CN112322819A

CN112322819A - Rotary hearth furnace, method for using same, and method for producing reduced iron-containing material and zinc-containing material

Info

Publication number: CN112322819A
Application number: CN202011096495.4A
Authority: CN
Inventors: 中山俊孝; 岛真司; 野田悦郎; 福田良
Original assignee: Nippon Steel and Sumikin Engineering Co Ltd
Current assignee: Nippon Steel Engineering Co Ltd
Priority date: 2019-12-10
Filing date: 2020-10-14
Publication date: 2021-02-05
Also published as: JP2021092342A; JP7456762B2

Abstract

The invention provides a rotary hearth furnace, a method for using the rotary hearth furnace, and a method for producing reduced iron-containing material and zinc-containing material. The rotary hearth furnace is provided with: the combustion furnace comprises an annular hearth (11) having a burner, a rotary hearth (12) rotating inside the hearth (11), and an exhaust pipe (30) connected to the ceiling wall (11a) of the hearth (11). When the width and height of a furnace space (10) formed by a rotary hearth (12) and a hearth (11) are W and H, respectively, H/W is 0.4 or more.

Description

Rotary hearth furnace, method for using same, and method for producing reduced iron-containing material and zinc-containing material

Technical Field

The present application relates to a rotary hearth furnace, a method of using the rotary hearth furnace, and a method of producing a reduced iron-containing material and a zinc-containing material.

Background

In order to recover and utilize iron oxide contained in iron making waste, there is known a process of charging pellets obtained by kneading and granulating iron making waste with a reducing agent and a binder into a rotary hearth furnace and heating and reducing the pellets to produce reduced iron. In addition, there is known a process of recovering zinc as an oxide when treating iron-making waste containing zinc. This is a process in which zinc gasified by reduction is oxidized by oxygen in a furnace or an exhaust line to form solid zinc oxide, and the solid zinc oxide is recovered by a dust collector at the subsequent stage of an exhaust system.

In such a process, solid components contained in the exhaust gas may be fixed in the exhaust line. For this reason, patent document 1 (jp 2009-281617 a) proposes to control the exhaust flow rate in the exhaust pipe within a predetermined range so as to suppress adhesion of fine zinc oxide generated in the rotary hearth furnace to the exhaust pipe.

Disclosure of Invention

Problems to be solved by the invention

On the other hand, since the raw material to be treated in the rotary hearth furnace is derived from waste, the composition thereof is liable to vary. Once the composition changes, the strength of the agglomerates also changes. For example, as the volatile content increases, the strength of the agglomerates tends to decrease. When the strength is lowered, the iron component contained in the raw material is easily pulverized during heating in the rotary hearth furnace, and is scattered. When the amount of scattering increases, the yield of reduced iron may decrease, the purity of zinc oxide may decrease, and the productivity may decrease.

Means for solving the problems

To this end, in one aspect of the present application, a rotary hearth furnace and a method of using the same are provided that can improve the productivity of products. In one aspect of the present application, a method for producing a reduced iron-containing material is provided, which can improve the yield of reduced iron. In one aspect of the present application, a method for producing a zinc-containing material is provided, in which impurities contained in the zinc-containing material can be reduced.

A rotary hearth furnace according to one aspect of the present application includes: an annular hearth having a burner, a rotary hearth rotating inside the hearth, and an exhaust pipe connected to a top wall of the hearth; wherein, when the width and height of the furnace space formed by the rotary hearth and the hearth are W and H, respectively, H/W is 0.4 or more.

Since the H/W of the rotary hearth furnace is within a predetermined range, the iron content flowing into the exhaust pipe from the furnace space along with the exhaust gas can be reduced. This reduces the amount of iron extracted from the exhaust pipe with the exhaust gas, thereby improving the productivity of products such as reduced iron-containing materials. In addition, when zinc-containing materials contained in exhaust gas are recovered, the inclusion of iron components in the zinc-containing materials can be suppressed, and zinc-containing materials with reduced impurities can be produced.

In some embodiments of the rotary hearth furnace, when the length of the rising portion of the exhaust pipe is L and the inner diameter of the rising portion is D, L/D is preferably 6.5 or more. Thus, when the briquette including the iron-making dust and the char is subjected to the heat treatment, the iron component discharged from the exhaust pipe can be further reduced. In addition, when the zinc-containing material contained in the exhaust gas is recovered, the inclusion of iron components in the zinc-containing material can be further suppressed, and impurities in the zinc-containing material can be further reduced. Therefore, the productivity of the product can be further improved.

