JP3394563B2 - Method for producing sintered ore with excellent softening and melting properties - Google Patents

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 a sintered ore for producing a sintered ore having an excellent softening and melting property.

[0002]

2. Description of the Related Art Conventionally, in the manufacture of sintered ore, auxiliary raw materials such as powdered coke and powdered limestone are mixed and mixed with a sintering raw material, and the mixed raw material is granulated by a granulator, and then the sintering machine is used. It is charged and operated while maintaining good ventilation of the sintered layer. In order to improve the quality of the sinter, the particle size is adjusted to reduce 0.5 mm or less in the powder coke, which adversely affects the air permeability, and the specific particle size of the powdered limestone that plays an important role in melt formation is increased or decreased. Particle size adjustment has been carried out. However, although these means can improve the reduction powdering property and the reducibility,
It was not a means to improve the most important softening and melting property in the reaction in the lower part of the blast furnace.

For example, in Japanese Examined Patent Publication No. 63-13475, a cement coke having a particle diameter of less than 7 mm and 100% by weight is mixed with cement and water, and the mixture is stacked to form a cement hydration reaction. The coke particles are aged with hydrated hydrate until the coke particles are bonded to each other.
A method of crushing to less than 40% by weight of less than mm and using it at the time of iron ore sintering to improve the combustion efficiency of powder coke and improve the reducibility (JIS reduction rate) of the product sintered ore. It is disclosed. However, improving the reducibility of the sinter alone is not enough to significantly improve the reaction in the lower part of the blast furnace, and it is important to improve the softening and melting properties of the sinter. Not not.

In Japanese Examined Patent Publication No. 63-6616, when powdered iron ore is sintered by a lower intake type sintering machine, coarse limestone having a grain size of 10 mm or less and 0.5 mm or more is blended with other blending raw materials. Disclosed is a method for producing a sinter that delays the reaction in the sintering process of limestone to reduce the production or growth of secondary hematite and improve the reduction pulverization resistance. However, nothing is mentioned about the most important improvement of the softening and melting property in the reaction in the lower part of the blast furnace.

In Japanese Patent Application Laid-Open No. 57-192228, when powdered iron ore is sintered by a lower air intake type sintering machine, the grain size is 1 to 3 m.
By mixing limestone having m of 50% or more, limestone having a particle size of 3 to 5 mm of 10% or less, limestone having a particle size of 0.25 mm or less of 19% or less with other raw materials and sintering, skeleton rhomboid Suppresses the formation of type hematite and plate-like calcium ferrite, and increases the formation of acicular calcium ferrite with good reducibility and mottled hematite with good resistance to reduction pulverization, improving reduction pulverization resistance and reducibility A method of producing a sintered ore is disclosed. However, nothing is mentioned about the most important improvement of the softening and melting property in the reaction in the lower part of the blast furnace.

Japanese Patent Laid-Open No. 61-34119 discloses a method in which limestone is added to finely powdered ore together with other compounding raw materials and sintered, and particles of limestone having a particle size of 3 to 5 mm account for 35 wt% or more of the total amount of limestone. Sintering that improves the ventilation resistance of the sintered layer, shortens the high-temperature holding time of the heat pattern, suppresses the adjacency between calcium ferrite and reoxidized hematite, and significantly improves the resistance to reduction pulverization. A method of making ore is disclosed. The publication describes that the drop strength and the reducibility are equivalent to those of the conventional sintering method, but does not describe the most important improvement in the softening and melting property in the reaction in the lower part of the blast furnace.

In Japanese Patent Laid-Open No. 58-91132, when powdered ore is sintered by a lower air intake type sintering machine, limestone has a water content of 2%.
Granulate at ~ 7% and the particle size after granulation is 0.5 mm or less is 20
% Or less and 3 mm or more and 40% or less of limestone is mixed with other raw materials and sintered to produce a large amount of calcium ferrite having good reducibility while suppressing the formation of secondary hematite having poor reduction powderability. JIS reduction rate and reduction dusting index (RDI)
There is disclosed a method for producing a sintered ore aiming at improvement of the temperature. However, no mention is made of improvement in softening and melting properties.

ISIJ International,
31 (1991) 5, p. 468 describes that macro pores are easily generated in the sintered ore after the limestone having a particle size of 0.7 mm or more and the powder coke having a particle size of 0.5 mm or more disappear in the sintering process. However, nothing is mentioned about improvement of softening and melting properties.

