JP2021092342A - Rotary hearth furnace, method for using the same and method for producing reduced iron-contained material and zinc-contained material - Google Patents

Abstract

To provide a rotary hearth furnace capable of improving the productivity of products.SOLUTION: A rotary hearth furnace comprises an annular furnace body 11 having a burner, a rotary hearth 12 rotating the inside of the furnace body 11 and an exhaust gas pipe 30 connected to a ceiling wall 11a of the furnace body 11. Provided that the width and height of a furnace inner space 10 composed of the rotary hearth 12 and the furnace body 11 are defined as W and H, respectively, H/W is 0.4 or more.SELECTED DRAWING: Figure 2

Description

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

In order to reuse iron oxide contained in iron-making waste, the process of producing reduced iron by kneading iron-making waste with a reducing agent and binder, charging pellets into a rotary hearth furnace, and heating and reducing them. It has been known. In addition, when treating iron-making waste containing zinc, a process of recovering zinc as an oxide is also known. This is a process in which zinc vaporized by reduction is oxidized by oxygen in the furnace or an exhaust gas duct to form solid zinc oxide, which is recovered by a dust collector at the subsequent stage of the exhaust gas system.

In such a process, the solid content contained in the exhaust gas may stick in the exhaust gas duct. Therefore, Patent Document 1 proposes to set the exhaust gas flow velocity in the exhaust gas duct within a predetermined range in order to suppress the adhesion of fine zinc oxide generated in the rotary hearth furnace in the exhaust gas duct. ..

Japanese Unexamined Patent Publication No. 2009-281617

By the way, since the raw material processed in the rotary hearth furnace is derived from waste, the composition is liable to fluctuate. As the composition fluctuates, so does the strength of the briquette. For example, as the volatile content increases, the strength of the briquette tends to decrease. When the strength is low, iron contained in the raw material is likely to be scattered by being pulverized during heating in the rotary hearth furnace. If the amount of scattering is large, there is a concern that the yield of reduced iron may decrease or the purity of zinc oxide may decrease, resulting in a decrease in productivity.

Therefore, the present disclosure provides, in one aspect, a rotary hearth furnace capable of improving the productivity of manufactured products and a method of using the same. The present disclosure provides, in one aspect, a method for producing a reduced iron-containing material capable of improving the yield of reduced iron. The present disclosure provides, in one aspect, a method for producing a zinc-containing material capable of reducing impurities contained in the zinc-containing material.

The rotary hearth furnace according to one aspect of the present disclosure includes a rotary hearth having a burner, a rotary hearth that rotates inside the furnace body, and an exhaust gas pipe connected to the ceiling wall of the furnace body. In a hearth furnace, the H / W is 0.4 or more, where W and H are the widths and heights of the furnace space composed of the rotary hearth and the furnace body, respectively.

Since the H / W of the above-mentioned rotary hearth furnace is within a predetermined range, it is possible to reduce the iron content that accompanies the exhaust gas and flows into the exhaust gas pipe from the space inside the furnace. As a result, the iron content derived from the exhaust gas pipe along with the exhaust gas is reduced, and the productivity of manufactured products such as reduced iron-containing substances can be improved. Further, when recovering the zinc-containing material contained in the exhaust gas, it is possible to suppress the mixing of iron into the zinc-containing material and produce a zinc-containing material having reduced impurities.

In some embodiments, the above-mentioned rotary hearth furnace has an L / D of 6.5 or more, where L is the length of the rising portion of the exhaust gas pipe and D is the inner diameter of the rising portion. You can. As a result, when the briquette containing iron-making dust and charcoal is heat-treated, the iron content derived from the exhaust gas pipe can be further reduced. Further, when recovering the zinc-containing material contained in the exhaust gas, it is possible to further suppress the mixing of iron into the zinc-containing material and further reduce the impurities of the zinc-containing material. Therefore, the productivity of the manufactured product can be further improved.

In some embodiments, the above-mentioned rotary hearth furnace may have an exhaust gas flow velocity of 4.5 m / sec or more at the rising portion of the exhaust gas pipe. As a result, when the zinc-containing material contained in the exhaust gas is recovered, the recovery rate of the zinc-containing material can be increased, and the productivity of the manufactured product can be further improved.

