JPH10204516A - Production of reduced iron and apparatus thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method which can produce reduced iron at high productivity by using a rotary hearth furnace, and to provide an apparatus therefor. SOLUTION: In the method for producing the reduced iron by burning mixed raw material of powdery ore and powdery coal in the rotary hearth furnace, the mixed raw material is charged from raw material charging devices 2-1-2-5 arranged at plural positions with interval along the shifting direction of the furnace hearth while rotating the furnace hearth (rotary hearth 1) and burnt. Plural mixed material layers are formed while forming the new mixed raw material layer and burnt. This method can easily be performed with this apparatus having plural raw material charging devices arranged with the interval.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing reduced iron by charging a raw material obtained by mixing fine iron ore and fine coal into a firing furnace having a rotating hearth.

[0002]

2. Description of the Related Art As a method for producing reduced iron mainly composed of metallic iron from a raw material obtained by mixing fine iron ore and fine coal, iron ores are produced by using a fluidized bed furnace or a moving bed type shaft furnace to produce natural gas or reduced gas. There are known a method of reducing with iron gas, a method of converting iron ore and coke into molten iron using a blast furnace, and cooling the molten iron to form pig iron. In these methods, iron ores are mainly reduced by gas reduction. However, in some cases, iron ores are provided with a reducing agent such as coal, and a direct reduction reaction is performed to increase the reaction efficiency. Something has been devised.

[0003] On the other hand, unlike the method of producing reduced iron by causing a reducing gas to act on such iron ores, a mixture of iron ore and a reducing material (such as coal) is used as a raw material.
A method of reducing by firing in a firing furnace maintained at １1400 ° C. is described in JP-B-45-19569.

According to this method, inexpensive coal is used in place of reducing gas, and pellets produced from a mixed powder of fine iron ore and fine coal are charged into a rotary bed type firing furnace maintained at a high temperature, and the cost is reduced to 1000. By maintaining the temperature at １1400 ° C. for about 10 minutes, iron oxide (Fe ₂ O ₃ ) in fine iron ore is converted into metallic iron (m-Fe) by hydrogen (H ₂ ) and carbon (C) in fine coal. It is a method characterized by reducing.

The rotary hearth furnace used in this method has a circular, donut shape as shown in FIG. 2, and has a structure in which a hearth 6 in a flat plate shape rotates. The furnace is entirely surrounded by refractory bricks 11 and is heated to a predetermined temperature by a plurality of combustion burners 9 installed horizontally. The rotary hearth furnace has one raw material charging device 7 formed in a direction perpendicular to the direction in which the hearth 6 moves, and three firing zones (from this position in the direction of rotation of the hearth 6). A, B and C) and one cooling zone (D), and an exhausting device 8 is provided in the cooling zone (D). Cooling zone (D)
Is provided with a water-cooled metal cooling plate 12 for quenching and solidifying a product that has been partially melted at a high temperature and easily fused. Reference numeral 13 denotes a flue, and reference numeral 14 denotes a driving device (electric motor) for rotating the hearth 6.
It is.

[0006] The pellet-shaped raw material 16 which has been dried in advance is charged into the furnace through the raw material charging device 7, and is heated and reduced while passing through three firing zones (A, B and C) in order. Then, Fe ₂ O ₃ changes to m-Fe, and is discharged from the mining device 8 through the final cooling zone (D) to the outside of the furnace and sent to another cooling device.

By the way, in order to produce reduced iron having a high metallization ratio (90 to 95%) from fine iron ore and fine coal, the temperature must be at least 900 ° C. or higher.
The higher the temperature, the faster the reaction rate. For this reason, in the above-described process, the heating rate of the raw material (that is, the heat applied to the raw material) determines the firing rate of the raw material, and the rotation speed of the rotary bed is determined in synchronization with the firing rate. Production speed is dominated. But,
When reducing Fe ₂ O ₃ in iron ore with H ₂ or C in coal, the amount of heat required to raise the temperature of the raw material to 1000 ° C. or more is several times the amount of heat required. More heat is required than at elevated temperatures.

In the above process, the heat for raising the temperature of the raw material is configured so that most of the heat is supplied by radiant heat from the upper brick surface of the rotating bed. this is,
If heat is supplied by convection of the gas, an oxidizing gas such as H ₂ O or CO ₂ generated by burner combustion comes into contact with metallic iron generated by firing, and a reoxidation reaction occurs. . In addition, since the next raw material is supplied immediately after the raw material is discharged by the rotary hearth structure, the floor brick surface hardly heats up, and the supplied raw material is almost supplied with heat from the bottom surface It is not in a state. Therefore, even though a large amount of heat is required as described above, the thermal efficiency in the above process is not necessarily high.

Further, a cooling zone is provided, in which a product heated to a high temperature is rapidly cooled by contact with a water cooling jacket (cooling plate), and further cooled by a cooling device provided separately. A significant portion of the active surface of the floor is occupied by this cooling zone, which inevitably reduces productivity. At the same time, the loss of heat energy released by cooling is large.

[0010]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems in the production of reduced iron using a rotary bed furnace using inexpensive coal as a reducing material. It is an object of the present invention to provide a method capable of increasing the firing rate and producing reduced iron at a high production rate, and an apparatus therefor.

[0011]

Means for Solving the Problems As a result of repeated studies to solve the above-mentioned problems, the present inventor has found that the supply of raw materials is performed by using a plurality of raw material charging devices arranged in a furnace. It was confirmed that the amount of heat transfer to the slag was increased and the firing rate was increased to improve the productivity. That is, by placing a new raw material on the fired product and forming a plurality of raw material layers, heat from the product can be used for heating the raw material, and the product can be cooled by using a low-temperature raw material. it can.
This also eliminates the need to provide a special cooling zone in the furnace, and can increase the productivity.

The present invention has been made based on the above findings, and the gist of the present invention is to provide a method for producing reduced iron according to the following (1):
And (2) in an apparatus therefor.

(1) In a method of producing reduced iron by firing a mixed raw material of fine iron ore and fine coal in a rotary hearth furnace, an interval is provided along a moving direction of the hearth while rotating the hearth. Cutting the mixed raw material from the raw material charging devices provided at a plurality of locations and firing the raw material, forming a plurality of layers while forming a new mixed raw material layer thereon, and firing the mixed raw material. Iron manufacturing method.

(2) An apparatus for producing reduced iron comprising a furnace for reducing iron ore by firing together with a reducing material, wherein the furnace comprises: a rotary bed rotatable on a horizontal surface; A plurality of burners for heating the raw material, a plurality of raw material charging devices for supplying raw materials provided at intervals on a rotary bed, and for discharging reduced iron obtained by firing out of the furnace. An apparatus for producing reduced iron, wherein the apparatus is a rotary bed furnace having an ore discharging device.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention (the inventions of the above (1) and (2)) will be described below in detail with reference to the drawings.

FIG. 1 shows the configuration of a main part of a rotary bed furnace (FIG. 1 (a)) used for carrying out the invention (1) (hereinafter, also referred to as the "method of the present invention"). FIG. 1 is a view schematically showing a deposition state of a raw material on a hearth when a method of the present invention is performed using a furnace (FIG. 1B). That is,
FIG. 1 (a) shows a rotary bed furnace (hereinafter, also referred to as "the apparatus of the present invention") constituting a main part of the apparatus of the above-mentioned (2).
FIG.

In FIG. 1 (a), reference numeral 1 denotes a hearth (rotating bed) that rotates in the direction of the arrow, and a plurality of raw material units for supplying raw materials onto the rotating bed 1 along the moving direction. Input devices are mounted at intervals. In this example,
A five-stage raw material charging apparatus denoted by reference numerals 2-1 to 2-5 is provided. Reference numeral 3 denotes an ore discharging device for discharging the fired product. Reference numeral 4 is a raw material hopper for storing the raw material sent from the Erich mixer 5 provided outside the rotary hearth furnace and distributing the raw material to each raw material charging device. Although not shown here, as shown in FIG. 2 above, the revolving floor 1 is entirely covered with refractory bricks, and a burner and a secondary air blower are provided at necessary places on the brick walls. Air injection tube is installed.

In order to produce reduced iron by sintering the raw material with this rotary bed furnace, first, fine iron ore and fine coal containing an appropriate amount of moisture are mixed well with an Erich mixer 5 to obtain a mixed raw material ( Hereinafter, it is simply referred to as “raw material”) and transferred to the raw material hopper 4. Next, the mixed raw material is divided into five parts and charged into the raw material charging devices 2-1 to 2-5, and cut out on the rotary bed 1 of a rotary bed furnace. It is preferable to cut out the raw material continuously in each raw material charging apparatus. This is because the formation of the raw material layer is performed uniformly, so that heat exchange between a fired product described later and a new raw material placed thereon is sufficiently performed. In addition, the cutting of the raw material when starting the firing by operating the furnace may be performed simultaneously with each raw material charging apparatus. Initially, a discontinuous portion occurs in the raw material layer, but after one rotation of the hearth, the raw material layer is kept in a steady loading state as shown in FIG.

In FIG. 1 (b), the fired product is discharged from the mining apparatus 3, and the raw material is supplied from the first-stage raw material charging apparatus 2-1 to the hearth (rotating bed 1) where the refractory brick is exposed. It is cut out to form a first-stage raw material layer. By the time the raw material in the first raw material layer reaches the position where the second raw material charging device 2-2 is provided, the temperature of the raw material in the first raw material layer is increased by burner heating from above and radiant heating from the brick surface, Be reduced.

As the reduction proceeds, the raw material has a metallization rate of about 90.
% Of the reduced iron, the raw material is newly cut out from the second-stage raw material charging device 2-2, and the raw material layer (first-stage layer), which has already been calcined, is cut out. Will be laid.
At this time, the lower fired product is rapidly cooled by the upper raw material, and the upper raw material is heated by the fired product from the lower surface, and heat exchange is performed between the two layers. The upper raw material is heated from the upper and lower surfaces by the burner heating from the top and the radiant heating from the brick surface, so that reduced iron has a metallization ratio of 90% or more in a shorter time than the first-stage raw material. Therefore, in the example shown in FIG. 1, the angle between the first-stage raw material charging device 2-1 and the second-stage raw material charging device 2-2 is 90 °, Eye material charging device 2
-2 and the angle between the adjacent raw material charging devices are all 9
It is configured to be smaller than 0 °.

Next, when the raw material in the second raw material layer is reduced iron having a metallization ratio of about 90% or more, the raw material is cut out from the third raw material charging device 2-3, and As in the case of the raw material of the stage, the lower calcined product is rapidly cooled, and the raw material of the upper side is heated from both upper and lower surfaces. Hereinafter, similarly, the raw materials charged by the raw material charging devices in each stage are sequentially laminated and fired.

The final, ie, fifth stage, raw material charging apparatus 2
After the firing of the charged raw material from −5, the fired products in the first to fifth stages are collectively discharged to the outside of the furnace by the ore discharging device 3.

In the above method of the present invention, since the distance until the firing is completed is shortened, the rotational speed of the hearth is lower than that of the conventional method.
Although the number of steps is increased as compared with the step charging, the number of steps is increased and the layer height is increased, so that the amount of firing per unit time is greatly increased. In the fired product immediately before the mining, the uppermost one (the fifth stage) is easily fused to each other at a high temperature, but the other parts (the first to fourth stages) are cooled and solidified. No special cooling zone is required because the cooled product and the top product are mixed during the ore. That is, in the method of the present invention,
The rotating bed can be used only for firing, the hearth can be used effectively, and the productivity can be improved.

The number of stages of the raw material charging apparatus is not particularly limited, but is preferably about five. This is because the effects of both-side heating and cooling are exhibited in the second and subsequent stages, so the more stages, the more the thermal efficiency improves, but the degree of the effect gradually decreases, and on the other hand, This is because the number of installed charging devices increases, and equipment costs increase, so that there is an appropriate number of stages.

There is no particular limitation on the intervals between the raw material charging devices provided at a plurality of locations.
Since the temperature of the raw material is increased and reduced between the adjacent raw material charging devices, it is desirable that the intervals be substantially equal. In addition,
The raw material cut out from the second-stage raw material charging apparatus is heated from both the upper and lower surfaces and becomes reduced iron in a shorter time than the first-stage raw material. Therefore, as illustrated in FIG. From the viewpoint of efficient use of the hearth, the interval between adjacent raw material charging devices after the charging device is set to be slightly smaller than the distance between the first and second raw material charging devices. More preferred.

The firing temperature of each stage may be 1000 to 1400 ° C. as in the conventional case. for that reason,
In the apparatus of the present invention, a plurality of burners and air injection tubes are mounted at required places in the furnace.

In the method of the present invention, pellets,
Briquettes, powders, etc. can be used. In addition, it is not limited to the pseudo particle state, but may be in the form of a flake state, a sheet state, or the like.

Conventionally, pellets have been widely used as a raw material, in order to secure a heating area by giving a surface area as large as possible. But,
In the method of the present invention, since heat exchange by contact between the calcined product and the charged raw material is important, the form of the raw material is preferably powder or sheet. Further, the thickness of the layer is preferably 5 to 30 mm. It is technically difficult to form a thin layer of less than 5 mm. On the other hand, if the layer is too thick and exceeds 30 mm, it takes a long time to raise the temperature of the raw material, even if it is heated on both sides, and the effect of improving productivity Is smaller.

According to the method of the present invention, it is possible to increase the amount of heat transferred to the raw material and at the same time to speed up the cooling of the product, thereby improving the firing rate and using the hearth only for firing. The productivity of reduced iron can be greatly improved. In addition, since the layer height per unit hearth area can be increased and the rotation speed of the hearth can be reduced, the life of the hearth brick can be extended.

This method can be easily implemented using the apparatus of the present invention.

[0031]

EXAMPLE 74% of fine iron ore and 25% of fine coal shown in Table 1
After blending 1% of bentonite as a binder and mixing with a mixer, and then adding water, pellets or briquettes, or powders, or flakes or sheets are used as raw materials. This was charged into a rotary hearth furnace to produce reduced iron, and the productivity was evaluated.

[0032]

[Table 1]

An Erich mixer was used for mixing the iron ore, the coal and the binder. For the production of pellets, a dish-type granulator was used, and for the production of briquettes, a briquette machine having a briquette-type groove in a double roll was used. The powder was not processed. Flakes and sheets were produced by flat double rolls without grooves. When the water content was 5%, the powder layer had no tackiness and was in a flake shape. However, when the water content was 10%, the powder layer was tacky and had a sheet shape.

For firing, the outer diameter is 2.0 m and the inner diameter is 1.0
A rotary hearth furnace with a m.

In the method of the present invention,
As shown in FIG. 1 above, a five-stage raw material charging apparatus was attached, and firing was performed without providing a cooling zone. That is, fine iron ore, fine coal, and bentonite are mixed with an appropriate amount of water by an Erich mixer 5 and then conveyed to a raw material hopper 4 where the raw material hopper is divided and cut out from five cutouts. Charger 2-1 to 2-5
Transferred to. Each raw material charging device can be equipped with a granulator for pellet production, or a double roll for forming briquettes, flakes, or sheets. After being formed into a shape or form, it was placed on a hearth. When a powdery raw material was used, the raw material was put on the hearth without passing through a double roll.

