JP3395554B2 - Sinter production method - Google Patents

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention contains 6 to 5 CaO components.
The present invention relates to a method for producing a sintered ore having a high reduction of pulverization resistance with a high product yield by using a large amount of iron ore having a high water content of crystallization in the production of a sintered ore containing 12% by weight.

[0002]

2. Description of the Related Art A general process for producing a sintered ore charged into a blast furnace is as follows. First, granulation is performed by a mixing granulator while adding an appropriate amount of water to a sintering raw material such as powdered iron ore, powdered coke, and limestone. The sintering raw material that has been made into pseudo particles by this granulation process is charged and filled in a pallet of a sintering machine. Then, while sucking air from the upper part to the lower part of the sintering raw material packed bed, the upper part of the packed bed is ignited and the coke powder in the raw material is sequentially burned from the upper part to sinter the sintering raw material. After firing, the pallet is tilted to take out a fired product (referred to as a sintered cake), which is crushed and cooled, and then sinter having a certain grain size or more is provided as a blast furnace charging raw material. Here, the calcined product having a particle size smaller than a certain size is returned to the sintering raw material as return ore.

Here, the sinter charged into the blast furnace contains 6 to 12% by weight of CaO component (hereinafter, "% by weight" will be simply referred to as "%") for reasons of general blast furnace operation. Sintered ore is desired. This is because if the content of CaO is less than 6%, the amount of melt generated in the sintering process is insufficient and the sintered ore becomes low in strength. Such a low-strength sinter produces a large amount of powder when subjected to stress due to unloading in the upper part of the blast furnace and deteriorates the air permeability of the blast furnace. Furthermore, blast furnace operation needs to be carried out under the condition of a basicity, that is, a constant CaO / SiO ₂ ratio, but if the CaO content is less than 6%, the SiO
_It is necessary to reduce the _two components, the amount of slag in the blast furnace decreases too much, and the de-S (sulfur) capacity in the blast furnace decreases.
Also, if the CaO content exceeds 12%, the amount of SiO ₂ contained in the blast furnace slag must be increased, so the amount of slag in the blast furnace becomes excessive, which deteriorates the air permeability in the blast furnace and reduces the productivity of the blast furnace. To do.

In recent years, since high-quality lump ores have been depleted,
Blast furnace operating methods for increasing the ratio of sintered ore to the blast furnace charging raw material (hereinafter referred to as "sintering ratio") have become common. Therefore, there is a tendency that a sinter having higher quality than before is required. However, depletion of high-quality iron ore is similar to that of lump ore in powdered iron ore, which is a raw material for sintering, and poor quality iron ore with a low water content of 5.0% or more of crystal water (hereinafter referred to as “high There is a tendency that the ratio of using "crystal water iron ore") becomes high.

When the proportion of highly crystalline hydrous iron ore in the sintering raw material becomes high, the reduction powdering property and strength of the sinter deteriorate, and when such a sinter is used in a blast furnace, the ventilation in the blast furnace becomes difficult. It causes a problem of worsening sex.

[0006] When the proportion of highly crystalline hydrous iron ore increases, the reduction powdering property and strength of the sintered ore deteriorates for the following two reasons.

[0007] In the firing stage of the sinter production process, the water of crystallization contained in the high crystal water iron ore causes a dehydration reaction due to the combustion heat of the powder coke. The volume expansion of water of crystallization accompanying this dehydration reaction causes fine pores and cracks in the iron ore, which significantly increases the reaction area of the iron ore.
The sintering reaction, which is a reaction between Fe ₂ O ₃ and the melt, is likely to proceed excessively. However, when viewed as the whole packed bed, the fluidity of the melt is deteriorated and the melt does not move to the whole packed bed, so that the sintering reaction becomes insufficient. As a result, the strength of the sintered ore and the product yield deteriorate.