In some embodiments of the rotary hearth furnace, the flow velocity of the exhaust gas in the rising portion of the exhaust pipe is preferably 4.5 m/sec or more. Thus, when recovering the zinc-containing material contained in the exhaust gas, the recovery rate of the zinc-containing material can be increased, and the productivity of the product can be further increased.

In some embodiments, the rotary hearth furnace preferably includes: an introduction unit that introduces agglomerates containing electric furnace dust and a carbon material into the interior of the furnace chamber; a lead-out part for leading out the reduced iron-containing material from the rotary hearth; and a recovery unit that recovers zinc-containing materials contained in the exhaust gas on the downstream side of the exhaust pipe. The electric furnace dust contains a large amount of zinc oxide originating from plating. Therefore, the briquette containing the electric furnace dust is easily pulverized when heated. According to the rotary hearth furnace, scattering of iron components can be suppressed even if the briquette is pulverized, and reduced iron can be produced with high yield and zinc-containing material with reduced impurities can be produced.

A method for producing a reduced iron-containing material according to one aspect of the present application employs the rotary hearth furnace described in any one of the above, and the method for producing a reduced iron-containing material includes: heating the briquette comprising iron oxide and carbon material to reduce the iron oxide, thereby obtaining a reduced iron content containing reduced iron. In this production method, since the rotary hearth furnace described in any one of the above is used, the iron component discharged from the furnace space to the exhaust pipe is reduced, and the yield of reduced iron can be improved.

In some embodiments of the method for producing a reduced iron-containing material, the scattering rate of the iron component contained in the briquette is preferably 5% or less. This can further improve the yield of reduced iron.

A method for producing zinc-containing material according to an aspect of the present application employs any one of the rotary hearth furnaces described above, and the method for producing zinc-containing material includes the steps of: recovering zinc-containing material contained in exhaust gas obtained by heating an agglomerate comprising iron oxide, zinc oxide and carbon material. In this production method, since the rotary hearth furnace described in any of the above is used, the inclusion of iron in the zinc-containing material can be suppressed, and impurities in the zinc-containing material can be reduced.

In some embodiments, the zinc recovery rate is preferably 70% or more. Thereby, the productivity of zinc-containing materials can be improved. The content of iron in the zinc-containing material is preferably 8 mass% or less. Thus, impurities of the zinc-containing material can be further reduced.

A method of using a rotary hearth furnace according to an aspect of the present application uses a rotary hearth furnace including: the rotary hearth furnace comprises an annular hearth with a burner, a rotary hearth rotating inside the hearth, and an exhaust pipe connected to the top wall of the hearth. The using method comprises the following steps: an introduction step of introducing a briquette containing iron oxide and a carbon material onto a rotary hearth; a heating step of heating the briquette in a furnace space formed by the rotary hearth and the furnace chamber while rotating the rotary hearth to reduce the iron oxide; a discharge step of discharging the exhaust gas generated in the heating step from the furnace space through an exhaust pipe; and a lead-out step of leading out the reduced iron content from the rotary hearth. Further, when the width and height of the furnace space of the rotary hearth furnace are W and H, respectively, H/W is 0.4 or more.

In the above-described method of use, since the H/W is within the predetermined range, the exhaust gas flowing into the exhaust pipe in the exhaust step with the iron component can be suppressed. This reduces the amount of iron extracted from the exhaust pipe with the exhaust gas, thereby improving the productivity of the reduced iron content. In addition, when zinc-containing materials contained in exhaust gas are recovered, the inclusion of iron components in the zinc-containing materials can be suppressed, and zinc-containing materials with reduced impurities can be produced.

The method of using the rotary hearth furnace includes a recovery step of recovering the zinc-containing material from the exhaust gas flowing through the exhaust pipe, and in the exhaust step, the flow velocity of the exhaust gas in the portion of the exhaust pipe extending upward is preferably maintained at 4.5 m/sec or more. This improves the recovery rate of the zinc-containing material in the recovery step, and further improves the productivity of the product.

In one aspect of the present application, a rotary hearth furnace and a method of using the same can be provided that can improve the productivity of products. In one aspect of the present application, a method for producing a reduced iron-containing material is provided, which can improve the yield of reduced iron. In one aspect of the present application, a method for producing a zinc-containing material is provided, in which impurities contained in the zinc-containing material can be reduced.

Drawings

FIG. 1 is a view schematically showing one embodiment of a rotary hearth furnace.