In some embodiments, the above-mentioned rotary hearth furnace has an introduction part for introducing a briquette containing electric furnace dust and a carbonaceous material into the furnace body, and a derivation for deriving a reduced iron-containing material from above the rotary hearth. A unit and a recovery unit for recovering zinc-containing substances contained in the exhaust gas may be provided on the downstream side of the exhaust gas pipe. Electric furnace dust contains a large amount of zinc oxide derived from plating. Therefore, briquettes containing electric furnace dust tend to be pulverized when heated. In the rotary hearth furnace, even if the briquette is pulverized, the scattering of iron is suppressed, and it is possible to produce a zinc-containing material with reduced impurities while producing reduced iron in a high yield.

The method for producing a reduced iron-containing material according to one aspect of the present disclosure is the method for producing a reduced iron-containing material using the rotary hearth furnace according to any one of the above, and heats a briquette containing iron oxide and a carbonaceous material. Then, it has a step of obtaining a reduced iron-containing material containing reduced iron by reducing iron oxide. Since the rotary hearth furnace described in any of the above is used in this manufacturing method, the iron content led out from the space inside the furnace to the exhaust gas pipe can be reduced, and the yield of reduced iron can be improved.

In the above-mentioned method for producing a reduced iron-containing material, in some embodiments, the scattering rate of iron contained in the briquette may be 5% or less. Thereby, the yield of reduced iron can be further improved.

The method for producing a zinc-containing material according to one aspect of the present disclosure is the method for producing a zinc-containing material using the rotary hearth furnace according to any one of the above, and a briquette containing iron oxide, zinc oxide and a carbonaceous material is used. It has a step of recovering zinc-containing substances contained in the exhaust gas obtained by heating. Since the rotary hearth furnace described in any of the above is used in this production method, it is possible to suppress the mixing of iron into the zinc-containing material and reduce the impurities of the zinc-containing material.

In the above-mentioned method for producing a zinc-containing product, the zinc recovery rate may be 70% or more in some embodiments. Thereby, the productivity of the zinc-containing material can be improved. Further, the iron content in the zinc-containing material may be 8% by mass or less. Thereby, impurities of the zinc-containing material can be further reduced.

The method of using the rotary hearth furnace according to one aspect of the present disclosure includes an annular furnace body having a burner, a rotary hearth rotating inside the furnace body, an exhaust gas pipe connected to the ceiling wall of the furnace body, and the like. Use a rotary hearth furnace equipped with. This usage method involves the introduction process of introducing a briquette containing iron oxide and charcoal on the rotary hearth, and heating the briquette in the furnace space composed of the rotary hearth and the furnace body while rotating the rotary hearth. A heating step for reducing iron oxide, a discharge step for discharging the exhaust gas generated in the heating step from the furnace space through an exhaust gas pipe, and a derivation step for deriving the reduced iron-containing material from the top of the rotating hearth. Has. When the width and height of the space inside the rotary hearth furnace are W and H, respectively, the H / W is 0.4 or more.

In the above usage method, since the H / W is within a predetermined range, it is possible to suppress the iron content accompanying the exhaust gas flowing into the exhaust gas pipe in the discharge process. As a result, the iron content derived from the exhaust gas pipe along with the exhaust gas is reduced, and the productivity of the reduced iron-containing material can be improved. Further, when recovering the zinc-containing material contained in the exhaust gas, it is possible to suppress the mixing of iron into the zinc-containing material and produce a zinc-containing material having reduced impurities.

The method of using the rotary hearth furnace described above includes a recovery step of recovering zinc-containing substances from the exhaust gas flowing through the exhaust gas pipe, and in the discharge step, the flow velocity of the exhaust gas in the portion extending above the exhaust gas pipe is 4.5 m /. May be maintained for more than a second. As a result, the recovery rate of the zinc-containing material in the recovery step can be increased, and the productivity of the manufactured product can be further improved.

The present disclosure can provide, in one aspect, a rotary hearth furnace capable of improving the productivity of a product and a method of using the same. The present disclosure provides, in one aspect, a method for producing a reduced iron-containing material capable of improving the yield of reduced iron. The present disclosure provides, in one aspect, a method for producing a zinc-containing material capable of reducing impurities contained in the zinc-containing material.

FIG. 1 is a diagram schematically showing an embodiment of a rotary hearth furnace. FIG. 2 is a cross-sectional view of the vicinity of the connection portion between the furnace body of the rotary hearth furnace and the exhaust gas pipe. FIG. 3 is a graph showing an example of the relationship between the ratio of the same height H to the width W of the furnace space and the iron content in the zinc-containing material. FIG. 4 is a graph showing an example of the relationship between the flow velocity of exhaust gas and the zinc recovery rate. FIG. 5 is ^{a graph showing an example of the relationship between the value of V 2} × (L / D) and the scattering rate of iron.

