JPH11193406A - Ironmaking method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the ironmaking cost, to reasonably improve the ironmaking capacity, and to increase the service life of a blast furnace by complementing the blast furnace method with the iron-bath type melting and reducing method in one ironmaking equipment. SOLUTION: In using the iron-bath type melting and reducing method in a mode to complement the blast furnace method by paying attention to the fact that the iron-bath type melting and reducing method has no restriction in the grain size of the raw material, and by feeding sintered ore and cokes small in grain size which cannot be used or is difficult to use in operation in the blast furnace method to the iron-bath type melting and reducing furnace as the raw material, the sintered ore and cokes for steel-making large in grain size among the sintered ore manufactured by a sintering machine and the cokes for steel-making are fed to the blast furnace, and the sintered ore and cokes for steel-making small in grain size are fed to the iron-bath type melting and reducing furnace.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for making pig iron in an iron making facility provided with a blast furnace and an iron bath type smelting reduction furnace.

[0002]

2. Description of the Related Art Generally, an iron making facility having a blast furnace is provided with a sintering machine and a coke oven, and the sinter and coke produced in the sintering machine and the coke oven are supplied to the blast furnace to produce hot metal. Done. In such an iron making method using a blast furnace (blast furnace method), sintered ore having a small particle size cannot be used in order to secure air permeability in the furnace. For this reason, the sintered ore produced by the sintering machine is sieved, and those having a small particle size are re-sintered as return ore. Therefore, the production yield of the sintered ore is generally about 85%. Regarding coke, coke with a small particle size cannot be used in a blast furnace for the same reason, coke produced in a coke oven is sieved, and coke with a small particle size is used for producing sintered ore. I have.

On the other hand, in the iron making method using an iron-bath smelting reduction furnace (iron-bath smelting reduction method), there is no need for a pretreatment such as the blast furnace method for ore and carbonaceous material, and the ore and coal itself are used as raw materials. Although it can be used, it is necessary to supply ore and coal to a furnace that is operated in a closed state, so that in order to prevent ore and coal from adhering in the supply system, powder ore or When powdered coal is used, a step of drying in advance and equipment for the step are required.

[0004]

In contrast to such a conventional iron making method, the present invention complements the blast furnace method with an iron bath type smelting reduction method in one iron making facility, thereby reducing iron making costs. Another object of the present invention is to provide a new iron making method capable of improving and optimizing the iron making capacity and extending the life of the blast furnace.

[0005]

As described above, the iron bath type smelting reduction method has the greatest advantage that ore or carbon material does not require a pretreatment such as the blast furnace method. Has attracted attention as an alternative to the blast furnace method. The present inventors have focused on the fact that, apart from the advantages of the iron bath type smelting reduction method generally considered heretofore, the ironmaking method has no restriction on the particle size of the raw material as in the blast furnace method. In order to complement the blast furnace method, small-sized sinters that cannot be used in the blast furnace method or are difficult to use in operation are supplied to the iron-bath smelting reduction furnace as raw materials. We considered using the iron bath type smelting reduction method in a simple form.

[0006] In the iron making method of such a form, since the iron making using the sinter of the fine grain side as a raw material is shared by an iron bath type smelting reduction furnace, the entire amount of the produced sinter is as it is, It can be used as a raw material for iron making without generating return ore,
For this reason, the production amount of hot metal can be increased as compared with the conventional blast furnace method alone operation. On the other hand, it is also possible to operate the blast furnace with a low tapping ratio, thereby reducing the heat load of the blast furnace and greatly extending the life of the blast furnace. In addition, when the sintered ore is used in the iron-bath smelting reduction method, the ore drying step is not required at all, so that the iron-bath smelting reduction method can be performed very advantageously. Furthermore, since CaO / SiO ₂ is adjusted to around ₂ in the production process of sinter, if this is used as an iron source in an iron bath type smelting reduction method, slag components such as quicklime and dolomite are adjusted. It is not necessary to use a solvent for the purpose.