FIG. 2 is a sectional view of the vicinity of a connecting portion between a furnace and an exhaust pipe of a rotary hearth furnace.

Fig. 3 is a graph showing an example of the relationship between the ratio of the height H to the width W of the furnace space and the content of iron in the zinc-containing material.

Fig. 4 is a graph showing an example of the relationship between the flow rate of exhaust gas and the zinc recovery rate.

FIG. 5 shows V²Graph showing an example of the relationship between the value of X (L/D) and the iron scattering rate.

Detailed Description

Hereinafter, embodiments of the present application will be described with reference to the drawings. The following embodiments are examples for illustrating the present application, and the present application is not limited to the following. In the drawings, the same features or features having the same functions are denoted by the same reference numerals, and redundant description thereof will be omitted as appropriate.

FIG. 1 is a view schematically showing one embodiment of a rotary hearth furnace. The rotary hearth furnace 100 includes: a hearth 11 formed by a ceiling wall 11a and side walls 11 b; a rotary hearth 12 rotating in the circumferential direction of the furnace 11 inside the furnace 11; an exhaust duct 30 connected to the ceiling wall 11a of the furnace 11; a gas cooling unit 35 connected to the downstream side of the exhaust pipe 30; and a recovery unit 40 connected to the downstream side of the gas cooling unit 35. The furnace 11 of fig. 1 is partially omitted to show its internal structure.

The annular furnace 11 has a plurality of burners 14 on both the outer and inner sides to heat the interior of the furnace 11. The burner 14 may be provided on only one of the outer side surface and the inner side surface. The rotary hearth 12 rotates inside the furnace 11 in the circumferential direction of the furnace 11.

The rotary hearth furnace 100 includes: a conveying unit 24 for conveying the briquette 22; an introduction part 21 that introduces the briquette 22 conveyed by the conveyance part 24 onto the rotary hearth 12; and a lead-out section 60 for leading out the reduced iron content from the rotary hearth 12. The introduction portion 21 is formed of, for example, a vibrating screen having slits. The agglomerates 22 are introduced through the slots of the vibrating screen onto the rotary hearth 12. The agglomerates 22 may include, for example, steelmaking dust, char, and a binder. When the briquette 22 contains electric furnace dust, a reduced iron-containing material containing reduced iron as a main component and a zinc-containing material containing zinc oxide as a main component can be produced as products in the rotary hearth furnace 100. The product is not limited to the above, and products other than the above may be produced, and only the reduced iron-containing material or only the zinc-containing material may be produced.

The rotary hearth furnace 100 may have a forming part for forming the briquette 22 on the upstream side of the conveying part 24. In the forming section, for example, iron oxide-containing dust, a carbon material, and a binder are kneaded, and the obtained kneaded mass is formed by a twin-roll forming machine to prepare a briquette 22 (formed body).

The iron oxide-containing dust may be iron-making dust, or may contain at least one of electric furnace dust, blast furnace dust, converter dust, and sintering dust. The dust may contain iron oxides, zinc oxide, and other constituents. The total iron content (t.fe) of the dust may be, for example, 10 to 60 mass%, and the ZnO content may be 2 to 40 mass%. The carbon material may be, for example, pulverized coal.

The briquette 22 introduced into the rotary hearth 12 is heated while moving inside the furnace 11 in accordance with the rotation of the rotary hearth 12. When the agglomerates 22 contain iron oxide and zinc oxide, a redox reaction represented by the following reaction formula occurs with heating. N may be any number, and may be 1, 2 or 3, for example. m may be any number, and may be, for example, 1, 3 or 4.

Fe_nO_m+mC→nFe+mCO

Fe_nO_m+mCO→nFe+mCO₂

ZnO+C→Zn+CO

ZnO+CO→Zn+CO₂

C+O₂→CO₂

C+CO₂→2CO

Iron oxides contained in the agglomerates are reduced to reduced iron. The reduced iron-containing material containing the reduced iron is discharged from the discharging section 60. The reduced iron-containing material is cooled by the cooling unit 62 and then used as a raw material for an electric furnace or the like. The exhaust gas discharged from the exhaust pipe 30 may carry zinc, iron, and oxides thereof. The exhaust gas discharged from the exhaust pipe 30 is cooled in the gas cooling portion 35.