The fine pores and cracks generated in the iron ore are
Since it remains in the sinter, the reducing gas and the sinter can easily come into contact with each other. As a result, the blast furnace is easily pulverized in the reducing atmosphere in the temperature range of 400 to 600 ° C., and the reducing pulverization index (RDI: 550 ° C., which is one of the current quality control items, is maintained in the reducing atmosphere for 30 minutes. After 900 rotations of the sinter in the drum, the weight ratio of the grain size is 2.83 mm or less, the Iron and Steel Institute Joint Research Group, Ironmaking Group Method) deteriorates. Conventionally, as a method to solve this, by increasing the amount of powdered coke added to the sintering raw material, the amount of heat required for the sintering reaction is supplemented, and the flowability and amount of the melt are ensured. ing. However,
In this method, there is a problem in that the increase in energy consumption and the input of an excessive amount of heat cause non-uniform firing inside the packed bed, which deteriorates the air permeability of the raw material packed bed, resulting in poor productivity.

Japanese Unexamined Patent Publication (Kokai) No. 57-79129 discloses an SiO ₂ clay material containing a trace amount of Al ₂ O ₃ in a coarse-grained limonite iron ore, which is a highly crystalline hydroiron ore, and an MgO-SiO ₂ containing clay. Disclosed is a method in which 5 to 15% of one or more of the quality substances are added and mixed and crushed, and the mixture is calcined without changing the blending amount of the powder coke. This is a method of adjusting the reaction between the limonitic iron ore and the limestone by coating the surface of the limonitic iron ore with the MgO-SiO ₂ -containing clayey substance. However, this method has the following problems.

Since the MgO-SiO ₂ -containing clayey substance is used, the amount of blast furnace slag increases due to an increase in the slag component contained in the sinter, and the sintering ratio in the blast furnace cannot be increased.

In order to coat the limonite ore with the MgO-SiO ₂ -containing clayey material, it is necessary to mix and crush them.
Therefore, limonite iron ore, which is a coarse-grained iron ore, is also crushed to some extent, and the particle size of the sintering raw material is reduced. this is,
As a result, the productivity and the yield are deteriorated due to the deterioration of the air permeability of the packed bed in the manufacturing process of the sinter.

[0012]

The object of the present invention is to provide CaO.
When producing a sinter containing 6 to 12% of components, a large amount of iron ore with a water content of crystallization of 5.0% or more is used to produce a sinter having a good reduction pulverization resistance and a high product yield. It is to provide a method of manufacturing.

[0013]

[Means for Solving the Problems] The inventors of the present invention have conducted extensive research on a method of using highly crystalline hydrous iron ore and dolomite, and blending highly crystalline hydrous iron ore and dolomite having a specific particle size composition in a predetermined ratio. Sintered ore with good reduction pulverization resistance by mixing the sintering raw material containing highly crystalline hydrous iron ore with a specific grain size composition with a mixer with a built-in stirring blade. We obtained the knowledge that can be manufactured with high product yield.

The present invention has been completed based on these findings, and its gist resides in the following method for producing a sintered ore.

In the production of a sinter having a CaO content of 6 to 12% by weight, iron ore containing 5.0% or more of water of crystallization is blended in an amount of 20% by weight or more with respect to the entire sintering raw material, and a particle size is 0.25 to 1.0 mm. Dolomite having a particle ratio of 30% or more is mixed with 0.5 to 25% with respect to all sintering raw materials, and after the mixed raw materials are mixed and granulated,
A method for producing a sintered ore that is fired.

The iron ore containing above 5.0% of crystal water is
It is desirable that particles having a particle size of 5 mm or less have a particle size of 80% or more and particles having a particle size of 1 mm or more have a particle size of 45% or more. Further, it is desirable to mix and granulate the iron ore containing 5.0% or more of water of crystallization and dolomite in advance, and then mix or mix granulate with other sintering raw materials and then calcinate. Furthermore, it is desirable that the above-mentioned mixing and granulation of the sintering raw material be performed by a mixer having a built-in stirring blade.