The present inventors have also noticed that there is no restriction on the particle size of the carbonaceous material used in the iron-bath smelting reduction method as in the blast furnace method, and that the coke for iron making cannot be used in the blast furnace method. We considered supplying small-sized coke, which is difficult to use in operation, as carbon material to the iron-bath smelting reduction method. According to such a use form of coke, not only can coke fine powder that cannot be consumed in the production process of the sintered ore be effectively utilized, but also if the coke is used by the iron bath type smelting reduction method, Since there is no need for a drying step for the material, the iron bath type smelting reduction method can be carried out extremely advantageously, and the secondary combustion rate can be greatly increased as compared with the case where coal is used as the carbon material, and the furnace , The heat load of the iron-based smelting reduction method can be reduced, and the productivity can be improved.

Further, in the iron making method of supplying sinter having a small particle size as a raw material to the iron-bath smelting reduction method as described above, since there is basically no return ore in a sintering machine, It is conceivable that the amount of coke breeze used in the sintering process is reduced as compared with the case of the single operation of the blast furnace method, and that the coke breeze becomes excessive. Therefore, in such an iron making method, by using a part of the coke breeze of the iron making coke as a carbon material in the iron bath type smelting reduction method, a blast furnace, an iron bath type smelting reduction furnace and a sintering machine are used. In a steelmaking facility equipped with a coke, coke including powdered coke can be effectively used in a well-balanced manner.

The present invention has been made based on the above ideas and findings, and has the following features. [1] In an iron making facility equipped with a blast furnace, an iron-bath smelting reduction furnace and a sintering machine, of the sinters produced by the sintering machine, large-sized sinters are supplied to the blast furnace, and A method for producing pig iron, comprising supplying sinter to an iron-bath smelting reduction furnace. [2] In an iron making facility equipped with a blast furnace and an iron-bath smelting reduction furnace, it is necessary to supply large-grain coke to the blast furnace and supply small-grain coke to the iron-bath smelting reduction furnace. Characteristic iron making method.

[3] In an iron making facility equipped with a blast furnace, an iron-bath smelting reduction furnace and a sintering machine, of the sinters produced by the sintering machine, large-sized sinters are supplied to the blast furnace, Along with supplying small-grained sinter to iron-bath smelting reduction furnaces, supply large-grained coke to blast furnaces and supplying small-grained coke to iron-bath smelting reduction furnaces. Characteristic iron making method.

[4] In the pig ironing method according to the above [1] or [3], the sintered ore produced by the sintering machine is sieved with a sieve having a size of 3 mm or more, and the sintered ore under the sieve is subjected to an iron bath. A method for producing iron, comprising supplying the molten iron to a smelting reduction furnace. [5] The iron making method according to [2] or [3], wherein the iron-making coke is sieved with a sieve having a size of 20 mm or more, and the coke under the sieve is supplied to an iron-bath smelting reduction furnace. Iron making method. [6] The iron making method according to any one of [1] to [5], wherein the blast furnace is operated at a tapping ratio of 1.0 to 1.7 t / m ² / day.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention is a pig iron making method based on an iron making facility provided with a blast furnace, an iron bath type smelting reduction furnace and a sintering machine, and a sintering process (sintering machine). ), The sintered ore with large grain size (mainly lump ore) is supplied to the blast furnace, and the sintered ore with small grain size (mainly powdery ore) ) To an iron-bath smelting reduction furnace,
The hot metal is manufactured in each furnace.

Usually, in such a pig iron making method, a sintered ore produced by a sintering machine is sieved through a suitable sieve to obtain a sintered ore having a large particle size including a lump ore and a particle size larger than that. And sinters are supplied to a blast furnace and an iron-bath smelting reduction furnace, respectively. The branch point of the particle size of the sintered ore to be supplied to the blast furnace and the iron bath type smelting reduction furnace may be generally set to the sieving particle size at the time of sorting the return ore, but a larger sieving particle size may be used as the branch point. Good. In the blast furnace, the use of sintered ore having a large particle size as much as possible facilitates operation in terms of air permeability and the like, and is advantageous in terms of economy, production efficiency, and the like.

In general, a sieving particle size of 3 mm or more is required for charging the blast furnace. Therefore, the branch point of the particle size of the sinter supplied to the blast furnace and the iron bath type smelting reduction furnace is determined by sieving. A particle size of 3 mm or more, that is,
Sintering the ore produced by the sintering machine with a sieve of 3 mm or more, supplying the ore on the sieve to the blast furnace, and supplying the ore under the sieve to the iron bath type smelting reduction furnace Is preferred. Further, the branch point (sieving particle size) of the particle size of the sintered ore is more preferably 5 m.
m or more, particularly preferably 8 mm or more, whereby a sintered ore having a particularly suitable particle size can be supplied to the blast furnace side.

