JPH0621300B2 - Sintering method of iron ore - Google Patents

Description

The present invention relates to a method for sintering iron ore.

[Conventional technology]

In blast furnace operation, the properties of sinter are especially reducible (JIS-M87
The reduction rate specified in 13) is required to be good. Generally, if the low-temperature reductive pulverization property of sinter is remarkable, it will be reduced and pulverized at the upper part of the blast furnace shaft (around 300 to 700 ° C). , Instability in the furnace is caused by hanging. On the other hand, the sinter charged into the blast furnace is reduced by the ascending gas mainly containing CO while it is present in the form of lumps, and then dissolved, and the unreduced part is directly reacted with the red hot coke to be reduced. . Therefore, the higher the reduction rate immediately before melting, the less the consumption of coke, and the lower the fuel ratio in the blast furnace.

In order to improve the reducibility of sinter, in the production of sinter, the coke powder was adjusted appropriately for the fuel blending ratio and the sintering temperature was compared from the traditional 1350 to 1450 ℃ to 1200 to 1300 ℃. It has been proposed and is being implemented to lower the FeO content in the sinter by setting a relatively low temperature.

[Problems to be solved by the invention]

When carrying out a method for producing a sinter in which the sintering temperature is lowered to reduce the amount of FeO, there arises a problem that the use of refractory iron ore is limited. Iron ores differ in mineral composition and origin depending on the brand, and are easily assimilated when subjected to sintering treatment,
There is something difficult to do. For example, Australian iron ore is generally easy to assimilate, and South African iron ore is generally difficult to assimilate. Under various circumstances, it is the actual situation that various types of iron ore are mixed and used for sintering, but it is difficult to assimilate during the sintering process and tend to remain in the sintered ore in the form of natural ore. In the case of blending a dense and refractory iron ore with a certain amount, even if it is attempted to lower the FeO content in the sintered ore by lowering the sintering temperature, there will be a limit. Therefore, in order to obtain a sinter having good reducibility, it is necessary to limit the compounding amount of such refractory iron ore.

An object of the present invention is to produce a sinter having a good reducibility even if such a refractory iron ore is blended under the same sintering conditions as the conventional one.

[Means for solving problems]

The present invention achieves the above-mentioned object when an iron ore composed of a plurality of brands is used as a main raw material, and a miscellaneous raw material (for example, return ore), an auxiliary raw material and a solid fuel are mixed to obtain a sintering raw material. As a prescription, the above-mentioned refractory iron ore brands are selected from other iron ore brands, and the selected refractory iron ores are mixed with limestone or limestone and quick lime as a part of auxiliary materials, and solid fuel. FeO in the mixture by mixing coke powder as a part and FeO-containing dust generated in the steel mill
The content was adjusted to 0.2% by weight or more, and water was added to this to granulate, and the granulated product was used as the remaining brand of iron ore, return ore,
It is characterized in that it is mixed with the auxiliary raw material and the solid fuel to obtain a sintering raw material, and the obtained sintering raw material is supplied to a sintering machine for sintering.

Here, "hardly soluble iron ore" means, as described above, a natural ore that is hard to assimilate during the sintering process when sintered by the conventional method at a sintering temperature of 1200 to 1300 ° C. It is a dense, infusible iron ore that tends to remain in the ore.
Further, the method of the present invention is premised on sintering using a Dwightroid type sintering machine which has been widely used.

More specifically, among the main raw iron ore brands, the dense refractory iron ore is not blended as it is in powder form, but lime, coke and FeO
It is blended after granulating with dust. The lime compounded with the refractory iron ore at the time of this granulation may be limestone alone, or may be a mixture of limestone and quick lime, which is originally planned to be compounded in all sintering raw materials. It can be present in this granulated product as part of the auxiliary raw material. In addition, the coke powder that is present in the granulated product is also present as a part of the solid fuel to be blended in all the sintering raw materials.

One of the features of the present invention is to add FeO-containing dust to the granulated product. As shown in Table 1, an example of the dust collected in the steel mill is
It usually contains O. In the present invention, such FeO-containing dust is mixed with refractory iron ore together with lime and coke to form a granulated product having a FeO content of 0.2% or more.

