JPH0621301B2 - 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). , It causes hanging of the shelf and makes the inside of the furnace unstable.
On the other hand, the sintered ore charged into the blast furnace is CO +
It is reduced by the rising gas in the furnace mainly composed of N ₂ , then melted, and the unreduced portion is directly reacted with the red hot coke and reduced while dropping inside the furnace. Therefore, the higher the reduction rate immediately before melting, the less the coke consumption, and the lower the fuel ratio in the blast furnace.

Therefore, in order to increase the reducibility of the sinter, the sintering temperature should be adjusted from the conventional 1350 to 1450 ℃ while appropriately adjusting the blending ratio of fuel such as coke powder when manufacturing the sintering furnace.
Therefore, it has been proposed and implemented to lower the FeO content in the sinter by setting the temperature to a relatively low temperature of 1200 to 1300 ° C. More specifically, increasing the amount of micropores in the sintering furnace and reducing the FeO content in magnetite and amorphous silicate, which are significantly less reducible than hematite, reduce the reducibility. Since it is advantageous in increasing the temperature, it is necessary to adjust the fuel blending ratio appropriately and then sinter at a temperature of 1200 to 1300 ℃, which is lower than the temperature at which hematite is insoluble in magnetite and oxygen, which results in many micropores and magnetite. A method of producing a sinter having a low FeO content and a good reducibility is being implemented.

[Problems to be solved by the invention]

When sintering at a low sintering temperature, there is a problem that the use of refractory iron ore is limited. The origin and mineral structure of iron ore differ depending on the brand, and when subjected to sintering treatment, some are easy to assimilate at a temperature of 1200 to 1300 ° C, and some are difficult to assimilate. For example, Australian iron ore is generally
At a temperature of 00 to 1300 ℃, it is highly assimilated, whereas iron ore from South Africa is hardly assimilated.

Due to the dispersion of resource sources, etc., in general, various brands of iron ore are mixed and used for sintering, but it is difficult to assimilate during the sintering process and burned in the form of natural ore. When a dense refractory iron ore, which tends to remain in the sinter, is added, if the sintering temperature is 1200 to 1300 ° C,
A large amount of refractory iron ore grains, which are extremely inferior in reducibility, were present in the sintered ore without being assimilated as they were, and were burned at a temperature of 1200 to 1300 ° C to prevent the decomposition of hematite. On the contrary, when it is bound, the reducibility of the sintered ore is deteriorated. Therefore, in order to obtain a sinter having good reducibility, it is necessary to limit the compounding amount of such refractory iron ore.

In order to solve such a problem, the present invention has been made for the purpose of producing a sinter having a good reducibility even if a refractory iron ore is mixed under the same sintering conditions as the conventional one. It is a thing.

[Means for solving problems]

According to the present invention, as a prescription for achieving the above-mentioned object, iron ore composed of a plurality of brands is used as a main raw material, and returning ore, an auxiliary raw material and a solid fuel are mixed to obtain a sintering raw material. The grade of refractory iron ore is selected from the brands of other iron ores, and the selected refractory iron ore is added to limestone or limestone and quick lime as a part of auxiliary materials, coke powder as a part of solid fuel, and water. When the ground blast furnace slag is mixed, the content of water granulated blast furnace slag in the mixture is adjusted to 2.5% by weight or less, and water is added to the mixture to granulate, and the granules are Characterized by blending into a mixture or granulation of brand iron ore, return ore, auxiliary raw material and solid fuel and granulating it as a sintering raw material, and supplying this sintering raw material to a sintering machine for sintering. And

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.

The inventors of the present invention have conducted various tests and researches for the above purpose, and found that the granulated blast furnace slag produced in the steel mill can be suitably used for achieving this purpose depending on the way of use. An example of the composition of the granulated blast furnace slag is shown in Table 1. As seen in this example, the granulated blast furnace slag contains a considerable amount of CaO and Al ₂ O ₃ .

In the method of the present invention, such granulated blast furnace slag is used as an additive to the sintering raw material.
The granulated blast furnace slag is mixed with the selected refractory iron ore together with limestone or limestone and quicklime as a part of auxiliary materials, and coke powder as a part of solid fuel,
Mix and granulate using equipment such as a rotating drum. In this case, the addition amount of the granulating furnace slag is up to 2.5 parts by weight with respect to 100 parts by weight of the refractory raw iron ore, limestone or a mixture of limestone and quicklime, coke powder and granulated blast furnace slag. That is, up to 2.5% by weight of this mixture is recommended. If the amount added exceeds this value, the reduction rate of the sinter will improve, but if it is too large, the amount of slag in the product sinter will increase, and when the sinter is charged into the blast furnace, the coke ratio will increase. Will increase. As shown in Examples below, a sufficient reduction rate improvement effect can be obtained by blending the amount of granulated blast furnace slag up to 2.5% by weight. When adding the granulated blast furnace slag, it is preferable to use powdery one as much as possible, preferably one having an average particle diameter of 0.5 mm or less.