However, the sinter does not need to supply all of the sinter having the particle size that can be supplied to the blast furnace to the blast furnace. It does not matter at all that the blast furnace side contains sinter of a particle size that can be supplied.
In short, it suffices to prevent sinter ore with a particle size inappropriate for charging into the blast furnace equivalent to return ore from being supplied to the blast furnace side,
As long as such conditions are satisfied, the branch point of the particle size of the sinter supplied to the blast furnace and the iron-bath smelting reduction furnace can be arbitrarily set in consideration of the amount of the sinter supplied to both furnaces. . In addition,
Generally, it is inevitable that the sintered ore on the screen after sieving contains particles having a particle size smaller than the sieving particle size to some extent. Needless to say, the case including the particle size distribution is included.

FIG. 1 shows the ore supply particle size distribution of the raw ore (sinter feed) of the sinter, and the sinters under and after sieving the sinter produced from the raw ore. 1 shows an example of the particle size distribution of the sample. In this example, the sieving ore was screened by setting the sieving particle size (sieving) to 6 mm. In the figure, A represents the ore supply particle size distribution, and B represents the particle size distribution of the sinter under the sieve. And C indicates the particle size distribution of the sintered ore on the sieve. According to the method of the present invention, the sinter under the sieve having the particle size distribution of B is supplied to the iron bath type smelting reduction furnace, and the sinter on the sieve having the particle size distribution of C is supplied to the blast furnace, and are introduced into the furnace interior. You.

In the iron-bath smelting reduction furnace, the iron source charged into the furnace is rapidly melted by the combustion of the carbonaceous material by oxygen, and the carbonaceous material or C in the carbonaceous material is carburized by molten iron or granulated pig iron. The iron gas is reduced quickly, and the CO gas generated there is promptly secondary-combusted with oxygen gas, so that iron making with good thermal efficiency and low fuel consumption unit and energy consumption unit is performed.

Generally, the iron bath type smelting reduction equipment is provided with a pre-reduction furnace (usually a fluidized bed type pre-reduction furnace) for pre-reducing ore, and the ore is pre-heated and pre-reduced by this pre-reduction furnace. (Usually, a pre-reduction rate of 10 to 30%) is charged into an iron-bath smelting reduction furnace to reduce the unit consumption of coal and oxygen, and the productivity is 10 to 50 as compared with the case where pre-reduction is not performed. % Is also improved. Therefore, also in the method of the present invention, it is preferable that the ore is preliminarily reduced in the prereduction furnace and then charged into the iron bath type smelting reduction furnace. If the ore is preheated before the preliminary reduction in the preliminary reduction furnace, the productivity can be further improved. In this iron-bath smelting reduction method, the iron-bath smelting reduction furnace and the preliminary reduction furnace do not have the same restrictions as the blast furnace on the particle size of the ore that is the iron source.
Even if a sintered ore having a small particle size as in the present invention is charged, the smelting reduction can be performed without any problem.

Further, when sinter is used as an iron source in the iron bath type smelting reduction method as described later, it is unnecessary to dry the ore as in the conventional iron bath type smelting reduction method. However, for that purpose, it is necessary that the produced sintered ore does not absorb excessive moisture before being charged into the iron bath type smelting reduction furnace (for example, a water absorption rate of 1% or less). Therefore, for the sintered ore to be supplied to the iron-bath smelting reduction furnace among the manufactured sinters, consideration should be given to not absorbing moisture as much as possible during handling before charging the iron-bath smelting reduction furnace, for example, At the time of storage, it is necessary to take measures such as providing a rain-proof ceiling.

The iron making method of the present invention having such a configuration has the following advantages as compared with the conventional blast furnace method alone. First, in order to share the ironmaking using the sinter of the fine-grain side among the sinters produced by the sintering machine with the iron bath type smelting reduction furnace, the entire amount of the produced sinter is intact.
In other words, it can be used as a raw material for making iron without generating return ore. For this reason, when the production capacity of the sintering machine is equivalent to that of the conventional blast furnace method alone operation, the supply of raw ore is increased by the amount of return ore that has occurred conventionally, and it is possible to increase hot metal production, Ironmaking productivity can be increased.