By mixing this FeO-containing dust with dense refractory iron ore together with lime and coke and granulating, FeO, lime and coke will exist in the immediate vicinity of the refractory iron ore particles. , When this is blended in the sintering raw material and sintered, a low-melting point melt can be formed around the refractory iron ore particles in the granulated material. It can promote the assimilation of natural iron ore. As a result, even if the natural ore that remains in the sintered product as a huge hematite crystal in the conventional low temperature sintering method is changed into calcium ferrite and fine hematite even under the same low temperature sintering conditions. Therefore, it was found that a sintered ore with good reducibility can be obtained.

FIG. 1 is a flow chart of a manufacturing process according to the present invention. Of the four starting materials in the basic flow indicated by A on the right side, which are the powdery iron ore, the return ore, the auxiliary raw material, and the solid fuel, the dense refractory iron ore is selected and used for the system B. The limestone (or limestone and quick lime) and the solid fuel used in the B system can pass a part of the auxiliary raw material of the A system and a part of the solid fuel to the B system. In the system B, first, the refractory iron ore, lime, and coke powder are mixed with FeO-containing dust so that the FeO content in the mixture is 0.2% by weight or more, and water is added for granulation. Then, the obtained granulated product is mixed with powdered iron ore which is four kinds of starting materials of A, return ore, auxiliary raw materials and solid fuel together, or a mixture of these four kinds of starting materials. Mix. Here, the auxiliary material refers to serpentine, silica sand, limestone, and the like. The solid fuel is usually coke flour.

〔Example〕

Example 1 Table 2 shows the mixing ratio of the sintering raw material of this example. The conventional method (A ₀ ) in Table 2 corresponds only to the A system in FIG. 1, and in this case, the powdery iron ore raw material was also blended with the dense refractory iron ore as it was. It is a thing. As shown in Fig. 1, B in Table 2 selects the refractory iron ore from the powdered iron ore, and takes a part of the limestone and coke powder in the system A, and further contains FeO dust. It is a mixture of. This B was granulated by adding water and then mixed with other raw materials in the first mixer as shown in the flow chart of FIG. The sintering raw materials of the conventional method and the method of the present invention were loaded in the same sintering machine, and both were sintered under the same sintering conditions. The obtained sinter was subjected to a test according to JIS-M8713, and its reduction rate was investigated. The results are shown in Table 3. The production rate is also shown in Table 3.

From the results of Table 3, it can be seen that according to the method of the present invention, a sinter having a reduction rate increased by about 3% was obtained under the same production rate as in the conventional method.

Example 2 The blending ratio of easily meltable Australian iron ore was decreased and the blending ratio of refractory South African iron ore was increased, and FeO-containing dusts having different FeO contents were used. Except for the above, five kinds of sintering raw materials were prepared in the same manner as in Example 1, and these were sintered under the same sintering conditions. The blending ratio is shown in Table 4 on the same basis as in Example 1. Table 5 shows the production rate and reducibility of each sintered product.

From the results in Table 5, it can be seen that according to the method of the present invention, the reduction rate could be increased without lowering the production rate even when the blending ratio of the refractory iron ore was increased to about 18%.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a process drawing for explaining the manufacturing process of the method of the present invention.

Claims (1)

[Claims] 1. A main raw material is iron ore composed of a plurality of brands,
In mixing this with miscellaneous raw materials, auxiliary raw materials and solid fuel to obtain a sintering raw material, the brands of refractory iron ore are selected from the brands of other iron ores, and the selected refractory iron ores are Limestone or limestone as a part of the above-mentioned raw materials and quicklime, coke powder as a part of solid fuel, and FeO-containing dust generated in the iron mill are mixed to make the FeO content in the mixture 0.2% by weight or more. Then, water was added to this to granulate, and the granulated material was blended with the remaining brands of iron ore, miscellaneous raw materials, auxiliary raw materials, and solid fuel to obtain a sintering raw material. Sintering method of iron ore consisting of supplying to a sintering machine and sintering.