In the method of the present invention, "mm" representing the size of the particles means the representative diameter of the sieve mesh. For example, particle size
Particles with a size of 0.25 mm or less mean the size under the screen when the size of the screen is 0.25 mm, and particles with a size of 0.25 to 1.0 mm are those under the size of the screen with the size of 1 mm. Means the particles left on the 0.25 mm sieve.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION Sintered ore according to the present invention is produced by mixing dolomite with 20% or more of highly crystalline hydrous iron ore in the total sintering raw material and having a particle size ratio of 0.25 to 1.0 mm of 30% or more. It is carried out by mixing 0.5 to 25% with respect to all the sintering raw materials, mixing and granulating the mixed raw materials, and then firing.

Each item defined as above will be described below.

1. Crystal water content of iron ore: Fig. 1
FIG. 4 is a diagram showing a relationship between a mixing ratio of highly crystalline hydroiron ore in a sintering raw material and a yield of a sintered mineral product. This figure is publicly known, and it can be seen from this that if 20% or more of iron ore containing 5% crystallization water is used, the product yield of the sintered ore decreases. This decrease in yield is due to the following reasons.

Due to the reaction of dehydration of water of crystallization from the iron ore in the sintering process, fine pores and cracks are formed in the iron ore, the reaction area of the iron ore is remarkably increased, and Fe ₂ O ₃ in the iron ore is increased. The sintering reaction, which is a reaction of the melt, is likely to proceed excessively. However, when viewed as the whole packed bed, the fluidity of the melt is deteriorated and the melt does not move to the whole packed bed, so that the sintering reaction becomes insufficient. Therefore, in the present invention, the compounding amount of the high crystal hydrous iron ore is set to 20% or more of the total sintering raw material. Also,
It is not necessary to limit the upper limit of the blending, but it is desirable that the content of highly crystalline hydrous iron ore is 55% or less in relation to the auxiliary raw material.

In the present invention, the grain size composition of the high crystal hydrous iron ore is defined as "80% or more of particles having a particle size of 5 mm or less and having a particle size of 1 mm".
It is desirable that the above is 45% or more. "

When the sintering raw material is charged and filled in the pallet of the sintering machine, the particles having a large particle size are concentrated in the lower layer of the pallet due to the particle size segregation. Therefore, if more than 20% of particles having a particle size of 5 mm or more are contained in the high crystal hydrous iron ore, most of these particles concentrate in the lower layer of the pallet.
As a result, a large amount of melt having low fluidity is generated in this portion, which obstructs the ventilation of the packed bed and reduces productivity. Further, if the content of particles having a particle size of 1 mm or more is less than 45%, many of the particles having a small particle size are included, and the increase in the reaction area due to the generation of pores and cracks due to the dehydration reaction at the time of firing is small. No effect.

Here, as the high crystal water iron ore, SF.
Robb River, SF. Yandy Coup Dinner, SF.
Mara Mamba etc. can be mentioned.

2. About Dolomite: The inventors
The relationship between the water of crystallization in the iron ore and the melt, that is, the function of the MgO component in the sintering reaction was investigated.

FIG. 2 is a graph showing the relationship between the water content of crystallization in iron ore and the fluidity index of the melt produced in the process of producing sinter. In the figure, the iron ore containing up to 10% of water of crystallization was used, and the CaO content of the sintered ore was kept constant (CaO + MgO).
It is the result of investigating the fluidity of the melt when the components were changed and fired. From the figure, it can be seen that when the water of crystallization in the iron ore is 5% or more, the fluidity of the melt improves as the MgO content increases. This is because the MgO component suppresses the progress of the excessive sintering reaction between the Fe ₂ O ₃ component and the CaO component in the highly crystalline hydrous iron ore.

From the above, when dolomite containing CaO and MgO as the main components is used, fine pores and cracks are generated in the sintering process as in the case of highly crystalline hydroiron ore, and the reaction area increases. It was thought that the progress of the sintering reaction could be suppressed.

The blending amount of dolomite was set to 25% or less of the total sintering raw material so that the CaO component of the sinter to be produced was 6 to 12%. This is because if the content of dolomite exceeds 25%, the CaO content of the sinter exceeds 12%, which interferes with blast furnace operation.