On the other hand, when the production amount of the hot metal is made equal to that of the conventional operation of the blast furnace method alone, it is possible to operate the blast furnace with a low tapping ratio, thereby reducing the heat load of the blast furnace. As a result of effectively suppressing damage inside the furnace, the life of the blast furnace can be greatly extended. In this case, the blast furnace Dezukuhi 1.0~1.7t / m ³ / day about (particularly preferably, 1.4t / m ³ / day before and after) it is preferable to operate with. In a conventional large blast furnace exceeding 2000 m ³ , the tapping ratio is 2.0 t / m due to oxygen enrichment.
^{Although the} operation is performed at ³ / day or more, even if the tapping ratio is 1.7 t / m ³ / day or less by applying the method of the present invention, the same iron production as that of the conventional blast furnace method alone operation can be achieved. And a tapping ratio of 1.7 t / m
By operating at ³ / day or less, the heat load of the blast furnace is reduced, and the life of the blast furnace can be greatly extended. However, when the tapping ratio of the blast furnace is less than 1.0 t / m ³ / day, the effect of extending the furnace age is saturated and the productivity is rather uneconomical. From the above viewpoint, it is considered that the optimum value of the tapping ratio is around 1.4 t / m ³ / day.

In the iron making method of the present invention of the above-described embodiment, if the sintered ore after being manufactured is charged into an iron bath type smelting reduction furnace without absorbing moisture, it is necessary for a normal iron bath type smelting reduction method. No ore drying step is required at all, so that the iron bath type smelting reduction method can be carried out at low cost. Furthermore, when using sinter as an iron source in the iron bath type smelting reduction method,
Since CaO / SiO ₂ is adjusted to around ₂ in the production process of sinter, it is easy to adjust the slag basicity without charging a medium solvent such as quicklime or dolomite as an auxiliary material into the furnace. The raw material cost and the fuel consumption rate can be reduced as compared with the case where ore is used as the iron source, and the productivity can be improved in this aspect as well. In the method of the present invention, it goes without saying that, in addition to the sintered ore, an iron source such as ore, scrap, direct reduced iron, and iron anchor hydride can be used as the iron source to be charged into the iron-bath smelting reduction furnace.

A second aspect of the present invention is a steelmaking facility provided with a blast furnace and an iron-bath smelting reduction furnace, wherein, among the ironmaking coke, coke having a large particle size (mainly lump coke) is used in the blast furnace. Coke having a small particle size (mainly powdered coke) is supplied to an iron-bath smelting reduction furnace and used as a carbonaceous material. The coke for iron making used may be any of coke produced in a coke oven in a steel making facility and coke supplied from outside the steel making facility.

Usually, in such an iron making method, coke for iron making is sieved through a suitable sieve to separate coke having a large particle size including large coke and coke having a smaller particle size. And supplied to the iron bath type smelting reduction furnace as carbon material. The branch point of the particle size of coke supplied to the blast furnace and the iron-bath smelting reduction furnace is the same as in the case of the sinter described above, and in general, the coke having a particle size unsuitable for charging in the conventional blast furnace method is selected. The sieving particle size at that time may be used, but a sieving particle size larger than that may be used as the branch point.

In general, charging coke into a blast furnace requires a sieving particle size of 20 mm or more. For this reason, the branch point of the particle size of the coke supplied to the blast furnace and the iron bath type smelting reduction furnace is determined by sieving. Particle size of 20 mm or more, that is, ironmaking coke is sieved with a sieve of 20 mm or more, coke on the sieve is supplied to the blast furnace, and coke under the sieve is supplied to the iron-bath smelting reduction furnace. Is preferred.
The branch point of the coke particle size (sieving particle size) is more preferably at least 25 mm, particularly preferably at least 30 mm, so that coke having a particularly suitable particle size can be supplied to the blast furnace side.

However, it is not necessary to supply all the coke having a particle size that can be supplied to the blast furnace to the blast furnace, and the coke can be supplied to the blast furnace during the coke under the sieve to be supplied to the iron bath type smelting reduction furnace. Inclusion of coke of a fine particle size is not a problem. In short, it suffices to prevent coke of a particle size inappropriate for charging the blast furnace from being supplied to the blast furnace side, and as long as such conditions are satisfied, the branching of the particle size of the coke supplied to the blast furnace and the iron-bath smelting reduction furnace The point can be set arbitrarily in consideration of the amount of coke supplied to both furnaces. In general, it is unavoidable that the coke on the screen after sieving contains particles having a particle size smaller than the sieving particle size to some extent, and in the present invention, the coke supplied to the blast furnace side has such a particle size distribution. Needless to say, it also includes the case of having.