Hereinafter, embodiments of the present disclosure will be described with reference to the drawings as the case may be. However, the following embodiments are examples for explaining the present disclosure, and are not intended to limit the present disclosure to the following contents. In each drawing, the same reference numerals are used for the same elements or elements having the same function, and duplicate description may be omitted in some cases.

FIG. 1 is a diagram schematically showing an embodiment of a rotary hearth furnace. The rotary hearth furnace 100 includes a furnace body 11 composed of a ceiling wall 11a and a side wall 11b, a rotary hearth 12 that rotates inside the furnace body 11 along the circumferential direction of the furnace body 11, and a furnace body 11. An exhaust gas pipe 30 connected to the ceiling wall 11a, a gas cooling unit 35 connected to the downstream side of the exhaust gas pipe 30, and a recovery unit 40 connected to the downstream side of the gas cooling unit 35 are provided. The furnace body 11 of FIG. 1 is partially cut out to show its internal structure.

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

The rotary hearth furnace 100 includes a transport unit 24 that conveys the briquette 22, an introduction unit 21 that introduces the briquette 22 conveyed by the transport unit 24 onto the rotary hearth 12, and a reduced iron-containing material from the rotary hearth 12. It is provided with a derivation unit 60 for deriving the above. The introduction unit 21 is composed of, for example, a vibrating sieve having a slit. The briquette 22 passes through the slit of the vibrating sieve and is introduced onto the rotary hearth 12. The briquette 22 may contain, for example, steelmaking dust, carbonaceous material and binder. When the briquette 22 contains electric furnace dust, the rotary hearth furnace 100 manufactures a reduced iron-containing product containing reduced iron as a main component and a zinc-containing product containing zinc oxide as a main component as manufactured products. May be good. However, the manufactured products are not limited, and products other than these may be produced, or only reduced iron-containing products or only zinc-containing products may be produced.

The rotary hearth furnace 100 may have a molding portion for molding the briquette 22 on the upstream side of the transport portion 24. In the molding section, for example, a briquette 22 (molded body) is manufactured by molding a kneaded product obtained by kneading dust containing iron oxide, a carbonaceous material, and a binder with a double roll molding machine.

The dust containing iron oxide may be iron-making dust, and may contain at least one of electric furnace dust, blast furnace dust, converter dust, and sintered dust. The dust may contain iron oxide, zinc oxide and other components. The total iron content (T.Fe) of the dust may be, for example, 10 to 60% by mass, and the ZnO content may be 2 to 40% by mass. The charcoal material may be, for example, pulverized coal.

The briquette 22 introduced on the rotary hearth 12 is heated while moving inside the furnace body 11 as the rotary hearth 12 rotates. When the briquette 22 contains iron oxide and zinc oxide, the redox reaction represented by the following reaction formula proceeds with heating. In addition, n may be an arbitrary numerical value, and may be 1, 2, or 3, for example. m may be any numerical value, for example 1, 3 or 4.

Fe _n O _m + mC → nFe + mCO
Fe _n O _m + mCO → nFe + mCO ₂
ZnO + C → Zn + CO
ZnO + CO → Zn + CO ₂
C + O ₂ → CO ₂
C + CO ₂ → 2CO

Iron oxide contained in briquettes is reduced to reduced iron. A reduced iron-containing material containing reduced iron is derived from the out-licensing unit 60. The reduced iron-containing material may be used as a raw material for, for example, an electric furnace after being cooled by the cooling unit 62. Zinc, iron and oxides thereof may accompany the exhaust gas discharged from the exhaust gas pipe 30. The exhaust gas discharged from the exhaust gas pipe 30 is cooled by the gas cooling unit 35.

The recovery unit 40 captures and recovers solids such as zinc oxide contained in the exhaust gas. The collection unit 40 may have, for example, a bug filter. The recovered solid content is a zinc-containing substance containing zinc oxide as a main component. This zinc-containing material may contain a zinc compound such as zinc oxide, or may contain iron such as iron oxide. The gas obtained by removing the solid content in the recovery unit 40 is sucked by the blower 45 and released to the atmosphere by the chimney 50, for example.