The charged raw materials move with the rotation of the hearth (rotary bed 1), and are stacked in layers from the first stage to the fifth stage as shown in FIG. 1B. . In each stage,
After firing at 1300 ° C., it was discharged by a discharge device.

On the other hand, for comparison, sintering was also carried out by using a pellet, using a raw material charging apparatus in one stage, and providing a water-cooling section for sintering. That is, as shown in FIG. 3 (a), after mixing the iron ore fines, the fine coals and the bentonite with the Eirich mixer 5, pelletize them with the dish-type granulator 17, dry them with the drying equipment 15, and mix the raw materials. The raw material is sent to the hopper 4 and put on the hearth 6 from the raw material charging device 7,
Fired at ℃. After firing, it was cooled and solidified by the water cooling plate 12 and discharged by the ore discharging device 8. Note that FIG.
FIG. 4 is a view schematically showing a state of deposition of raw materials on a hearth when the furnace shown in FIG.

In both the method of the present invention and the conventional method, the metallization ratio (m-Fe / T.Fe, where T.Fe is the total amount of iron in the raw material) ) Was determined by chemical analysis, and the rotation speed of the rotating bed was determined so that the metallization ratio was 90% or more.

Table 2 shows the results of the production rates obtained in various cases where the raw materials used were changed in the method of the present invention, and in the conventional method.

As is clear from the results, the production rate of reduced iron per unit area is remarkably improved by the method of the present invention. In particular, powdery or sheet-like raw materials are used rather than pellets or briquettes as raw materials. , Layer thickness 5-3
In the case of 0 mm, a particularly high production speed was obtained.

[0041]

[Table 2]

[0042]

According to the method of the present invention, the amount of heat transferred to the raw material can be increased, and at the same time, the cooling of the product can be accelerated, and reduced iron can be produced at a high production rate. Also,
It is also possible to extend the life of the hearth brick. This method can be easily implemented using the apparatus of the present invention.

[Brief description of the drawings]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an explanatory view of a rotary bed furnace used for carrying out the method of the present invention. FIG. 1 (a) shows a configuration of a main part of the rotary bed furnace, and FIG. It is a figure which shows typically the deposition state of the raw material on the hearth at the time of implementing a method.

FIG. 2 is a view showing a configuration of a main part of a rotary bed furnace used in a conventional method, where (a) is a longitudinal sectional view including the center of the furnace, and (b) is a sectional view taken along a line II shown in (a). It is a cross section of the whole furnace.

FIG. 3 is an explanatory view of a rotary bed furnace used in a conventional method,
(A) is a diagram showing a configuration of a main part of the furnace, and (b) is a diagram schematically showing a deposition state of raw materials on a hearth when the furnace is used.

[Explanation of symbols]

 1: rotating bed 2-1 to 2-5: raw material charging device 3: mining device 4: raw material hopper 5: Erich mixer 6: hearth 7: raw material charging device 8: mining device 9: burner 10: Air injection pipe 11: Refractory brick 12: Cooling plate 13: Flue 14: Drive unit 15: Drying equipment 16: Raw material 17: Dish granulator

Claims (2)

[Claims] 1. A method for producing reduced iron in which a mixed raw material of fine iron ore and fine coal is fired in a rotary hearth furnace, wherein the hearth is rotated and spaced along the moving direction of the hearth. Reducing iron, wherein the mixed raw material is cut out and fired from a raw material charging device provided at a plurality of locations, and a plurality of layers are formed and fired while a new mixed raw material layer is formed thereon. Manufacturing method. 2. An apparatus for producing reduced iron comprising a furnace for reducing iron ore by firing together with a reducing material, wherein the furnace comprises: a rotary bed rotatable in a horizontal plane; A plurality of burners for heating, a plurality of raw material charging devices for supplying raw materials provided at intervals on a rotary bed, and a plurality of raw material charging devices for discharging reduced iron obtained by firing out of the furnace; An apparatus for producing reduced iron, which is a rotary bed furnace having an ore discharging device.