When coke is used as a carbon material in the iron-bath smelting reduction method as described later, the drying of the carbon material (coal) as in the conventional iron-bath smelting reduction method is performed. Although it becomes unnecessary, it is necessary that the produced coke does not absorb excessive moisture until it is charged into the iron-bath smelting reduction furnace (for example, a water absorption rate of 1% or less). Therefore, coke to be supplied to the iron-bath smelting reduction furnace among the coke for iron-making should be designed so that it does not absorb moisture as much as possible during handling before charging it into the iron-bath smelting reduction furnace. It is necessary to give consideration to the provision of ceilings.

The iron making method of the present invention having such a configuration has the following advantages as compared with the conventional blast furnace method alone. That is, first, iron coke produced in a coke oven inside a steelmaking facility or supplied from outside the steelmaking facility contains a considerable amount of fine coke that cannot be used in a blast furnace. Of such fine coke, Effective use of coke that cannot be consumed in the sinter production process can be achieved. In addition, if the coke after production is charged into an iron-bath smelting reduction furnace so as not to absorb moisture, there is no need for a carbon material drying step required in a normal iron-bath smelting reduction method. The iron bath type smelting reduction method can be performed at low cost.

Further, when coke is used as the carbon material in the iron bath type smelting reduction method, the secondary combustion rate of the gas generated in the furnace can be greatly increased as compared with the case where coal is used as the carbon material. That is, the secondary combustion rate when coal is used as the carbon material in the iron-bath smelting reduction method is at most about 30 to 40%, whereas when the coke is used as the carbon material, the secondary combustion rate is reduced. Since it can be about 50 to 80%, it is possible to reduce the unit fuel consumption and improve the productivity in the smelting reduction. In addition, coke has much higher fixed carbon than coal, and is less prone to thermal cracking and less likely to scatter from inside the furnace. This helps promote carburization in iron-bath smelting reduction, and is effective in increasing productivity and stabilizing operations. It is a target. In addition, since the coke has a lower hydrogen content than coal, the H ₂ O concentration in the exhaust gas is about several percent to 10% as compared with 10 to 25% when coal is used, and C is a gas that affects gas radiation.
O, large H ₂ O concentration in the most influential of CO _2, H ₂ O is for much lower compared to when using coal, it is possible to post combustion ratio is smaller heat load of the furnace if the same. Therefore, the heat loss can be reduced, and the fuel consumption rate can be reduced from this point.

According to a third aspect of the present invention, there is provided a steelmaking facility provided with a blast furnace, an iron-bath type smelting reduction furnace and a sintering machine, in which ironmaking is simultaneously performed in the first and second modes. Of the sintered ore produced in the sintering process (sintering machine), the sintered ore with large grain size (mainly lump ore) is supplied to the blast furnace, Ore (mainly powdery sintered ore) is supplied to an iron-bath smelting reduction furnace, and coke with a large grain size (mainly lump coke) is supplied to a blast furnace for ironmaking coke. In addition, coke having a small particle size (mainly powdered coke) is supplied to an iron-bath smelting reduction furnace, and hot metal is produced in each furnace.

The conditions for selecting and operating the sintered ore and the coke in the iron making method of this embodiment are the same as those described in the first embodiment.
This is the same as the case of the iron making method of the second embodiment and the second embodiment.
As mentioned earlier, in the ironmaking method in which small ore with a small grain size is supplied as an iron source to the iron bath type smelting reduction method, there is basically no return ore in the sintering machine. It is conceivable that the amount of coke breeze used in the sintering process is reduced as compared with the case of (1), and the coke breeze becomes excessive accordingly. Therefore, in such an iron making method, by using a part of the coke breeze of the iron making coke as a carbon material in the iron bath type smelting reduction method, a blast furnace, an iron bath type smelting reduction furnace and a sintering machine are used. In the iron making facility provided with the above, coke, in particular, fine-grain coke mainly composed of powdered coke can be effectively used in a well-balanced manner.