In the recovery unit 40, solid components such as zinc oxide contained in the exhaust gas are captured and recovered. The recovery portion 40 may have, for example, a bag filter. The recovered solid component is a zinc-containing material containing zinc oxide as a main component. The zinc-containing material may contain a zinc compound such as zinc oxide, or may contain an iron component such as iron oxide. The gas obtained by removing the solid components in the recovery unit 40 is sucked by a blower 45 and discharged into the atmosphere through a stack 50, for example.

With reference to the introduction portion 21, the exhaust pipe 30 may be connected to the upstream side of the discharge portion 60 in the rotation direction of the rotary hearth 12, or may be connected to a position closer to the introduction portion 21 than the discharge portion 60. The gas in the furnace 11 can flow in the direction opposite to the rotating direction of the rotary hearth 12. In this case, the briquettes 22 rotating in the furnace 11 together with the rotary hearth 12 are in counter-current contact with the gas in the furnace 11 in the furnace space 10. By the countercurrent contact, the heating and reaction of the briquette 22 can be efficiently performed.

Fig. 2 is a sectional view of the rotary hearth furnace 100 of fig. 1 cut along a vertical plane parallel to the vertical direction and passing through the connection between the exhaust duct 30 and the furnace 11. Inside the furnace 11, a furnace space 10 is formed by the furnace 11 and the rotary hearth 12. The briquette 22 introduced from the introduction portion 21 is disposed on the rotary hearth 12. The rotary hearth 12 is supported by rollers 16 provided on the lower surface side thereof so as to be rotatable in the circumferential direction of the furnace 11. The briquette 22 is heated in the furnace space 10 while rotating together with the rotary hearth 12. The furnace space 10 is heated to, for example, 1000 to 1300 ℃. The following oxidation reaction occurs in the upper part of the furnace space 10.

2Zn+O₂→2ZnO

2Co+O₂→2CO₂

At least a part of the agglomerates 22 undergo pulverization through the above-described redox reaction. In particular, in the case where the agglomerates 22 contain zinc oxide, the pulverization progresses as the zinc is gasified.

The ratio (H/W) of the height H of the furnace space 10 to the width W of the furnace space 10 is 0.4 or more. The width W is the distance between the side walls inside the furnace 11. The height H is the distance between the upper surface of the rotary hearth 12 and the top surface 11c of the hearth 11. When the H/W is the above value, the inflow of the powdery material into the exhaust pipe 30 when the briquette 22 is heated and pulverized can be suppressed. From the viewpoint of further suppressing the inflow of the powdery material, H/W is preferably 0.5 or more, and may be 0.6 or more. From the viewpoint of effective utilization of the furnace space 10, the upper limit of H/W is preferably 2 or less, and may be 1.5 or less.

One end of the exhaust duct 30 is connected to the ceiling wall 11a of the furnace 11. The exhaust duct 30 includes a rising portion 31 extending upward from a connection portion with the furnace 11, and a horizontal portion 32 extending horizontally from a highest reaching point of the rising portion 31. The length of the rising portion 31, which is a portion of the exhaust pipe 30 extending upward from the lower end of the exhaust pipe 30, is L, and the inner diameter of the rising portion 31 of the exhaust pipe 30 is D.

The length L is a length along the center line CL of the exhaust pipe 30 from the height of the ceiling surface 11c of the furnace 11 to the highest reaching point of the rising portion 31. When the length L is long, the powder flowing from the furnace space 10 into the exhaust pipe 30 is decelerated by the rising portion 31 due to friction with the inner wall of the pipe, gravity, or the like, and easily falls down and returns to the furnace space 10. When the inner diameter D becomes smaller, the tube friction in the exhaust pipe 30 becomes larger, and the powder flowing from the furnace space 10 into the exhaust pipe 30 is easily returned to the furnace space 10. When the rising portion 31 of the exhaust pipe 30 is not a circular pipe or when the inner diameter D of the rising portion 31 changes, the equivalent diameter at the time of calculating the pressure loss is set as the inner diameter D of the rising portion 31, and the following L/D can be calculated.

If the ratio (L/D) of the length L to the inner diameter D is increased, the discharge of the pulverized material generated from the agglomerates 22 on the rotary hearth 12 to the downstream side with respect to the ascending portion 31 of the blast pipe 30 can be suppressed. As a result, the amount of reduced iron drawn out from the drawing-out portion 60 of the rotary hearth furnace 100 increases, and reduced iron can be produced in high yield. In addition, when the zinc-containing material is recovered from the exhaust gas discharged through the exhaust pipe 30, impurities such as iron components mixed in the zinc-containing material can be reduced.

