-3-1 Bingocho, Chuo-ku, Osaka-shi, Osaka Kobe Steel Works, Osaka Branch (72) ) Inventor Kojiro Fuji 4-3 1-3 Bingo-cho, Chuo-ku, Osaka-shi, Osaka In-house Kobe Works, Kobe Steel Co., Ltd. (72) Inventor Hiroshi Sugitu 4 1-3 Bingo-cho, Chuo-ku, Osaka-shi, Osaka Company Kobe Works Osaka Branch F-term (reference) 4K001 AA10 AA30 BA02 BA14 CA20 CA21 CA23 GA07 GB01 GB09 HA01 4K012 DE01 DE03 DE08

Claims (6)

[Claims] 1. A crushing step of crushing blast furnace wet dust containing pseudo particles having a particle size of more than 1 mm so that the mass ratio of pseudo particles having a particle size of more than 1 mm in a mixed raw material is 50% or less.
To the crushed blast furnace wet dust, at least, a mixing step of mixing a powdery raw material containing iron oxide to form a mixed raw material, and an agglomeration step of agglomerating the mixed raw material to form an agglomerate, A reducing step of heating this agglomerate to dezincify / reduce it to obtain reduced iron; and a method for producing reduced iron using blast furnace wet dust. 2. A mass ratio X _Q (unit: mass%) of pseudo particles having a particle size of more than 1 mm in the mixed raw material and a surplus carbon rate S _C (unit: mass%) satisfy the following formula 1. Item 2. A method for producing reduced iron using the blast furnace wet dust according to Item 1. When 10 ≦ S _C ≦ 2, X _Q ≦ 50 2 <S _C ≦ 6, X _Q ≦ 70−10 · S _C where S _C = X _C − (12/16) · X _O (Note that X _C is a mass ratio (mass%) of carbon in the agglomerate after drying, and X _O is a ratio of oxygen of iron oxide and oxygen of zinc oxide in the agglomerate after drying. It is the ratio (mass%) of the total mass.) 3. A mass ratio X _Q (unit: mass%) of pseudo particles having a particle size of more than 1 mm in the mixed raw material and a surplus carbon rate S _C (unit: mass%) satisfy the following formula 2. Item 2. A method for producing reduced iron using the blast furnace wet dust according to Item 1. When the formula _{2 0 ≦ S C ≦ 1,} X Q ≦ 50 1 < When S _C ≦ 6, here _{X Q ≦ 60-10 · S C,} S C = X C - (12/16) · X O (Note that X _C is a mass ratio (mass%) of carbon in the agglomerate after drying, and X _O is a ratio of oxygen of iron oxide and oxygen of zinc oxide in the agglomerate after drying. It is the ratio (mass%) of the total mass.) 4. A drying step of drying the agglomerate between the agglomeration step and the charging step until the water content of the agglomerate becomes 1.0% by mass or less. 4. A method for producing reduced iron using the blast furnace wet dust according to any one of 3 above. 5. The blast furnace wet dust is dried to a predetermined water content so that the water content of the mixed raw material is 1.0 mass% or less.
A method for producing reduced iron using the blast furnace wet dust according to item. 6. A zinc recovery step for recovering the dezincified zinc component as crude zinc oxide is provided in addition to each step of the method for producing reduced iron according to claim 1. A method for producing crude zinc oxide using blast furnace wet dust, which comprises: