JP2002302710A - Method for operating rotary hearth furnace, method for laying agglomerate onto rotary furnace hearth and facility for supplying raw material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To surpress wear and damage of a carrying-out means of an agglomerate and, to improve operating rate of a reducing operation by easily performing the removal of deposited layer formed on the hearth surface of a rotary furnace. SOLUTION: The agglomerate 3 and carbonaceous material 4 are mixedly laid on the rotary furnace hearth 10 in the rotary hearth furnace 1 for reducing the agglomerate containing iron oxide raw material, and in the driving process of the rotary hearth furnace, this carbonaceous material is mixed in the deposited layer formed on the rotary furnace hearth to form the deposited layer easily removable even with the carry-out means such as a screw conveyor 11.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for laying agglomerates on a rotary hearth of a rotary bed furnace for reducing agglomerates containing an iron oxide raw material. The present invention relates to a method of laying an agglomerate that facilitates removal of a sedimentary layer formed on a rotary hearth surface due to accumulation of powder resulting from a product or the like.

[0002] The present invention also relates to a facility for supplying raw materials such as agglomerates and carbon materials used in the production of reduced iron by a rotary bed furnace.

[0003]

2. Description of the Related Art As a method for producing reduced iron by treating dust, scale, sludge, etc., including fine iron ore and iron generated in an ironworks, etc., a heated hearth furnace in which a hearth rotates horizontally is used. Attention has been paid to a method using a "rotating hearth furnace"). In this method, in general, an agglomerate obtained by mixing and molding a powdered iron oxide raw material and a powdery reducing agent is spread over a rotary hearth surface of a rotary hearth furnace, and the agglomerate is moved in the hearth furnace. And reducing by heating to obtain reduced iron.

FIG. 9 shows an example of a process for producing reduced iron using a rotary bed furnace. An example of the production of reduced iron using a rotary hearth furnace will be described with reference to this process chart. As shown in the figure, fine iron oxide ore, dust, scale, sludge, dust generated in the process of manufacturing stainless steel, powdered iron oxide raw materials such as sludge, and pulverized coal are mixed, and the moisture is further reduced by a kneader. Add and mix. This mixed raw material is agglomerated by a granulator such as a pelletizer or a double roll compressor. Usually, after this, the agglomerate is dried by a dryer in order to adjust the water content. After drying, the agglomerates are transferred to the raw material charging section of the rotary bed furnace and charged into the furnace. The agglomerate is sent to a rotary hearth furnace by a belt conveyor or the like, and is charged therefrom using a charging chute or the like so as to be widely dispersed on the rotary hearth, and is leveled by a leveler or the like. The iron oxide in the agglomerate is reduced at a high temperature to make solid metallic iron during one rotation with the movement of the rotary hearth. The obtained metallic iron is taken out from the discharge part.

[0005] In a rotary bed furnace, fuel gas and air are fed into the furnace and burned, so that it is about 900-1400.
The furnace temperature of ° C is secured. The above-mentioned agglomerate is spread on the hearth of this rotary bed furnace with a thin thickness of about 10 to 20 mm,
The temperature is raised to 900 ° C or higher mainly by a gas burner or the like from the furnace inner wall. The agglomerates reduced by a scraping device such as a screw conveyor (also called a screw feeder) are discharged from the section.

[0006]

The agglomerates to be charged into the rotary hearth furnace include pellets, briquettes,
Extrusion molding and cutting may be mentioned. These agglomerates break during the agglomeration before being transferred to the rotary hearth furnace, when laying the agglomerates on the rotary hearth floor, or during the heating process. Sometimes.
When the agglomerate cracks, powder is generated, and powder containing iron falls and accumulates on the rotary hearth surface. Further, it is practically difficult to remove 100% of the powder adhering to the surface of the agglomerate before charging it into the rotary bed furnace. It falls on the floor and causes powder to accumulate.

[0007] The powder containing iron accumulated in the rotary hearth is heated in the furnace and gradually fused and solidified (hereinafter, the solidified sedimentary layer is simply referred to as “sedimentary layer”). ). In particular, when a screw conveyor or the like is used as a means for carrying out the agglomerates, the solidified layer is likely to be formed by being rolled at the wings or the like.

[0008] The formation of a deposited layer on the rotary hearth surface as described above causes the following problems in the operation of the rotary hearth furnace. For example, when the gap between the furnace floor and the material inlet is narrow, the inlet may be damaged due to the thicker deposited layer. Further, the blades of the screw conveyor or the scraper provided at the outlet of the agglomerate may be worn or even damaged.

Therefore, there is a need to remove the deposited layer. In order to remove the sedimentary layer, it is conceivable to periodically stop the reduction operation in the rotary bed furnace and peel off and remove the sedimentary layer. However, frequently stopping the reduction operation only for removing the sedimentary layer is not preferable in terms of the operation rate.

[0010] As a method of removing the deposited layer, a method of providing a rotary bed furnace with a crusher for crushing the deposited layer has been disclosed (Japanese Patent Application Laid-Open No. 2000-109913). However, providing a separate crusher is inconvenient in that the mechanism of the rotary hearth furnace is complicated and equipment costs are increased.

SUMMARY OF THE INVENTION The present invention has been made in view of the above, and it is possible to easily remove a deposited layer formed on a rotary hearth surface, thereby suppressing abrasion and damage of an agglomerate discharge means. In addition, the aim is to improve the operation rate of the reduction operation.

[0012]

Means for Solving the Problems The present inventors have conducted intensive research on a method for easily removing a deposited layer.
This led to the idea that the sedimentary layer itself should be formed in such a way that it could be easily crushed and peeled off. For that purpose, it is preferable that the carbonaceous material be contained in the sedimentary layer formed mainly of iron. And completed the present invention.

That is, the present invention is as follows. (1) A method of operating a rotary hearth furnace in which a carbonaceous material is mixed into a sedimentary layer formed on a rotary hearth during the operation of the rotary hearth furnace for reducing agglomerates containing iron oxide raw materials. (2) The agglomerate is laid on a rotary hearth of a rotary hearth furnace for reducing agglomerates containing iron oxide raw materials, and a carbonaceous material is charged into the rotary hearth to rotate during the operation of the rotary hearth furnace. A method of laying agglomerates on a rotary hearth, wherein the carbonaceous material is mixed in a sedimentary layer formed on the hearth. (3) A mixture of the agglomerate and the carbon material is laid on a rotary hearth of a rotary hearth furnace for reducing agglomerates containing an iron oxide raw material, and the rotary hearth is operated during the operation of the rotary hearth furnace. A method of laying agglomerates on a rotary hearth, wherein the carbonaceous material is mixed in a sedimentary layer formed in the furnace. (4) The method for laying agglomerates on a rotary hearth according to (2) or (3), wherein a carbonaceous material charging means is provided, and the carbonaceous materials are mixed with the agglomerate in a rotary hearth furnace. (5) The method according to any one of (2) to (4), wherein the means for discharging the agglomerate after the reduction treatment provided in the rotary bed furnace is a scraping device such as a screw conveyor, a scraper, or a pusher. Method of laying agglomerates on rotary hearth. (6) The carbon material according to any one of (2) to (5), wherein the carbon material is at least one selected from the group consisting of coal, coke, char, oil coke, waste plastic, and waste tire chips. Method of laying agglomerates on the rotary hearth. (7) The lump on the rotary hearth according to any of (2) to (6), wherein the carbonaceous material mixed with the agglomerate has a weight percentage of 20% or less with respect to the agglomerate. How to lay a product. (8) Equipment for supplying one or both of the agglomerate and the carbonaceous material to a hearth of a rotary bed furnace for reducing agglomerates containing an iron oxide raw material and producing reduced iron, Agglomerate supply means for supplying the agglomerate, carbon material supply means for supplying a carbon material, agglomerate supplied from the agglomerate supply means and charcoal supplied from the carbon material supply means Raw material supply equipment for producing reduced iron using a rotary bed furnace, comprising: conveying means for transferring one or both of the materials to a rotary bed furnace. (9) A facility for supplying carbonaceous material to a hearth of a rotary bed furnace for reducing agglomerates including an iron oxide raw material and producing reduced iron,
A carbon material supply facility for producing reduced iron by a rotary bed furnace, comprising: a carbon material supply means for supplying a carbon material; and a transport means for transporting the carbon material supplied from the carbon material supply means to a rotary bed furnace.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION In a method for producing reduced iron by reducing agglomerates containing an iron oxide raw material using a rotary bed furnace, a deposited layer is formed as follows in the operation process of the rotary bed furnace. To go. First, powder generated by cracking of the agglomerate, powder adhering to the surface of the agglomerate, and the like fall and accumulate on the rotary hearth. The accumulated powder is heated in a furnace and rolled by a screw conveyor wing or the like, which is a means for discharging agglomerates, to form a deposited layer in which the powder is fused and solidified, and gradually becomes thicker. Go. According to the present invention, the deposited layer formed on the hearth surface is easily removed. Therefore, in the present invention,
A carbon material is mixed into the sedimentary layer so that the sedimentary layer can be easily crushed or separated and removed by a carrying-out means such as a screw conveyor for carrying out the agglomerate after the reduction treatment. Then, as means for mixing the carbon material into the sedimentary layer, agglomerates are laid and the carbon material is charged into the rotary hearth. Hereinafter, embodiments of the present invention will be described in more detail.

The rotary bed furnace used in the present invention is already known as a facility used for reducing agglomerates containing iron oxide, and in the present invention, the known rotary bed furnace may be used. it can. FIG. 2 illustrates a rotary hearth furnace.

The agglomerates refer to pellets, briquettes, extruded and cut molded articles, and granules / agglomerates such as aggregates having a controlled particle size. These can be those generally used when reducing iron oxide using a rotary hearth, and can be produced by a general method of forming such agglomerates. The size of the agglomerate may be appropriately adjusted depending on the conditions of reduction using a rotary bed furnace, etc., but preferably, the particle size of one agglomerate is about 8
２５25 mm.

The components to be added to the agglomerate are a powdery iron oxide raw material, a reducing agent, and, if necessary, water and a binder other than water.

As the iron oxide raw material, in addition to powdery iron ore, various dusts, sludges, scales, etc., containing iron generated in ironworks can be used. It is also possible to use dust, scale, sludge, etc. generated in the process of manufacturing stainless steel. In order to form an agglomerate, usually, a powdered iron oxide raw material is used. Also,
As the reducing agent, coal, coke, char, oil coke, waste plastic, waste tire, and the like can be used, and it is preferable that these reducing agents are also powdered and mixed with the powdery iron oxide raw material.

The iron oxide raw material and the reducing agent are mixed and molded. At this time, if necessary, water,
Starch, tar, molasses, organic resin, cement, slag,
Bentonite, quicklime, lightly burned dolomite, slaked lime and the like are added. The agglomerate formed in accordance with a usual method may be dried in order to adjust the moisture.

In the production of reduced iron, agglomerates are laid on a rotary hearth surface of a rotary hearth furnace and reduced. In the present invention, the carbonaceous material may be mixed into the sedimentary layer formed during the reduction operation of the agglomerate. In order to mix the carbonaceous material into the sedimentary layer, the carbonaceous material is put into a rotary bed furnace. In one embodiment of the present invention, the agglomerate and the carbonaceous material are mixed and both are simultaneously spread and formed. A carbon material is interposed in the agglomerate laying layer. By interposing carbonaceous material in the agglomerate laying layer, carbonaceous material is mixed and accumulated on the hearth with powder containing iron that causes the sedimentary layer during the rotating operation, and the carbonaceous material is mixed A deposited layer is formed (FIG. 4). Alternatively, as another embodiment of the present invention, after the agglomerates are spread in advance, the carbonaceous material may be charged into the furnace. That is, a means for charging a carbon material may be provided separately from the charging means for the agglomerate, and the agglomerate and the carbon material may be mixed in the furnace. In order to put the carbon material after the agglomerate is laid in advance, for example, use a means such as providing a carbon material inlet on the ceiling or side wall of the rotary bed furnace and dropping it onto the agglomerate from there Can be.
The number of carbon material inlets may be one or more.

In order to mix and agglomerate the agglomerate and the carbonaceous material, as described above, a method of mixing the agglomerate and the carbonaceous material and simultaneously laying them on a rotary hearth, or After laying, there is a method of putting carbon material. In other words, the carbonaceous material may be mixed with the agglomerate at any one or more of the "carbonaceous materials I to III" as shown in FIG.

The carbonaceous material interposed in the agglomerate laying layer may be any material as long as it mixes with the sedimentary layer and forms a crack origin that facilitates crushing and peeling of the sedimentary layer when the sedimentary layer is removed. As the carbon material interposed in the laying layer in the present invention, preferably, coal,
Examples include coke, char, oil coke, waste plastic, waste tire chips, and the like, and one or more of these may be used. When a carbon material having a high volatile content such as waste plastic or tire is added as a carbon material, a combustible gas is generated, so that the combustion gas flow rate in the furnace can be reduced.

The upper limit of the amount of the carbonaceous material laid on the rotary hearth mixed with the agglomerate is preferably 20% by weight or less, more preferably 5% by weight or less based on the agglomerate. is there. When the amount is equal to or less than the upper limit, the production of reduced iron is hardly hindered.

On the other hand, the lower limit of the amount of the carbonaceous material laid on the rotary hearth mixed with the agglomerate is preferably 0.01% by weight, particularly preferably 1% by weight, based on the agglomerate. When the thickness is equal to or more than the lower limit, it is suitable for forming a deposited layer which can be easily removed.

The size of the carbon material mixed in the sedimentary layer is preferably about 200 mm or less, particularly preferably about 5 mm or less. A material having such a size becomes a weak point when removing the deposited layer by a carrying-out means such as a screw conveyor or the like, and suitably acts for removing the deposited layer.

FIG. 3 schematically shows the state of the agglomerate laying layer in which coal is interposed (in FIG. 3, the particle size of the agglomerate is 1 to 2).
It shows a state in which a layer is formed with a thickness about twice as large.)
As illustrated in FIG. 3, in the case of coal or the like, it is not necessary to strictly uniform the particle size, and a material having substantially the same particle size as the agglomerate is laid between the inclusions. Or part of the pulverized coal may be grounded to the hearth.

The method of laying the agglomerate or the like may be performed according to a method generally used for laying the agglomerate as the iron oxide raw material in the rotary bed furnace. It is preferable to employ a method in which a powder that causes the formation of a deposited layer is less likely to be generated due to cracking of the product, since the formation of the deposited layer itself is suppressed in the first place. The carbonaceous material may be charged with a mixture previously mixed with the agglomerate, or may be laid on the rotary hearth together with the agglomerate at the time of charging.

The agglomerates and carbonaceous materials laid so as to be mixed on the rotary hearth can be efficiently supplied by the following raw material supply equipment. That is, an agglomerate supply means for supplying the agglomerate, a carbon material supply means for supplying a carbon material,
A conveying unit for conveying one or both of the agglomerate supplied from the agglomerate supply unit and the carbon material supplied from the carbon material supply unit to a rotary bed furnace, The raw material supply equipment for the production of reduced iron by the above method can be suitably used. Raw material supply facilities are raw materials for reduced iron,
Equipment for supplying materials required for the production of reduced iron.

FIG. 8 shows a specific example. The raw material supply equipment illustrated in FIG. 8 includes a pellet hopper 14 as agglomerate supply means and a coal hopper 15 as a carbon material supply means.
And a pellet conveyor 17 and a coal conveyor 16 as transport means. Pellet hopper 14
The pellet cutting device 141 in the pellet sending section.
Is provided. The coal hopper 15 is provided with a coal cutting device 151 at a coal delivery section.

The agglomerates accumulated in the pellet hopper 14 are transferred to a pellet conveyer 17 by a predetermined amount of pellets via a pellet cutting device 141. On the other hand, a predetermined amount of coal is carried out of the coal hopper 15 onto the coal conveyor 16 via the coal cutting device 151.
The coal on the coal conveyor 16 is conveyed on the conveyor and mixed with the agglomerates conveyed by the pellet conveyor 17. The agglomerate charged with coal is further conveyed by a pellet conveyor 17 and charged into a rotary bed furnace (not shown) which is a reduction furnace.

By separately providing the agglomerate supply means and the carbonaceous material supply means, the mixing amount of the carbonaceous material with the agglomerate serving as the iron oxide raw material can be easily adjusted. The method for laying agglomerates according to the invention can be carried out smoothly. If necessary, only one of the agglomerate and the carbonaceous material can be transferred to the rotary bed furnace.