The L/D is preferably 6.5 or more from the viewpoint of sufficiently improving the yield of reduced iron and sufficiently reducing impurities of zinc-containing materials. From the viewpoint of securing the installation site of the facility and improving the zinc recovery rate, the upper limit of L/D is preferably 30 or less, and may be 20 or less.

The iron content of a typical zinc ore is about 8 mass% (ZnS concentration is about 84 mass%). Therefore, the content of iron in the zinc-containing material is preferably 8 mass% or less, and may be 3 mass% or less, from the viewpoint of improving the added value of the zinc-containing material recovered from the exhaust gas of the rotary hearth furnace 100 as a product. The content of iron described herein is the total iron content (t.fe), and includes not only metallic iron but also iron contained in iron oxide and the like.

Since the zinc content of the electric furnace dust is high, when the dust contained in the briquette 22 is electric furnace dust, the briquette 22 is easily pulverized on the rotary hearth 12. Therefore, it is estimated how much the scattering rate Φ of the iron contained in the nuggets 22 needs to be suppressed in order to control the iron content in the zinc-containing material to 8 mass% or less as follows.

Assuming that the mass of the electric furnace dust contained in the briquette is B, the iron content of the electric furnace dust is x (mass%), the zinc oxide content of the electric furnace dust is z (mass%), the iron content of the zinc oxide recovered in the rotary hearth furnace 100 is y (mass%), and the scattering rate of iron (i.e., iron contained in the electric furnace dust) contained in the briquette 22 is Φ, the following relationship holds when all the zinc oxide contained in the electric furnace dust is recovered in the recovery portion 40. Here, the iron scattering rate Φ is a ratio of iron (t.fe) mixed into the zinc-containing material out of iron (t.fe) contained in the electric furnace dust.

y＝B·x·φ/(B·z+B·x·φ)

＝x·φ/(z+x·φ)

The iron scattering rate Φ when the iron content of the zinc-containing material is the same as the iron content of the zinc ore, that is, when y is 8 mass%, is calculated as follows using the above equation. Wherein x and z are 40 mass% and 25 mass%, respectively, as the iron content and the zinc oxide content in the electric furnace dust.

8 mass% ([ 40 mass% × Φ/(25 mass% +40 mass% × Φ) ] × 100

φ＝2/36.8×100≈0.05＝5％

From the above-mentioned relational expression, it is understood that when the iron scattering rate Φ contained in the electric furnace dust (agglomerate 22) is controlled to 5% or less in the case of recovering the zinc-containing material from the exhaust gas, the zinc-containing material having the same iron concentration as or lower than that of the zinc ore can be recovered. The scattering rate of iron contained in the briquette 22 is preferably 4% or less, and may be 3% or less.

The flow velocity of the exhaust gas in the rising portion 31 of the exhaust pipe 30 is preferably maintained at 4.5 m/sec or more, for example, and may be maintained at 6 m/sec or more. When the flow rate of the exhaust gas is maintained at a high level, the recovery rate of the zinc-containing material can be improved in the case of recovering the zinc-containing material from the exhaust gas. On the other hand, when the flow rate of the exhaust gas is too high, the incorporation of iron into the zinc-containing material tends to increase, and the yield of reduced iron tends to decrease. Therefore, the flow velocity of the exhaust gas in the rising portion 31 of the exhaust pipe 30 may be less than 9 m/sec.

Next, an embodiment of a method of using the rotary hearth furnace 100 will be described below by taking as an example a case of using the rotary hearth furnace. The description of the rotary hearth furnace 100 can be applied to the following method of use. The following description of the method of use is also applicable to the rotary hearth furnace 100.

The method of use of this example includes the following steps: an introduction step of introducing the briquette 22 containing iron oxide and a carbon material onto the rotary hearth 12; a heating step of heating the briquette 22 in the furnace space 10 while rotating the rotary hearth 12 to reduce the iron oxide; a discharge step of discharging the exhaust gas generated in the heating step from the furnace space 10 through the exhaust pipe 30; a lead-out step of leading out the reduced iron-containing material from the rotary hearth 12; and a recovery step of recovering the zinc-containing material from the discharged exhaust gas through the exhaust pipe 30.

The introduction step can be performed by the introduction section 21 in fig. 1. The mass 22 may comprise: dust containing iron oxide, coal and other carbon materials, and a binder. In the introduction step, the briquette 22 is continuously introduced onto the rotary hearth 12. The introduction step may be preceded by a forming step of kneading the iron oxide and zinc oxide-containing dust, the char, and the binder, and forming the resultant kneaded mass with a twin-roll forming machine to obtain the briquette 22.