Materials and Processes, 4 (1991), p. 1
It is described in 126 that if a high FeO raw material such as scale is mixed in an amount of 5 wt% or more, a low-melting point silicate slag is easily generated. However, there is no description about means other than high FeO raw material content, and there is no description about the relationship between reduction of fine coke and increase of silicate slag formation and improvement of softening and melting properties.

[0010]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method for producing sinter having excellent softening and melting properties, for which no means for controlling it has been established.

[0011]

The gist of the present invention is as follows.

(1) Before charging into the sintering machine, the coke to be mixed in the sintering raw material has a particle size of 0.5 mm or less,
Super ~ 25wt%, 5.0 ~ 10.0mm coarse particles over 0 ~
Adjust the particle size of limestone to be mixed in the sintering raw material so that it becomes 10 wt%, and the fine powder having a particle size of 1.0 mm or less exceeds 0 to 30 wt.
%, 5.0 to 10.0 mm of coarse particles are adjusted to more than 0 to 20 wt%, and then the whole compounded raw material is mixed and granulated and then fired by a sintering machine to bond silicate slag and magnetite. A method for producing a sinter having excellent softening and melting properties, which comprises producing a sinter having a texture in which macropores of 50 μm or more are dispersed.

(2) In the sintering raw material before charging into the sintering machine
0.5mm particle size of return ores or sinter sieve under powder blended into
The method for producing a sintered ore according to the above (1), characterized in that the following fine powders are adjusted to be more than 0 to 5 wt%.

[0014]

In order to solve the above-mentioned problems, the present invention adjusts the particle size distribution of powdered coke, powdered limestone, return ore, and sintered ore powder to be mixed with the sintering raw material before firing, thereby forming macropores and viscosity. A sinter having excellent softening and melting properties can be obtained by securing a large number of macropores in the sinter by a combination of silicate slag formation with a high temperature.

In the present invention, first, the powder coke having a diameter of 0.5 mm or less is used.
By significantly reducing the fine powder below, the amount of powder coke buried in the powder adhering to the pseudo particles is reduced, and the flammability is greatly improved.
The amount of burned powder coke per unit time is increased to reduce the oxygen partial pressure (Po ₂ ) in the sintered layer. Then, as shown in FIG. 2 , the CaO—SiO ₂ —FeO-based low-melting silicate slag is promoted to increase the melt amount, and conversely, the CaO—SiO ₂ —Fe ₂ O ₃ -based CaO—SiO ₂ —Fe ₂ O ₃ -based alloy shown in FIG. The formation of this calcium ferrite melt is suppressed.

In addition to that, the limestone of 1.0 mm or less
Since the fine powder is greatly reduced to suppress the reactivity of limestone, the limestone reacts with the generated highly viscous silicate slag, and macropores (50 μm or more) are formed after the reaction and disappearance of the limestone. Naturally , macropores are formed even after coke burns and disappears. Silicate slag hardly penetrate into the pores since the viscosity is high, it is also less likely to block the pores themselves, the macro pores to the entire sintered ore, good
More preferably , it can be made uniformly.

By combining the method of reducing the fine powder of coke powder of 0.5 mm or less with the method of reducing the fine powder of powder limestone of 1.0 mm or less, the sintered ore has macropores mainly in the silicate slag bonding unlike the conventional one. For the whole sinter,
It is preferably uniformly distributed, and when the temperature is raised and reduced in the blast furnace, the gas sufficiently penetrates into the pores that are not clogged, so that the reduction is significantly promoted. In addition, since silicate slag and magnetite are the main constituents and part of them is a hematite-bonded structure, there is little pulverization at the time of reduction, which is often found in the connective structure where calcium ferrite and hematite are the main constituents. That is, the reduction powder resistance is good and the macro pores are burnt.
Since it is preferably uniformly dispersed throughout the sinter , JI
It becomes a sintered ore with an improved S reduction rate. Even if this sinter goes down to the softening and fusion zone under the blast furnace shaft, macro pores do not collapse, further promoting reduction, and the separation of metal and slag also shifts to a higher temperature side and becomes smoother. as shown in FIG. 3, the properties of the high temperature load softening and melting test of sintered ore is to be greatly improved. Since the fine powder portion of the return or sintered ore powder contains about 10% of CaO, if the content of this portion is reduced, the production of silicate slag is further promoted and the above effect is further increased. .