In the raw material supply equipment of the present invention, there is no particular limitation on the arrangement positions of the agglomerate supply means and the carbon material supply means. For example, in FIG. 8, a pellet hopper or the like is arranged so as to add coal to the pellets conveyed on the pellet conveyor 17. On the contrary, the arrangement is such that the pellets are added on a coal conveyor conveying coal. Is also good. Further, in FIG. 8, after the coal is once supplied from the coal hopper 15 to the coal conveyor 16, the coal conveyed by the coal conveyor is added to the agglomerates on the pellet conveyor 17, but directly from the coal hopper. Coal may be supplied to the pellet conveyor. Further, a coal hopper may be provided immediately before the charging port of the rotary bed furnace so that coal and agglomerates are mixed when the coal and the agglomerate are charged into the charging port.
Further, as described above, the pellet hopper 14 may not be provided as the agglomerate supply means, and the carbonaceous material supply means may be provided in the process of transporting the manufactured agglomerate to supply the carbonaceous material.

In equipment in which the agglomerate manufacturing equipment and the rotary bed furnace are connected, a dryer for drying the agglomerate may be provided before the rotary bed furnace in the process of transporting the agglomerate. is there. In the case where such a dryer is provided, if the carbon material such as coal is treated by the dryer, it may be ignited. Desirably after passing through the dryer ("Charcoal material II" in Fig. 1)
Corresponds to the position indicated by. ). Alternatively, a method in which the coal hopper 15 and the coal conveyor 16 are installed on the furnace and charged from the furnace by forming a seal structure is also within the scope of the present invention (corresponding to the position indicated by "Carbon material III" in FIG. 1). Do).

[0034] The agglomerate or the like charged into the rotary hearth is usually laid so that the surface is as flat as possible to form an agglomerate laying layer. At this time, a leveler or the like may be used. In a rotary hearth furnace, the hearth rotates and moves, so the thickness of the agglomerate laying layer can be adjusted by adjusting the amount of agglomerate charged and the rotation speed of the hearth. The charge of the agglomerate is expressed, for example, as the weight of the agglomerate per unit time. Conditions such as the charged amount of agglomerates and the rotation speed can be appropriately determined.

As described above, the agglomerate and the carbonaceous material are mixed and laid, and reduced iron can be produced according to a normal reduced iron production method. The reduced agglomerate is a screw conveyor,
It is carried out of the furnace by carrying out means such as a scraper and a pusher (extrusion device).

[0036] If the means for carrying out the agglomerate after the reduction treatment provided in the rotary bed furnace is a scraping device such as a screw conveyor or a scraper, the powder accumulated on the rotary bed furnace is substantially rolled. And tends to form a strong deposited layer. The present invention is particularly suitable for producing reduced iron in a rotary bed furnace equipped with such a scraping device.

When the sedimentary layer is removed by a scraping device such as a screw conveyor or a scraper, the height of the wing is adjusted so that the wing such as a screw bites into the deposition tank.
It can be easily performed by adjusting the number of revolutions of the screw and the like.

Since the sedimentary layer formed by mixing carbonaceous material during the reduction treatment is more easily crushed or separated than that in which no carbonaceous material is mixed, the reduced agglomerate is discharged from the rotary bed furnace. It can also be easily removed by a scraping device such as a screw conveyor or a scraper which is generally used. If the scraping device attempts to remove the sedimentary layer containing no carbon material, the wings and the like are severely worn, the possibility of damage is increased, and the load on the power is increased.

FIG. 5 exemplifies a state in which a sedimentary layer is crushed and separated when a screw conveyor is used as a scraping device. As shown in FIG. 5, when carbon material is contained in the sedimentary layer, when the screw pressure is applied, the carbonaceous material part becomes a weak point and serves as a crack starting point, and the sedimentary layer is easily crushed and separated. Become.

The laying method of the present invention is based on the idea of how to easily remove the formed sedimentary layer. By combining with the method of suppressing
It functions more effectively as a countermeasure for sedimentary layers in a rotary hearth furnace.