In the heating process, the briquette 22 is heated by radiant heat from the burner 14. Thereby, the oxidation-reduction reaction represented by the above reaction formula occurs. As these reactions proceed, voids are created in the agglomerates 22 and at least a portion of the pulverization occurs. A part of the powder may flow into the exhaust pipe 30 from the furnace space 10 along with the exhaust gas in the exhaust step. However, since the H/W of the furnace space 10 of the rotary hearth furnace 100 used in this example is 0.4 or more, the iron component flowing from the furnace space 10 into the exhaust pipe 30 can be sufficiently reduced. Therefore, the waste of reduced iron can be reduced, and the yield of reduced iron can be improved. Further, the zinc-containing material recovered in the recovery step can be inhibited from being contaminated with iron components, and a zinc-containing material with reduced impurities can be produced.

In the exhaust step, the exhaust gas generated in the heating step is exhausted to the downstream side of the exhaust pipe 30 through the exhaust pipe 30 connected to the ceiling wall 11a of the furnace 11. The flow velocity of the exhaust gas in the rising portion 31 of the exhaust pipe 30 is preferably maintained in the above range. In this case, L/D is preferably 6.5 or more. This improves the recovery rate of the zinc-containing material recovered in the recovery step, and reduces the contamination of iron components into the zinc-containing material.

In the discharging step, the reduced iron content is discharged from the rotary hearth 12. The metallization ratio of iron in the reduced iron-containing material is preferably 70% or more, for example. The discharged reduced iron-containing material is cooled by the cooling unit 62 and then used as a raw material for an electric furnace or the like.

In the recovery step, the zinc-containing material is recovered by using a recovery unit 40 having, for example, a bag filter. By increasing the flow rate of the exhaust gas in the rising section 31 in the discharging step, the recovery rate of the zinc-containing material can be increased. The zinc recovery rate is preferably 70% or more, and may be 80% or more. The zinc recovery rate is a ratio of the amount of zinc contained in the zinc-containing material recovered in the recovery step (in terms of metallic zinc) to the amount of zinc contained in the agglomerate 22 (in terms of metallic zinc).

According to the above-mentioned method of use, scattering of iron components to the outside of the furnace space 10 can be suppressed, and the iron components can be sufficiently taken into the reduced iron content obtained in the drawing step and recovered. Therefore, the reduced iron-containing material can be produced in high yield. Further, the zinc component contained in the briquette can be sufficiently taken into the zinc-containing material recovered in the recovery step and recovered. In addition, the iron component mixed in the zinc-containing material can be reduced, and the zinc purity in the zinc-containing material can be fully improved. In the present use method, both the reduced iron-containing material and the zinc-containing material are produced as the product, but in other cases, only the reduced iron-containing material may be produced as the product without recovering the zinc-containing material in the recovering step. In this case, the dust used for making the briquette may be free of zinc oxide. In still other examples, only the zinc-containing material may be manufactured as an article.

One embodiment of the method for producing a reduced iron-containing material includes the steps of: the briquette 22 including the iron oxide and the char material is heated using the rotary hearth furnace 100 to reduce the iron oxide, thereby obtaining a reduced iron content containing reduced iron. In this manufacturing method, since the rotary hearth furnace 100 is used, scattering of iron components from the furnace space 10 can be suppressed. Therefore, the reduced iron-containing material can be produced in high yield. The scattering rate of iron contained in the briquette 22 is preferably 5% or less, for example, and may be 4% or less. The reduced iron content may further contain iron oxide. The metallization ratio of iron in the reduced iron-containing material is preferably 70% or more, for example. The description of the rotary hearth furnace 100 and the method of using the same can be applied to the method of producing a reduced iron-containing material according to the present embodiment.

One embodiment of the method for producing a zinc-containing material comprises the following steps: the briquette 22 containing iron oxide, zinc oxide and carbon material is heated using the rotary hearth furnace 100, and the zinc-containing material contained in the exhaust gas obtained thereby is recovered by the recovery unit 40 on the downstream side of the exhaust pipe 30. In this manufacturing method, since the rotary hearth furnace 100 is used, scattering of iron components from the furnace space 10 can be suppressed. Therefore, a zinc-containing material in which the mixing of iron components is suppressed can be produced.