The exhaust gas pipe 30 may be connected to the upstream side of the rotary hearth 12 in the rotation direction with reference to the introduction unit 21, and may be connected closer to the introduction unit 21 than the outlet unit 60. The gas in the furnace body 11 may flow in the direction opposite to the rotation direction of the rotary hearth 12. In this case, the briquette 22 rotating in the furnace body 11 together with the rotary hearth 12 and the gas in the furnace body 11 come into countercurrent contact with each other in the furnace body space 10. By the countercurrent contact, the heating and reaction of the briquette 22 can proceed efficiently.

FIG. 2 is a cross-sectional view of the rotary hearth furnace 100 of FIG. 1 when it is cut in a vertical plane parallel to the vertical direction and passing through a connection portion between the exhaust gas pipe 30 and the furnace body 11. Inside the furnace body 11, there is a furnace space 10 composed of the furnace body 11 and the rotary hearth 12. The briquette 22 introduced from the introduction unit 21 is arranged on the rotary hearth 12. The rotary hearth 12 is rotatably supported along the circumferential direction of the furnace body 11 by traveling wheels 16 provided on the lower surface side thereof. 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 ° C. In the upper part of the furnace space 10, for example, the following oxidation reaction proceeds.
2Zn + O ₂ → 2ZnO
2Co + O ₂ → 2CO ₂

At least a part of the briquette 22 is pulverized by the above-mentioned redox reaction. In particular, when the briquette 22 contains zinc oxide, pulverization is promoted with the vaporization of zinc.

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 inner side walls of the furnace body 11. The height H is the distance between the upper surface of the rotary hearth 12 and the ceiling surface 11c of the furnace body 11. Since the H / W has the above-mentioned value, it is possible to prevent the powdery substance when the briquette 22 is heated and pulverized from flowing into the exhaust gas pipe 30. From the viewpoint of further suppressing the inflow of powdery substances, the H / W may be 0.5 or more, and may be 0.6 or more. The upper limit of H / W may be 2 or less, or 1.5 or less, from the viewpoint of effectively utilizing the space in the furnace 10.

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

The length L is a length along the center line CL of the exhaust gas pipe 30 from the height of the ceiling surface 11c of the furnace body 11 to the highest reaching point of the ascending portion 31. When this length L becomes long, the powdery substance that has flowed into the exhaust gas pipe 30 from the furnace space 10 decelerates due to the influence of friction with the pipe inner wall and gravity in the ascending portion 31, and falls to the furnace space. It becomes easy to return to 10. When the inner diameter D becomes smaller, the pipe friction in the exhaust gas pipe 30 becomes larger, and the powdery substance flowing into the exhaust gas pipe 30 from the furnace space 10 easily returns to the furnace space 10. When the rising portion 31 of the exhaust gas pipe 30 is not a circular pipe, or when the inner diameter D changes in the rising portion 31, the equivalent diameter when calculating the pressure loss is set as the inner diameter D of the rising portion 31 as follows. L / D can be calculated.

If the ratio (L / D) of the length L to the inner diameter D is increased, the powdered material generated from the briquette 22 on the rotary hearth 12 is discharged to the downstream side of the rising portion 31 of the exhaust gas pipe 30. Is suppressed. As a result, the amount of reduced iron derived from the lead-out unit 60 of the rotary hearth furnace 100 is increased, and the reduced iron can be produced in a high yield. Further, when the zinc-containing material is recovered from the exhaust gas discharged through the exhaust gas pipe 30, impurities such as iron mixed in the zinc-containing material can be reduced.

The L / D may be 6.5 or more from the viewpoint of sufficiently reducing impurities in the zinc-containing material while sufficiently increasing the yield of reduced iron. The upper limit of L / D may be 30 or less, or 20 or less, from the viewpoint of securing the installation location of the equipment and increasing the zinc recovery rate.

The iron content of a typical zinc ore is about 8% by weight (ZnS concentration is about 84% by weight). Therefore, from the viewpoint of increasing the added value of the zinc-containing material recovered from the exhaust gas of the rotary hearth furnace 100 as a manufactured product, the iron content in the zinc-containing material may be 8% by mass or less, and may be 3% by mass. It may be less than or equal to%. The iron content referred to here is the total iron content (TF) including not only metallic iron but also iron contained in iron oxide and the like.

Since the electric furnace dust has a high zinc content, when the dust contained in the briquette 22 is electric furnace dust, the briquette 22 is likely to be pulverized on the rotary hearth 12. Therefore, in order to reduce the iron content in the zinc-containing material to 8% by mass or less, it is estimated below to what extent it is necessary to suppress the iron scattering rate φ contained in the briquette 22.