One example of a method for suppressing the formation of a deposited layer itself is described herein (“the method for suppressing the formation of a deposited layer of the present invention” in this specification)
). The layer of agglomerates and the like laid by one rotation of the hearth is counted as one stage.

Usually, the agglomerate is charged and discharged from the furnace when the rotary hearth makes one rotation. In the method for suppressing the formation of a deposited layer of the present invention, reduction is performed while first forming a plurality of laid layers by rotating the hearth a plurality of times, and in each subsequent round, a larger amount of agglomerate than the charged amount is taken out of the furnace. Unloading, continuing the round, unloading the reduced agglomerate at the bottom, repeats the same operation again from the beginning.

As a specific example, from the start of the operation, the agglomerate is not discharged for 4 rotations of the hearth, and the charging of the agglomerate is continued. A laying layer is formed in which the agglomerates being processed are stacked in four stages.
From the fifth rotation, while maintaining the same charge amount, two stages (that is, equivalent to twice the charge amount) are carried out of the floor furnace by a screw conveyor or the like. Then, at the end of the fifth rotation, three laying layers remain on the hearth. When two rounds of unloading are continued and each round is repeated, at the end of eight rotations, the agglomerate that was initially at the bottom is unloaded. Thereafter, the same operation is repeated.

According to this method, it is possible to increase the time during which the hearth surface is covered with the plural layers of the agglomerate laying layer during the reduction operation. By being covered with a plurality of steps, it is possible to suppress the powder that causes the sedimentary layer from dropping to the hearth surface and suppress the formation of the sedimentary layer. That is,
The agglomerate laying layer is used as a pseudo hearth. In addition, when the layer is unloaded, the thickness of the layer is gradually reduced, so that the load, abrasion, damage, and the like of the unloading unit such as a screw conveyor can be reduced.

As described above, according to the laying method of the present invention,
By combining the method for suppressing the formation of a deposited layer of the present invention, various adverse effects due to the deposited layer in a rotary bed furnace can be significantly reduced.

[0046]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to the following examples.

Example 1 (1) Production of Raw Material Pellets Raw material pellets for producing reduced iron were produced according to the process shown in FIG. Table 1 shows the composition of the raw material pellets, and Table 2 shows the chemical composition. Before mixing each component, the particle size was adjusted using a ball mill and water was added in advance using a humidifier. Table 3 shows the adjustment conditions by the ball mill. The pellets were formed using a dish-type granulator to obtain pellets (raw pellets) having a particle size of 8 to 12 mm. The raw pellets were dried in a drier to a water content of 1% or less to obtain raw material pellets to be charged into a rotary bed furnace.

[0048]

[Table 1]

[0049]

[Table 2]

[0050]

[Table 3]

(2) Transport of raw materials and production of reduced iron by rotary bed furnace The above-mentioned raw material pellets were charged into a rotary bed furnace, and the raw material pellets were reduced while rotating the rotary hearth to produce reduced iron. .

The raw material pellets and coal were mixed and transported by using equipment having the structure shown in FIG. Note that the raw material pellets were subjected to a drying treatment by a drier at a stage before being charged into the pellet hopper. That is, in the present embodiment, the carbon material was supplied at the position of "carbon material II" in the process diagram of FIG.

The raw material pellets have a particle size of about 15 mm.
The following coal was previously blended at a ratio of 3% by weight, and the coal was interposed in the laying layer. The raw material pellets containing the coal were laid on the hearth surface along with the rotation of the rotary hearth through the charging inlet, and the surface of the laid layer of the pellets was leveled by a leveler. The loading amount of the pellets was such that the laying layer was added by about 8 to 20 mm (thickness of one or two pellets) by the loading of the pellets. Table 4 shows the specifications of the rotary hearth furnace.
Table 5 shows the conditions for reduction using a rotary hearth furnace.

[0054]

[Table 4]

[0055]

[Table 5]

The pellets reduced according to the operating conditions of the rotary bed furnace were carried out by a screw conveyor, and the pellets were carried out every rotation.

(3) Removal of the sedimentary layer When a sedimentary layer of about 50 mm was formed by the operation of the rotary hearth furnace, the height of the screw of the screw conveyor was adjusted, and the rotational speed of the rotary hearth was adjusted. Was removed. It was confirmed that coal was mixed in the removed sedimentary layer.