The metallic zinc that has been reduced when scattered in the furnace space 10 is re-oxidized by oxygen in the exhaust gas, and is cooled by the gas cooling unit 35 provided between the recovery unit 40 and the exhaust pipe 30. The content of iron and iron compounds in the zinc-containing material is preferably 8 mass% or less, more preferably 3 mass% or less, and still more preferably 1 mass% or less in terms of iron. The description of the rotary hearth furnace 100 and the method of using the same can be applied to the method of manufacturing the zinc-containing material according to the present embodiment.

The above describes some embodiments of the present application, and the present application is not limited to the above embodiments. For example, in the rotary hearth furnace 100, the rising portion 31 of the exhaust pipe 30 is connected to the horizontal portion 32, but the present invention is not limited thereto. For example, in the modification, the rising portion 31 may be connected to the falling portion that falls from the highest arrival point, and may have an inverted U-shape, instead of being connected to the horizontal portion 32. Note that even if there are second or more rising portions rising along the flow direction of the exhaust gas on the downstream side with respect to the horizontal portion 32 (or the falling portion), the length of the portion is not included in the above-mentioned L. This is because, even if the iron component or the like falls back in the second or more ascenders, it cannot be guaranteed to return into the furnace space 10.

In addition, when the amount of zinc contained in the briquette is small, the zinc-containing material may not be recovered in the rotary hearth furnace and the method of using the rotary hearth furnace. In this case, only the reduced iron-containing material can be produced as a product by using a rotary hearth furnace. The burners 14 may be provided only on either one side of the furnace 11, instead of both the inside and the outside of the furnace.

Examples the contents of the present application will be explained in more detail with reference to the following examples and comparative examples, but the present application is not limited to the following examples at all.

(example 1, comparative example 1)

As shown in Table 1, various rotary hearth furnaces having different widths W and heights H were prepared. Any rotary hearth furnace has the structure shown in fig. 1 and 2. The briquette is made from electric furnace dust, pulverized coal and a binder. The agglomerates are introduced into a rotary hearth furnace to produce a reduced iron-containing material and a zinc-containing material. When each rotary hearth furnace was used, the content of iron contained in the zinc-containing material recovered by the bag filter (recovery unit 40) provided on the downstream side of the exhaust pipe 30 was analyzed. The content of iron is the total iron content (t.fe), and includes not only metallic iron but also iron contained in iron oxide and the like. This content was obtained by chemical analysis. The results are shown in table 1 and fig. 3.

[ Table 1]

As shown in table 1 and fig. 3, it was confirmed that the content of iron in the zinc-containing material recovered by the bag filter was sufficiently reduced by setting the H/W to a predetermined value or more.

Example 2 as shown in table 2, a plurality of types of rotary hearth furnaces having cylindrical exhaust pipes 30 with different internal cross-sectional areas were prepared. Any rotary hearth furnace has the structure shown in fig. 1 and 2. The briquette is made from electric furnace dust, pulverized coal and a binder. The agglomerates are introduced into a rotary hearth furnace to produce a reduced iron-containing material and a zinc-containing material. The zinc recovery rate was determined for each rotary hearth furnace. As the briquette, a material made of electric furnace dust, pulverized coal and a binder was used. The zinc recovery rate is a ratio of the amount of zinc (in terms of metallic zinc) contained in the zinc-containing material recovered by the bag filter (recovery unit 40) to the amount of zinc (in terms of metallic zinc) contained in the agglomerate. The results are shown in table 2 and fig. 4.

[ Table 2]

As shown in table 2 and fig. 4, it was confirmed that the zinc recovery rate was increased by increasing the flow rate of the exhaust gas. As is clear from fig. 4, when the flow rate of the exhaust gas was maintained at 4.5 m/sec or more, the zinc recovery rate was 80% or more.

In example 3, as shown in table 3, a plurality of types of rotary hearth furnaces in which the inner diameter D of the exhaust pipe 30 and the length L of the rising portion 31 of the exhaust pipe 30 are different were prepared. Any rotary hearth furnace has the structure shown in fig. 1 and 2. The briquette is made from electric furnace dust, pulverized coal and a binder. The agglomerates are introduced into a rotary hearth furnace to produce a reduced iron-containing material and a zinc-containing material. The iron scattering rate phi was determined when each rotary hearth furnace was used. The iron scattering rate Φ is a ratio of the total iron amount (t.fe) contained in the zinc-containing material recovered by the bag filter (recovery unit 40) to the total iron amount (t.fe) contained in the briquette. The results are shown in table 3 and fig. 5. In Table 3 are shownFlow velocity V of exhaust gas, and factor V constituting friction coefficient of pipe²Calculated value of X (L/D). FIG. 5 shows a horizontal axis V²X (L/D) and the ordinate are a logarithmic graph of the iron scattering rate.