The particle size composition of dolomite is 0.25 to 1.0 mm.
The content of 30% or more of the particles of dolomite is that when dolomite is mixed and granulated with high crystal water iron ore, the dispersibility of the dolomite in the sintering raw material is increased and excessive sintering of high crystal water iron ore is performed. This is to suppress the progress of the reaction. If the particle size is less than 0.25 mm or more than 1.0 mm, the above effect cannot be obtained. Therefore, if the particle size is 0.25 to 1.0 mm, it may be 100%. In addition, when the mixed granulation of dolomite and high crystal water iron ore is performed in a different system, dolomite can be selectively attached to the high crystal water iron ore, and the effect of suppressing the progress of the excessive sintering reaction can be achieved. Will increase.

FIG. 3 is a diagram showing a step of mixing and granulating sintering raw materials.

In the step (1), after mixing all the raw materials with a drum mixer, water is poured and granulated. In the step (1), all the raw materials are poured with a mixer having a stirring blade and mixed, and then granulated with a drum mixer. In the process of, after mixing the two raw materials of A and B with a drum mixer respectively, water is poured and granulated,
In the process of mixing each, the A-system raw materials are poured and mixed by a drum mixer, then granulated by the drum mixer, and the B-system raw materials are mixed by the drum mixer, and A and B are mixed.
In the step of injecting the raw material with a drum mixer to granulate, the raw material of system A is poured with a mixer with a stirring blade to mix, then granulated with a drum mixer, and the raw material of system B is mixed with a drum mixer. After that, in the process of pouring water to granulate and mixing each, the raw materials of system A are mixed with water by a mixer with a stirring blade, then granulated with a drum mixer, and the raw materials of system B are mixed with a drum mixer. Mix and granulate by pouring A and B raw materials with a drum mixer.

Although the process becomes more complicated than the process, the process more than the process, or the process more than the process, the product yield and the product quality are improved.

3. Regarding mixing and granulation: A mixer with a built-in stirring blade used in the method of the present invention is a mixer in which a blade for the purpose of stirring is installed in a cylindrical pan, and both the pan and the blade are rotationally moved. As a typical example, there is one called an Erich mixer (trade name). In this type of mixer, the rotation speed of the blades is 1 rpm or more, and since there is no compaction action on the material to be mixed, sufficient uniform mixing is possible. Therefore, by stirring and mixing the sintering raw materials with this type of mixer, dolomite can be uniformly dispersed in the raw materials without crushing the highly crystalline hydrous iron ore. This makes it possible to fully utilize the effect of dolomite on the high-crystal hydrous iron ore, and it is possible to manufacture a sinter having good resistance to reduction pulverization with a high yield. In addition, after mixing the sintering raw materials using a mixer with a built-in stirring blade,
Granulation may be performed using a rolling tumbling granulator (also referred to as a drum mixer).

[0034]

【Example】

(Example 1) As sintering raw materials, iron ore having the chemical composition and grain size constitution shown in Table 1 and auxiliary raw materials were prepared, and Tables 2 and 3 were used.
It was compounded in the compounding ratio shown in. The firing test was carried out by charging a sintering raw material into a cylindrical pot having an inner diameter of 300 mm, a bed height of 500 mm, and a superficial air velocity of 15.0 Nm ³ / (m ² · min). The reason why the superficial air velocity is constant is that the firing time is constant. In other words, keeping the heat pattern of the sintering process constant,
The yield and quality of sinter were evaluated. The ignition condition was 90 liters / minute of liquefied petroleum gas (LPG) for 2 minutes, and the firing was completed 90 seconds after the maximum exhaust gas temperature reached (BTP).

[0035]

[Table 1]

[0036]

[Table 2]

[0037]

[Table 3]

The mixers used for the mixing and granulation were a mixer equipped with stirring blades (Erich mixer) and a drum mixer, and their specifications are shown in Table 4.

[0039]

[Table 4]

The product yield and reduction powderability of the obtained sinter were investigated, and the results are shown in Table 5.

[0041]

[Table 5]

The following can be seen from Table 5.