The amount of 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%), and the rotary hearth furnace 100 recovers. The iron content in the zinc oxide is y (mass%), the scattering rate of iron contained in the briquette 22 (= iron contained in the electric furnace dust) is φ, and the zinc oxide contained in the electric furnace dust is recovered. Assuming that the entire amount is recovered at 40, the following relationship is established. Here, the iron scattering rate φ is the ratio of iron (T.Fe) mixed in the zinc-containing substance to the iron (T.Fe) contained in the electric furnace dust.

y = B ・ x ・ φ / (B ・ z + B ・ x ・ φ)
= X ・ φ / (z + x ・ 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 = 8% by mass, the iron scattering rate φ is calculated as follows using the above equation. To. Here, as x and z, 40% by mass and 25% by mass are used as the iron content and the zinc oxide content in the electric furnace dust, respectively.

8% by mass = [40% by mass x φ / (25% by mass + 40% by mass x φ)] x 100
φ = 2 / 36.8 × 100 ≒ 0.05 = 5%

From the above relational expression, when recovering zinc-containing substances from exhaust gas, if the scattering rate φ of iron contained in the electric furnace dust (bricket 22) is set to 5% or less, the iron concentration is equal to or less than that of zinc ore. The inclusions can be recovered. The scattering rate of iron contained in the briquette 22 may be 4% or less, and may be 3% or less.

The flow velocity of the exhaust gas in the rising portion 31 of the exhaust gas pipe 30 may be maintained at, for example, 4.5 m / sec or more, or 6 m / sec or more. If the flow velocity of the exhaust gas is maintained at a high level in this way, the recovery rate of the zinc-containing material can be improved when the zinc-containing material is recovered from the exhaust gas. On the other hand, when the flow velocity of the exhaust gas becomes excessive, the mixing 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 gas pipe 30 may be less than 9 m / sec.

Next, one embodiment of the method of using the rotary hearth furnace will be described below by taking the case where the rotary hearth furnace 100 is used as an example. The above description of the rotary hearth furnace 100 can also be applied to the following usage methods. Further, the following description of the usage method can be applied to the above-mentioned rotary hearth furnace 100.

The method of use of this example is an introduction step of introducing a briquette 22 containing iron oxide and a carbonaceous material on the rotary hearth 12, and heating the briquette 22 in the furnace space 10 while rotating the rotary hearth 12 to oxidize. A heating step for reducing iron, a discharge step for discharging the exhaust gas generated in the heating step from the furnace space 10 through the exhaust gas pipe 30, and a derivation step for deriving the reduced iron-containing material from above the rotary hearth 12. It has a recovery step of recovering the zinc-containing material from the exhaust gas discharged through the exhaust gas pipe 30.

The introduction step may be performed by the introduction unit 21 of FIG. The briquette 22 may contain dust containing iron oxide, a charcoal material such as coal, and a binder. In the introduction step, the briquette 22 is continuously introduced onto the rotary hearth 12. Even if there is a molding step of molding a kneaded product obtained by kneading dust containing iron oxide and zinc oxide, a carbonaceous material and a binder with a double roll molding machine to obtain a briquette 22 before the introduction step. Good.

In the heating step, the briquette 22 is heated by the radiant heat from the burner 14. As a result, the redox reaction represented by the above reaction formula proceeds. As the reaction progresses, voids are formed in the briquette 22, and at least a part of the briquette 22 is pulverized. A part of the pulverized material may flow into the exhaust gas pipe 30 from the furnace space 10 along with the exhaust gas in the discharge process. However, since the furnace space 10 of the rotary hearth furnace 100 used in this example has an H / W of 0.4 or more, the iron content flowing into the exhaust gas pipe 30 from the furnace space 10 can be sufficiently reduced. .. Therefore, the loss of reduced iron is reduced, and the yield of reduced iron can be increased. In addition, it is possible to suppress the mixing of iron into the zinc-containing material recovered in the recovery step, and to produce a zinc-containing material with reduced impurities.

In the discharge step, the exhaust gas generated in the heating step is discharged to the downstream side of the exhaust gas pipe 30 via the exhaust gas pipe 30 connected to the ceiling wall 11a of the furnace body 11. The flow velocity of the exhaust gas in the rising portion 31 of the exhaust gas pipe 30 may be maintained within the above range. At this time, the L / D may be 6.5 or more. This makes it possible to improve the recovery rate of the zinc-containing material recovered in the recovery step and reduce the mixing of iron into the zinc-containing material.