<Example 2> The frequency of unloading the reduced pellets, the unloading amount per rotation, and the thickness of the laying layer of the pellets were changed as follows, and other conditions were the same as in Example 1. Production of reduced iron and removal of sedimentary layers were performed.

First, during the four rotations of the hearth, reduction was carried out while stacking and laying the pellets for four rotations without carrying out by the screw conveyor. At the fifth rotation, while maintaining the charge amount unchanged, the height of the screw is adjusted so as to carry out a pellet having a thickness (about 30 to 40 mm) corresponding to the charge amount for two rotations. I scraped it out. At the end of the fifth rotation, pellets having a thickness of three rotations remained on the hearth surface. By carrying out the pellets in this way, at the end of the eight rotations, the pellets were first carried out to the lowermost laid pellet. The above operation was repeated from the ninth rotation.

<Example 3> Production of reduced iron and supply of carbon material were performed in the same manner as in Example 1, and waste plastic was further charged as new carbon material from the furnace through the carbon material inlet 8 shown in FIG. did. The size of the waste plastic put into the furnace is 1
The diameters of 0, 20, and 40 mm were used, and the charging speed was set so as to correspond to 1% of the agglomerate.

<Comparative Example 1> Pellets were laid without blending coal into the raw material pellets, and reduced iron was produced under the same conditions as in Example 1 above, and the deposited layer was further removed. Was.

<Comparison of Deposition Layer Removal Speed> The amount of the deposition layer that can be removed per unit time (deposition layer removal speed) was compared between Example 1 and Comparative Example 1. Specifically, the piled layer formed by laying the pellets on the hearth without mixing the carbonaceous material was scraped by a screw conveyor (Comparative Example 1), and the amount of the removed layer per unit time was deposited. The layer removal rate index “1” was compared with the deposited layer removal rate index in the case of Example 1. FIG. 6 shows the results.

By mixing coal (charcoal) into the sedimentary layer as in Example 1, the sedimentary layer is crushed by a screw.
As shown in FIG. 6, the removal rate of the deposited layer in Example 1 was more than twice as fast as that in Comparative Example, as shown in FIG.

By adding not only coal but also waste plastic to the rotary bed furnace as a carbon material addition (Example 3),
As shown in FIG. 6, the deposition layer removal speed is further improved.

<Comparison of Screw Life> The life of the screw conveyors of Examples 1 and 2 and Comparative Example 1 was compared. Specifically, the comparison was made by assuming that the life of the screw conveyor in Comparative Example 1 was 1. FIG. 7 shows the results.

As shown in FIG. 7, it became clear that the life of the screw was prolonged when the coal (carbon material) was interposed in the laying layer.

By adding not only coal but also waste plastic to the rotary bed furnace as a carbon material addition (Example 3), the screw life is further improved as shown in FIG.

[0068]

According to the present invention, the sedimentary layer formed on the rotary hearth surface can be easily removed, and wear and damage of the agglomerate discharge means such as a screw conveyor can be reduced. Furthermore, the number of times of stopping and performing the reduction operation of the rotary hearth furnace due to the formation of the sedimentary layer can be reduced, the operation rate can be improved, and the amount of combustion gas can be reduced.

In the method for laying agglomerates according to the present invention, the amount of carbonaceous material can be easily adjusted by using the raw material supply equipment of the present invention.

[Brief description of the drawings]

FIG. 1 is a diagram showing a process from formation of agglomerates to charging of the agglomerates into a rotary bed furnace and carrying out reduced iron.

FIG. 2 is a view showing a rotary hearth furnace.

FIG. 3 is a schematic view of an agglomerate laying layer.

FIG. 4 is a schematic diagram showing a state in which powder accumulated on a rotary hearth is rolled by a screw to form a deposited layer, as viewed from an axial direction of a screw conveyor.

FIG. 5 is a diagram showing a state in which the tip of a screw conveyor is cut into a piled layer to break the piled layer.

FIG. 6 is a diagram showing a removal rate of deposits.

FIG. 7 is a view showing a screw life.

FIG. 8 is a diagram showing one embodiment of a raw material supply apparatus for supplying pellets and coal.