In Test Nos. 3 to 8, high crystal hydrous iron ore was blended in an amount of 20 to 55% with respect to all the sintering raw materials, and dolomite having a particle size of 0.25 to 1.0 mm and a ratio of 55% was added to all the sintering raw materials. 10%, and the CaO component of the sinter is 10.0%, according to the method of the present invention. As a result, the product yield was 79.5 to 85.4% and the reduction powderability was 41.0 to 38.6.

On the other hand, the test No. 1 of the conventional example does not contain dolomite, and the product yield of the sintered ore is 77.6%.
Poor reduction powderability of 43.9%. Test No. 2 of the comparative example is the product yield
85.3% and reduction powderability 36.3% are good, but since the amount of high crystal water iron ore is as small as 10%, a large amount of high crystal water iron ore, which is an inferior iron ore with low iron grade, is used. Not a technology.

In Test Nos. 6 and 10 to 12, dolomite having a high crystallite iron ore content of 30% with respect to the total sintering raw material and a particle size of 0.25 to 1.0 mm in the ratio of 32 to 93% was used as the total sintering raw material. Against 10%
This is due to the method of the present invention in which the content of CaO in the sinter is 10.0%. From this, the product yield is 81.7-86.3%,
The reduction powderability is as good as 39.0 to 35.8%.

On the other hand, the test No. 9 of the comparative example has a particle size.
Dolomite with a ratio of 0.25 to 1.0 mm of 28% is mixed, resulting in a poor product yield of 78.6% and reduced powderability of 41.8%.

In Test Nos. 6 and 13 to 16, high-crystal hydrous iron ore was blended in an amount of 30% with respect to all the sintering raw materials, and dolomite having a particle size of 0.25 to 1.0 mm and a ratio of 55% was added to all the sintering raw materials. 0.5 to 25
%, And the CaO component of the sinter is set to 10.0 to 11.8% by the method of the present invention. From this, the product yield is 80.4-
85.5%, reduction powderability is good with 39.8-36.3%.

On the other hand, in the test No. 17 of the comparative example, since the dolomite was blended in an excessive amount of 40% with respect to all the sintering raw materials, the product yield was 85.4% and the reduction powderability was 35.7%. However, the CaO content of the sinter is 18.4%, which exceeds the proper range.

Test Nos. 4 to 8 and 10 to 16 were made of high crystal hydrous iron ore having a particle size of 5 mm or less in a ratio of 80% or more and a particle size of 1 mm or more in a ratio of 45% or more to all sintering raw materials. 20 to 55%, and dolomite having a particle size of 0.25 to 1.0 mm and a ratio of 32 to 93% is mixed with 0.5 to 25% of all the sintering raw materials.
This is due to the method of the present invention in which the aO component is 10.0 to 11.8%. As a result, the product yield was 80.4 to 86.3%, and the reduction powderability was 40.1 to 35.7%.

On the other hand, in Test No. 3, since the proportion of highly crystallized water iron ore having a particle size of 5 mm or less in a ratio of 95% or more and the particle size of 1 mm or more in a ratio of 35% or more, the product yield is high. 79.5%,
The reduction powderability is 41.0%.

Example 2 A high crystal water iron ore and a normal iron ore are divided into two systems as shown in the step of FIG. 3 and mixed and granulated, and the high crystal water iron ore is mixed with dolomite. The test was done. The blending and division of the raw materials were blending 18 and blending 19 in Table 6. The test method other than the mixed granulation method is the same as in Example 1. The test results are shown in Table 7.

[0052]

[Table 6]

[0053]

[Table 7]

Test No. 19 was obtained by mixing and granulating divided raw materials in a process using a drum mixer. Test No. 20 was to mix and granulate the divided raw material A containing high crystal water iron ore and dolomite with a drum mixer, and to mix the divided raw material B containing no high crystal water iron ore with a drum mixer, and combine both. Granulated by a drum mixer (step) by the method of the present invention. As a result, the product yields of Test Nos. 19 and 20 were 85.4 and 86.6%, respectively, and the reduction powderability was 36.7 and 35.8%, respectively.