In the derivation step, the reduced iron-containing material is derived from above the rotary hearth 12. The metallization rate of iron in the reduced iron-containing material may be, for example, 70% or more. The derived reduced iron-containing material may be used as a raw material for an electric furnace or the like after being cooled by the cooling unit 62.

In the recovery step, the zinc-containing material is recovered using, for example, a recovery unit 40 having a bug filter. By increasing the flow velocity of the exhaust gas in the rising portion 31 in the discharge process, the recovery rate of the zinc-containing material can be increased. The zinc recovery rate may be 70% or more, and may be 80% or more. The zinc recovery rate is the ratio of the amount of zinc contained in the zinc-containing material recovered in the recovery step (metal zinc equivalent) to the amount of zinc contained in the briquette 22 (metal zinc equivalent).

According to the above-mentioned usage method, the scattering of iron to the outside of the furnace space 10 can be suppressed, and the iron can be sufficiently taken into the reduced iron-containing material obtained in the derivation step and recovered. Therefore, the reduced iron-containing material can be produced with a high yield. In addition, the zinc content contained in the briquette can be sufficiently incorporated into the zinc-containing material recovered in the recovery step and recovered. Further, the iron content mixed in the zinc-containing material can be reduced, and the zinc purity in the zinc-containing material can be sufficiently increased. In this method of use, two products, a reduced iron-containing product and a zinc-containing product, were produced as manufactured products, but in another example, the zinc-containing product was not recovered in the recovery step, and the reduced iron-containing product was produced as a manufactured product. Only may be manufactured. In this case, the dust used to prepare the briquette does not have to contain zinc oxide. In yet another example, only the zinc-containing product may be produced as a product.

One embodiment of the method for producing a reduced iron-containing material is a reduced iron-containing material containing reduced iron by heating a briquette 22 containing iron oxide and a carbonaceous material using a rotary hearth furnace 100 and reducing iron oxide. Has a step of obtaining. Since the rotary hearth furnace 100 is used in this manufacturing method, it is possible to suppress the scattering of iron from the furnace space 10. Therefore, the reduced iron-containing material can be produced with a high yield. The scattering rate of iron contained in the briquette 22 may be, for example, 5% or less, or 4% or less. The reduced iron-containing material may contain iron oxide. The metallization rate of iron in the reduced iron-containing material may be, for example, 70% or more. The above-mentioned description of the rotary hearth furnace 100 and its usage can be applied to the method for producing the reduced iron-containing material of the present embodiment.

In one embodiment of the method for producing a zinc-containing material, an exhaust gas pipe is used to obtain a zinc-containing material contained in an exhaust gas obtained by heating a briquette 22 containing iron oxide, zinc oxide and a charcoal material using a rotary hearth furnace 100. It has a step of collecting by the collecting unit 40 on the downstream side of 30. Since the rotary hearth furnace 100 is used in this manufacturing method, it is possible to suppress the scattering of iron from the furnace space 10. Therefore, it is possible to produce a zinc-containing product in which iron content is suppressed.

The metallic zinc that has been reduced when scattered in the furnace space 10 is oxidized by oxygen in the exhaust gas and cooled by the gas cooling unit 35 provided between the recovery unit 40 and the exhaust gas pipe 30. The content of iron and the iron compound in the zinc-containing material may be 8% by mass or less, 3% by mass or less, and 1% by mass or less in terms of iron. The above-mentioned description of the rotary hearth furnace 100 and its usage can be applied to the method for producing the zinc-containing material of the present embodiment.

Although some embodiments of the present disclosure have been described above, the present disclosure is not limited to the above-described embodiments. For example, in the rotary hearth furnace 100 described above, the rising portion 31 of the exhaust gas pipe 30 is connected to the horizontal portion 32, but the present invention is not limited to this. For example, in the modified example, the ascending portion 31 may be in an inverted U shape in connection with the descending portion descending from the highest reaching point instead of the horizontal portion 32. Even if there is a second or subsequent rising portion that rises along the flow of the exhaust gas on the downstream side of the horizontal portion 32 (or the descending portion), the length of this portion is not included in the above L. This is because even if the iron content or the like falls in the second and subsequent ascending portions, it is not always possible to return to the furnace space 10.

Further, when the zinc content in the briquette is low, it is not necessary to recover the zinc-containing material in the rotary hearth furnace and its usage method. In this case, in the rotary hearth furnace, only the reduced iron-containing material may be produced as a produced product. Further, the burner 14 may be provided not on both inner and outer side surfaces of the furnace body 11, but on only one of the side surfaces.