FIG. 9 is a diagram illustrating an example of a production process when producing reduced iron using a rotary hearth furnace.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Rotating hearth furnace 10 ... Rotating hearth 11 ... Screw conveyor 12 ... Loading port 13,14 ... Partition wall 101 ... Inner wall 102 ... Outer wall 103 ... Gas burner flame 104: Burner and air introduction device 3: Pellet 4: Carbon material (coal, etc.) 5: Laying layer of agglomerate 6: Mainly iron stored on the hearth surface Powder 7 ・ ・ ・ Deposited layer 8 ・ ・ ・ Carbon material inlet 9 ・ ・ ・ Rotating floor furnace ceiling 14 ・ ・ ・ Pellet hopper 141 ・ ・ ・ Pellet cutting device 15 ・ ・ ・ Coal hopper 151 ・ ・ ・ Coal cutting device 16 ... Coal conveyor 17 ... Pellet conveyor

Continued on the front page (72) Inventor Kazuo Onuki 1 Nippon Steel Corporation, Hirohata-ku, Himeji-shi Nippon Steel Corporation Inside Hirohata Works (72) Inventor Hironori Naka 1-Fujimachi, Hirohata-ku, Himeji-shi Nippon Steel Corporation Inside the Hirohata Works (72) Inventor Tadashi Manabe 1 Fujimachi, Hirohata-ku, Himeji City Nippon Steel Corporation Inside the Hirohata Works, Ltd. F-term in Hirohata Works (reference) 4K001 AA10 BA02 CA21 CA23 CA26 GA12 GB01 GB02 HA01 4K012 DE01 DE02 DE03 DE06 DE08

Claims (9)

[Claims] 1. A method for operating a rotary bed furnace, wherein a carbonaceous material is mixed into a sedimentary layer formed on a rotary hearth during the operation of the rotary bed furnace for reducing agglomerates containing an iron oxide raw material. 2. An operation process of a rotary bed furnace, wherein the agglomerate is laid on a rotary hearth of a rotary bed furnace for reducing agglomerates containing an iron oxide raw material, and a carbonaceous material is charged into the rotary hearth. A method of laying agglomerates on a rotary hearth, wherein the carbonaceous material is mixed into a sedimentary layer formed on the rotary hearth. 3. A mixture of the agglomerate and carbonaceous material is laid on a rotary hearth of a rotary bed furnace for reducing agglomerates containing an iron oxide raw material, and is rotated during the operation of the rotary bed furnace. A method of laying agglomerates on a rotary hearth, wherein the carbonaceous material is mixed in a sedimentary layer formed on the hearth. 4. The method of laying agglomerates on a rotary hearth according to claim 2, wherein a carbonaceous material charging means is provided, and the carbonaceous materials are mixed with the agglomerate in a rotary hearth furnace. 5. The method according to claim 2, wherein the means for discharging the agglomerate after the reduction treatment provided in the rotary bed furnace is a scraping device such as a screw conveyor, a scraper or a pusher. Method of laying agglomerates on rotary hearth. 6. The carbonaceous material is coal, coke, char,
The method for laying agglomerates on a rotary hearth according to any one of claims 2 to 5, wherein the method is one or more kinds selected from the group consisting of oil coke, waste plastic and waste tire chips. 7. The carbon material mixed with the agglomerate in a ratio of not more than 20% by weight based on the agglomerate.
The method for laying agglomerates on a rotary hearth according to any one of the above. 8. A facility for reducing an agglomerate containing an iron oxide raw material and supplying one or both of the agglomerate and the carbonaceous material to a hearth of a rotary bed furnace for producing reduced iron. Agglomerate supply means for supplying the agglomerate, carbon material supply means for supplying a carbon material, agglomerate supplied from the agglomerate supply means and supplied from the carbon material supply means Feeder for producing reduced iron by a rotary bed furnace, comprising: a transfer means for transferring one or both of the carbonaceous materials to a rotary bed furnace. 9. A facility for supplying a carbonaceous material to a hearth of a rotary bed furnace for reducing agglomerates containing an iron oxide raw material and producing reduced iron, wherein the carbonaceous material supply means supplies the carbonaceous material. And a transfer means for transferring the carbon material supplied from the carbon material supply means to a rotary bed furnace, the carbon material supply facility for producing reduced iron using a rotary bed furnace.