On the other hand, Test No. 1 of the conventional example is one in which dolomite was not blended and the raw materials were mixed and granulated in a process using a drum mixer without dividing the raw materials.
o.18 is a mixture of granulated raw materials without mixing dolomite and granulated in a process using a drum mixer. From this, the product yields of test Nos. 1 and 18 are 77.6 and 78.6, respectively.
%, And reduction powderability is 43.9 and 42.8%, which are poor.

(Example 3) A test was carried out in which a sintering raw material containing highly crystalline hydrous iron ore and dolomite was mixed and granulated by a mixer having a stirring blade as shown in the step of FIG. The raw materials were compounded and divided into compound 6 in Table 2 and compound 19 in Table 6. The test method other than the granulation method is the same as in Example 1. The test results are also shown in Table 7 above.

Test No. 22 was prepared by mixing the raw materials without dividing them with a mixer having a stirring blade and then granulating them with a drum mixer (process). Test No. 23 is a divided raw material B containing no high crystalline water iron ore and dolomite after mixing the divided raw material A containing high crystalline water iron ore and dolomite with a mixer having a stirring blade and granulated with a drum mixer. Mixing and granulating with a drum mixer (process). Test No. 2
4 is divided raw material A containing high crystal water iron ore and dolomite with a mixer having a built-in stirring blade, and then granulated with a drum mixer, and divided raw material B containing high crystal water iron ore and dolomite is not mixed with a drum mixer. And the granules were mixed with each other and granulated with a drum mixer (step), both of which were produced by the method of the present invention. From now on, test N
o.22-24 product yield is 86.0-88.3%, reducing powderability is 36.3
It is as good as ~ 34.4%.

On the other hand, Test No. 21 of the conventional example is one in which dolomite was not compounded and the raw materials were not divided but mixed by a mixer having a stirring blade and then granulated by a drum mixer. Therefore, the product yield is 79.1% and the reduction powderability is 4
2.4% is bad.

[0059]

EFFECTS OF THE INVENTION According to the method of the present invention, a large amount of iron ore having a high water content of crystallization, which has not been able to be used in a conventional amount, is used in a large amount, and the reduction pulverization resistance can be improved without increasing the amount of coke powder. Good blast furnace charging sinter can be produced with a high product yield. This makes it possible to sufficiently deal with the depletion of high-quality iron ore.

[Brief description of drawings]

FIG. 1 is a diagram showing a relationship between a mixing ratio of highly crystalline hydroiron ore in a sintering raw material and a yield of a sintered mineral product.

FIG. 2 is a diagram showing the relationship between the water content of crystallization in iron ore and the melt fluidity.

FIG. 3 is a diagram showing a flow of mixing and granulation of sintering raw materials used in Examples.

Claims (4)

(57) [Claims] 1. In the production of a sinter having a CaO content of 6 to 12% by weight, iron ore containing 5.0% by weight or more of water of crystallization is blended in an amount of 20% by weight or more with respect to all the sintering raw materials, and a grain size of 0.25. ~ 1.0
A method for producing a sintered ore characterized in that dolomite having a ratio of mm particles of 30% by weight or more is blended with 0.5 to 25% by weight with respect to all sintering raw materials, and the blended raw materials are mixed and granulated, followed by firing. . 2. The iron ore containing 5.0% by weight or more of water of crystallization has a proportion of particles having a particle size of 5 mm or less of 80% by weight and particles having a particle size of 1 mm or more of 45% by weight or more. The method for producing a sintered ore according to claim 1, which is characterized in that. 3. The iron ore containing 5.0% by weight or more of water of crystallization and dolomite are mixed and granulated in advance, and then mixed or mixed granulated with another sintering raw material and fired. The method for producing a sintered ore according to. 4. The sintering according to claim 3 , wherein the method of preliminarily mixing and granulating the iron ore containing 5.0% by weight or more of water of crystallization and dolomite is performed by a mixer having a built-in stirring blade. Method of producing ore.