The contents of the present disclosure will be described in more detail with reference to the following examples and comparative examples, but the present disclosure is not limited to the following examples.

(Example 1, Comparative Example 1)
As shown in Table 1, a plurality of types of rotary hearth furnaces having different widths W and heights H were prepared. Each rotary hearth furnace had a structure as shown in FIGS. 1 and 2. Briquettes were made using electric furnace dust, pulverized coal and binder. This briquette was introduced into a rotary hearth furnace to produce a reduced iron-containing substance and a zinc-containing substance. When each rotary hearth furnace was used, the iron content in the zinc-containing material recovered by the bag filter (recovery unit 40) provided on the downstream side of the exhaust gas pipe 30 was analyzed. The iron content is the total iron content (T.Fe) including not only metallic iron but also iron contained in iron oxide and the like. This content was determined by chemical analysis. The results are as shown in Table 1 and FIG.

As shown in Table 1 and FIG. 3, it was confirmed that the iron content in the zinc-containing material recovered by the bag filter was sufficiently lowered 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 different cross-sectional areas inside the exhaust gas pipe 30 having a cylindrical shape were prepared. Each rotary hearth furnace had a structure as shown in FIGS. 1 and 2. Briquettes were made using electric furnace dust, pulverized coal and binder. This briquette was introduced into a rotary hearth furnace to produce a reduced iron-containing substance and a zinc-containing substance. The zinc recovery rate when each rotary hearth furnace was used was calculated. As the briquette, one prepared by using electric furnace dust, pulverized coal, and a binder was used. The zinc recovery rate is the ratio of the amount of zinc contained in the zinc-containing material recovered by the bag filter (recovery unit 40) to the amount of zinc contained in the briquette (metal zinc equivalent). The results are as shown in Table 2 and FIG.

As shown in Table 2 and FIG. 4, it was confirmed that the zinc recovery rate can be increased by increasing the flow velocity of the exhaust gas. According to FIG. 4, if the flow velocity of the exhaust gas is maintained at 4.5 m / sec or more, the zinc recovery rate can be 80% or more.

(Example 3)
As shown in Table 3, a plurality of types of rotary hearth furnaces having different inner diameters D of the exhaust gas pipe 30 and length L of the rising portion 31 of the exhaust gas pipe 30 were prepared. Each rotary hearth furnace had a structure as shown in FIGS. 1 and 2. Briquettes were made using electric furnace dust, pulverized coal and binder. This briquette was introduced into a rotary hearth furnace to produce a reduced iron-containing substance and a zinc-containing substance. The iron scattering rate φ when each rotary hearth furnace was used was determined. The iron scattering rate φ is the 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 as shown in Table 3 and FIG. Table 3 shows the calculated values of the flow velocity V of the exhaust gas in the exhaust gas pipe 30 and V ² × (L / D), which is an element constituting the pipe friction coefficient. FIG. 5 is a ^{log-log graph in which the horizontal axis is V 2} × (L / D) and the vertical axis is the iron scattering rate.

As shown in Table 3 and FIG. 5, it was confirmed that the iron scattering rate φ increases as ^{V 2 × (L / D), which is an element constituting the pipe friction coefficient, increases.} This is because the iron that has once flowed from the furnace space 10 into the rising portion 31 of the exhaust gas pipe 30 returns to the furnace space 10 due to the influence of friction with the inner wall of the rising portion 31, and is recovered as a reduced iron-containing substance. It shows that. ^{As shown in FIG. 5, the value of V 2} × (L / D) when the iron scattering rate φ = 5% was 132. That is, when a briquette containing electric furnace dust is used, if the ^{operating conditions are set so that the value of V 2} × (L / D) is 132 (m ² / sec ² ) or more, the zinc content is recovered. It is presumed that the iron content mixed in the material can be sufficiently reduced.

From the results of Table 2 and FIG. 4 of Example 2, it is necessary to maintain the flow velocity V of the exhaust gas at 4.5 m / sec or more in order to increase the zinc recovery rate. In order to sufficiently reduce the iron content mixed in the recovered zinc-containing material, in the relational expression of ^{V 2} × (L / D) ≧ 132 (m ² / sec ^{2) derived from Table 3 and FIG. 5, V} Substituting = 4.5 m / sec, L / D ≧ 6.5. Therefore, it can be said that the L / D is preferably 6.5 or more.