In this way, refractory iron ore, limestone or limestone and quicklime, coke powder and granulated blast furnace slag are mixed in an appropriate amount, and water is added to this mixture for granulation. In the method of the present invention, the granulated product is blended with the raw material mixture of the remaining brand of iron ore (a mixture or granulated product of iron ore, return ore, auxiliary raw material and solid fuel),
The whole is granulated and used as a sintering raw material. This relationship is shown in FIG.

The system A on the right side in FIG. 1 shows a basic flow for obtaining a sintered ore from a sintering raw material composed of powdered iron ore, returning ore, an auxiliary raw material, and a solid fuel. In the present invention, this sintering is performed. Of the powdered iron ore in the raw material, the dense refractory iron ore is selected and used for the B line on the left side. As the limestone or limestone and quick lime and the solid fuel used in the B system, a part of the auxiliary raw material of the A system and a part of the solid fuel can be passed to the B system. In the B system, as described above, refractory iron ore, limestone or limestone and quick lime, coke powder and granulated blast furnace slag, and the content ratio of granulated blast furnace slag in these compounds is 2.5% by weight or less. Mix as follows, mix with equipment such as a rotating drum, and add water to granulate. Granules produced by this B system are
Mix with 4 kinds of starting materials of powdered iron ore, return ore, auxiliary materials and solid fuel, or mix with 4 kinds of starting materials, granulate and load into sintering machine To do. Here, the auxiliary raw materials of system A refer to serpentine, silica sand, limestone, and the like. The solid fuel is usually coke flour.

By such a method, it is possible to produce a sintered ore with good reducibility at a high production rate even at a sintering raw material containing a refractory iron ore at low temperatures of 1200 to 1300 ℃. it can. The reason for this is that only the refractory iron ore is selected and granulated blast furnace slag, limestone or limestone and quick lime and coke powder are mixed and granulated, and then this granulated material is mixed in all the sintering raw materials. , Granulated blast-furnace slag, limestone or limestone and quicklime and coke powder exist in the vicinity of each particle of refractory iron ore in the whole sintering raw material, and it is difficult to sinter in this state. It is considered that this is because a low melting point melt is likely to be formed around each particle of the melting point iron ore, and the refractory iron ore is assimilated into the low melting point melt. Also, as shown in Table 1, granulated blast furnace slag contains a considerable amount of Al ₂ O ₃ and CaO,
The amount of Al ₂ O ₃ dissolved in the CaO-Fe ₂ O ₃ -based melt formed by the reaction of Fe ₂ O ₃ in refractory iron ore with CaO in limestone, quick lime or granulated blast furnace slag It is considered that the amount of calcium ferrite produced can be increased by increasing the amount. Therefore, in the conventional method of sintering at 1200 to 1300 ° C, refractory iron ore with remarkably inferior reducibility that remains in the sinter in the form of natural ore with almost no assimilation Even with stones, according to the method of the present invention, calcium ferrite and fine hematite can be converted, and as a result, a sintered ore with good reducibility can be obtained.

In practicing the present invention, instead of the granulated blast furnace slag used, a powder portion generated in the rectification process at the time of slowly cooling the blast furnace slag to produce the blast furnace ballast may be used, but in this case, Since S is contained in an amount of about 1.0% by weight, it is necessary to limit the amount in use.

〔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 refractory iron ore from the powdered iron ore, and limestone in system A,
It is a mixture of granulated blast furnace slag with an average particle size of 0.5 mm or less, in which a portion of quicklime and coke powder is taken. This compound B was granulated by adding water with a rotary drum and then mixed with another raw material by a second mixer as shown in the flow chart of FIG. The blending amount of the granulated blast furnace slag in Table 2 is shown as the amount relative to all the sintering raw materials, but when converted to the amount in the B blending, it becomes 1.5 parts by weight based on 100 parts by weight of the B blending. In the conventional method and the method of the present invention, the sintering raw materials were loaded into the same sintering machine, and both were sintered under the same sintering conditions.

The obtained sintering furnace was subjected to a test in accordance with 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 in Table 3, it can be seen that according to the method of the present invention, a sinter having a reduction rate increased by 0.6% was obtained under the same production rate as in the conventional method.

Example 2 Three kinds of materials were prepared in the same manner as in Example 1 except that the blending ratio of the easily meltable Australian iron ore was decreased and the blending ratio of the refractory South African iron ore was increased. We made sintering raw materials and sinter them 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 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 this, when returning ore, auxiliary raw material and solid fuel are mixed 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 The content of granulated blast furnace slag in the mixture is not more than 2.5 wt% by mixing limestone or limestone and quicklime as a part of the above-mentioned auxiliary materials, coke powder as a part of solid fuel, and granulated blast furnace slag. Then, water is added to this to granulate, and this granulated product is blended with a mixture or granulated product of the remaining brand of iron ore, return ore, auxiliary raw material and solid fuel and granulated and fired. Sintering method of iron ore, which is used as a binding raw material, and this sintering raw material is supplied to a sintering machine and sintered.