The smelting reduction method to which the method of the present invention can be applied is an iron bath type smelting reduction method in which the generated gas undergoes secondary combustion in a closed furnace. Since the smelting reduction method in which the iron source and the carbonaceous material are fed into a gasification melting furnace after reduction in a shaft furnace is required to be in a lump, the method of the present invention cannot be applied.

[0033]

EXAMPLES Table 1 shows an example of operation in an iron bath type smelting reduction furnace. Among them, Example 1 of the present invention was an example in which a hot metal was manufactured using a sintered powder (a sintered ore under a sieve having a sieve of 5 mm) corresponding to return ore as an iron source and using coal as a carbon material, and Example 2 of the present invention. Uses iron ore as an iron source and coke breeze (20 m
The present invention example 3 is a sintered powder (sieving mesh 4 m) corresponding to a return ore as an iron source.
This is an example in which hot metal was manufactured using coke breeze (coke under a sieve with a sieve of 20 mm) as a carbonaceous material using sinter under a sieve under a m. Further, a comparative example is an example in which hot metal was manufactured using iron ore as an iron source and coal as a carbonaceous material.

According to Table 1, in Example 1 of the present invention using the sintered powder corresponding to the return ore as the iron source, the ore drying step (steam for ore drying) is not required at all, and the calcined lime is not required. Since there is no need to load light or light dolomite, the economic effect is great. Further, the fuel consumption rate can be reduced as compared with the comparative example, and the production amount can be increased accordingly. Further, in Example 2 of the present invention using coke breeze as a carbon material, a coal drying step (steam for coal drying) is not required at all, and the fuel consumption rate can be reduced as compared with Example 1 or more. Can be further increased. Furthermore, in Example 3 of the present invention using sintered powder corresponding to return ore as an iron source and using coke breeze as a carbon material, both the ore and coal drying steps were not required at all, and The unit fuel consumption can be reduced to one or more, and the production amount can be further increased.

[0035]

[Table 1]

[0036]

[Table 2]

[0037]

According to the present invention described above, the blast furnace method is complemented by the iron bath type smelting reduction method in one iron making facility, and the iron ore smelting reduction furnace has a small particle size sintered ore which cannot be used in the blast furnace. Since ironmaking is manufactured using coke, it is possible to reduce ironmaking costs, improve and optimize ironmaking capacity, and extend the life of blast furnaces.

[Brief description of the drawings]

FIG. 1 is a graph showing an example of the particle size distribution of the ore raw material ore and the particle size distribution of each of the sintered ore under and after sieving the produced ore.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Terutoshi Sawada 1-2-1, Marunouchi, Chiyoda-ku, Tokyo, Japan Inside Nihon Kokan Co., Ltd. (72) Inventor Takeshi Sekiguchi 1-2-1, Marunouchi, Chiyoda-ku, Tokyo, Japan (72) Inventor Masayuki Watanabe 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Nihon Kokan Co., Ltd.

Claims (6)

[Claims] In an iron making facility provided with a blast furnace, an iron-bath smelting reduction furnace and a sintering machine, among the sinters produced by the sintering machine, large-sized sinters are supplied to the blast furnace, A method for making pig iron, comprising supplying a sintered ore having a small diameter to an iron bath type smelting reduction furnace. 2. In an iron making facility provided with a blast furnace and an iron-bath smelting reduction furnace, of the iron-making coke, large-grain coke is supplied to the blast furnace, and small-grain coke is supplied to the iron-bath smelting reduction furnace. An iron making method characterized by the above-mentioned. 3. An iron making facility provided with a blast furnace, an iron bath type smelting reduction furnace, and a sintering machine. In addition to supplying small ore sinter to iron-bath smelting reduction furnace, large-sized coke of ironmaking coke is supplied to blast furnace, and small-grain coke is supplied to iron-bath smelting reduction furnace. Iron making method. 4. The sinter produced in a sintering machine is sieved with a sieve of 3 mm or more, and the sinter under the sieve is supplied to an iron-bath smelting reduction furnace. Or the iron making method according to 3. 5. The iron making method according to claim 2, wherein the coke for iron making is sieved with a sieve having a size of 20 mm or more, and the coke under the sieve is supplied to an iron-bath smelting reduction furnace. 6. A blast furnace having a tapping ratio of 1.0 to 1.7 t / m ³ /
4. The method according to claim 1, wherein the operation is performed on day.
6. The iron making method according to 4 or 5.