10 ... Furnace space, 11 ... Furnace body, 11a ... Ceiling wall, 11b ... Side wall, 11c ... Ceiling surface, 12 ... Rotating hearth, 14 ... Burner, 16 ... Running wheels, 21 ... Introduction, 22 ... Bricket, 24 ... transport section, 30 ... exhaust gas pipe, 31 ... rising section, 32 ... horizontal section, 35 ... gas cooling section, 40 ... recovery section, 50 ... chimney, 60 ... lead-out section, 62 ... cooling section, 100 ... rotary hearth furnace , H ... height, W ... width, L ... length, D ... inner diameter.

As shown in Table 3 and Figure 5, the scattering rate of the iron φ it is small Kunar was confirmed when V ² × is an element constituting the pipe friction coefficient (L / D) is increased. This is because the iron that has once flowed from the furnace space 10 into the rising portion 31 of the exhaust gas pipe 30 returns to the furnace space 10 due to the influence of friction with the inner wall of the rising portion 31, and is recovered as a reduced iron-containing substance. It shows that. ^{As shown in FIG. 5, the value of V 2} × (L / D) when the iron scattering rate φ = 5% was 132. That is, when a briquette containing electric furnace dust is used, if the ^{operating conditions are set so that the value of V 2} × (L / D) is 132 (m ² / sec ² ) or more, the zinc content is recovered. It is presumed that the iron content mixed in the material can be sufficiently reduced.

Claims (11)

A rotary hearth furnace including an annular furnace body having a burner, a rotary hearth rotating inside the furnace body, and an exhaust gas pipe connected to the ceiling wall of the furnace body.
A rotary hearth furnace having a H / W of 0.4 or more, where W and H are the widths and heights of the space inside the furnace composed of the rotary hearth and the furnace body, respectively. The rotary hearth furnace according to claim 1, wherein the L / D is 6.5 or more when the length of the rising portion of the exhaust gas pipe is L and the inner diameter of the rising portion is D. The rotary hearth furnace according to claim 1 or 2, wherein the flow velocity of the exhaust gas in the rising portion of the exhaust gas pipe is 4.5 m / sec or more. An introduction part that introduces a briquette containing electric furnace dust and charcoal material onto the rotary hearth,
A derivation unit for deriving the reduced iron-containing material from above the rotary hearth,
The rotary hearth furnace according to any one of claims 1 to 3, further comprising a recovery unit for recovering zinc-containing substances contained in the exhaust gas on the downstream side of the exhaust gas pipe. A method for producing a reduced iron-containing material using the rotary hearth furnace according to any one of claims 1 to 4.
A method for producing a reduced iron-containing material, which comprises a step of heating a briquette containing iron oxide and a carbonaceous material and reducing the iron oxide to obtain a reduced iron-containing material containing reduced iron. The method for producing a reduced iron-containing material according to claim 5, wherein the scattering rate of iron contained in the briquette is 5% or less. A method for producing a zinc-containing material using the rotary hearth furnace according to any one of claims 1 to 4.
A method for producing a zinc-containing material, which comprises a step of recovering the zinc-containing material contained in the exhaust gas obtained by heating a briquette containing iron oxide, zinc oxide and a charcoal material. The method for producing a zinc-containing product according to claim 7, wherein the zinc recovery rate is 70% or more. The method for producing a zinc-containing product according to claim 7 or 8, wherein the iron content in the zinc-containing product is 8% by mass or less. A method of using a rotary hearth furnace including an annular furnace body having a burner, a rotary hearth rotating inside the furnace body, and an exhaust gas pipe connected to the ceiling wall of the furnace body.
An introduction step of introducing a briquette containing iron oxide and a charcoal material on the rotary hearth, and
A heating step of heating the briquette in a furnace space composed of a rotary hearth and a furnace body while rotating the rotary hearth to reduce the iron oxide.
An exhaust step of discharging the exhaust gas generated in the heating step from the furnace space through the exhaust gas pipe, and a discharge step.
It has a derivation step of deriving the reduced iron-containing material from the top of the rotary hearth.
A method of using a rotary hearth furnace in which H / W is 0.4 or more when the width and height of the furnace space are W and H, respectively. It has a recovery process for recovering zinc-containing substances from the exhaust gas that has flowed through the exhaust gas pipe.
The method for using a rotary hearth furnace according to claim 10, wherein in the discharge step, the flow velocity of the exhaust gas in the portion extending above the exhaust gas pipe is maintained at 4.5 m / sec or more.

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