[ Table 3]

As shown in Table 3 and FIG. 5, the factor V constituting the friction coefficient of the pipe was confirmed²When X (L/D) is larger, the iron scattering rate φ becomes smaller. This means that the iron component once flowed into the rising part 31 of the exhaust pipe 30 from the furnace space 10 returns to the furnace space 10 by the influence of friction with the inner wall of the rising part 31 and is recovered as the reduced iron content. As shown in fig. 5, V when the iron scattering rate Φ is 5%²The value of x (L/D) is 132. That is, when using the briquette containing electric furnace dust, the operating conditions are set so that V²The value of x (L/D) reaches 132 (m)²Second/second²) In the above case, the iron content mixed in the recovered zinc-containing material can be sufficiently reduced.

As is clear from the results of table 2 and fig. 4 of example 2, the flow velocity V of the exhaust gas needs to be maintained at 4.5 m/sec or more in order to improve the zinc recovery rate. In order to sufficiently reduce the iron component mixed in the recovered zinc-containing material, V derived from Table 3 and FIG. 5²×(L/D)≥132(m²Second/second²) In the relational expression (2), when V is substituted to 4.5 m/sec, L/D is not less than 6.5. Therefore, it can be said that L/D is preferably 6.5 or more.

Claims

1. A rotary hearth furnace comprising: an annular furnace chamber having a burner, a rotary hearth rotating inside the furnace chamber, and an exhaust pipe connected to a ceiling wall of the furnace chamber,

when the width and height of the furnace space formed by the rotary hearth and the hearth are W and H, respectively, H/W is 0.4 or more.

2. The rotary hearth furnace according to claim 1, wherein L/D is 6.5 or more when L is a length of a rising portion of the exhaust pipe and D is an inner diameter of the rising portion.

3. The rotary hearth furnace according to claim 1 or 2, wherein a flow velocity of the exhaust gas in the rising portion of the exhaust pipe is 4.5 m/sec or more.

4. The rotary hearth furnace according to claim 1 or 2, comprising:

an introduction part that introduces a briquette containing electric furnace dust and a char material onto the rotary hearth;

a discharge section for discharging the reduced iron-containing material from the rotary hearth; and

and a recovery unit for recovering zinc-containing material contained in the exhaust gas on the downstream side of the exhaust pipe.

5. The rotary hearth furnace according to claim 3, comprising:

6. A method for producing a reduced iron-containing material using the rotary hearth furnace according to any one of claims 1 to 5, comprising:

heating the briquette comprising iron oxide and carbon material to reduce the iron oxide, thereby obtaining a reduced iron content containing reduced iron.

7. The method of producing a reduced iron-containing material according to claim 6, wherein a scattering rate of iron contained in the briquette is 5% or less.

8. A method for producing a zinc-containing material using the rotary hearth furnace according to any one of claims 1 to 5, comprising:

recovering zinc-containing material contained in exhaust gas obtained by heating an agglomerate comprising iron oxide, zinc oxide and carbon material.

9. The method for producing a zinc-containing material according to claim 8, wherein a zinc recovery rate is 70% or more.

10. The method for producing a zinc-containing material according to claim 8 or 9, wherein the content of iron in the zinc-containing material is 8 mass% or less.

11. A method of using a rotary hearth furnace, the rotary hearth furnace comprising: the use method of the furnace comprises an annular hearth having a burner, a rotary hearth rotating inside the hearth, and an exhaust pipe connected to a ceiling wall of the hearth, and comprises the steps of:

an introduction step of introducing a briquette containing iron oxide and a carbon material onto the rotary hearth;

a heating step of heating the briquette in a furnace space formed by a rotary hearth and a furnace while rotating the rotary hearth to reduce the iron oxide;

a discharge step of discharging the exhaust gas generated in the heating step from the furnace space through the exhaust pipe; and

a lead-out step of leading out the reduced iron-containing material from the rotary hearth,

when the width and height of the furnace space are W and H, respectively, H/W is 0.4 or more.

12. The method of using a rotary hearth furnace according to claim 11, having: a recovery step of recovering a zinc-containing material from the exhaust gas flowing through the exhaust pipe,

in the exhaust step, the flow velocity of the exhaust gas in the portion of the exhaust pipe extending upward is maintained at 4.5 m/sec or more.