Iron and Steel, 72 (1986) 4, S3,
Low temperature reducibility up to the heat preservation zone in the blast furnace (central shaft) is J
If the IS reduction rate is 62% or more, it is good. Even if the IS reduction rate is further improved, the shaft efficiency will level off, and the high-temperature reducibility after the heat preservation zone (lower part of the shaft) will be organized by the JIS reduction rate and porosity. It is described that the improvement in high temperature reducibility is small when only the JIS reduction rate is improved, and that the combination with the increase in the porosity of the sintered ore brings about a great improvement effect. From this description, it can be said that the measure for improving the softening / melting property by increasing the generation of macropores by the method of the present invention is appropriate.

According to the method of the present invention, the coke grain size is set to be more than 0 to 25 wt% for fine powder of 0.5 mm or less and 0 to 10 wt% for coarse particles of 5.0 to 10.0 mm. 25 wt% of fine coke of 0.5 mm or less in the test result
When it becomes less, the effect begins to appear, 5.0-10.0 mm
If the coarse particles of more than 10 wt%, the adverse effect of excess heat in the lower layer due to an increase in segregation in the lower layer of the sintering bed and the non-uniform distribution of pores will start to be seen in reverse. The reason for setting the particle size of the fine coke to 0.5 mm or less is that a large amount of powder coke having a size of 0.5 mm or less was buried in the adhering powder by observing the pseudo particles of the sintering raw material under a microscope. The setting of 5.0 to 10.0 mm is that the powder coke having a size of 5.0 mm or more exists by the microscopic observation of the pseudo particles, and a large amount is present in the lower layer portion in the layer disassembly study in the sintering bed layer height direction. Because it was segregated. In addition, the powder coke with the adjusted particle size is 1.0 wt% (meaning in addition to 100%) when the total of the new sintering raw materials (iron ore, sintered ore powder, and auxiliary raw materials) is 100%. % Addition, the effect began to appear, and at 7.0 wt% or more, the effect was not seen due to excessive heat.

At the same time, the particle size of limestone is set to more than 0 to 30 wt% for fine powder of 1.0 mm or less and more than 0 to 20 wt% for coarse particles of 5.0 to 10.0 mm, as in the case of powder coke. 30 w of fine powder of 1.0 mm or less
When it is less than t%, the effect of generation of macropores over the entire sintered ore begins to appear, and on the other hand, coarse particles of 5.0 to 10.0 mm conversely increase the pore diameter from around 20 wt% and the number of pores decreases. And, it begins to disperse non-uniformly. The reason for setting the particle size of the fine limestone to 1.0 mm or less is that the fine limestone of 1.0 mm or less was taken into the adhered powder by microscopic observation of pseudo particles of the sintering raw material. Since most of the coarse particles of 1 to 5 mm were in the core of the pseudo particles, it could be estimated that macropores were generated from that part. The upper limit of coarse limestone was set to 5.0 to 10.0 mm because the limestone having a size of 5.0 mm or more as a result of microscopic observation of pseudo particles was present alone, and each layer in the sintering bed layer height direction was set. This is because even in the dismantling investigation, a large amount of segregation occurs in the lower layer, which may have an adverse effect on uniform macropore formation. This powdered limestone, when the total of the new sintering raw materials is 100%, begins to be effective when added in an amount of 5.0% by weight or more.
The effect leveled off at more than wt%.

When the amount of fine powder of reclaimed ore and sintered ore powder of 0.5 mm or less is less than 5% by weight, macropore formation is further promoted by adjusting the particle size of coke powder and limestone powder. It is considered that CaO in the fine powder portion of the sintering raw material was reduced and the silicate slag formation was further promoted. The reason for setting the finely returned ore and the sintered ore powder to 0.5 mm or less is that the similarly observed ore of pseudo particles of the sintering raw material is 0.5 mm or less and the returned ore and the sintered ore powder are buried in the adhered powder. Because it was.

[0022]

[Example] The particle size of coke powder is classified into a sieving method and a granulating method.
The same method is used for powdered limestone and the same sieving method and granulation method are used. For return or sintered ore powder, the same sieving method and a granulation method different from the above two methods are used. did. The water content during granulation of powder coke was 12.5 wt%, the water content during granulation of powder limestone was 6%, and the water content during granulation of return or sintered ore powder was 4%. The water content at the time of sieving was 7% for powder coke, 3% for powder limestone, and 1% for return or sintered ore powder.

Table 1 shows the blending ratio of the raw materials used in the pot test, Table 2 shows the sieving method and granulation method of powdered coke, powdered limestone, return or sintered ore powder, and Table 3 shows each level of the pot test. Table 4 shows the particle size distribution of the powder coke, the powder limestone, and the return or sintered ore powder used in the pot test. It should be noted that a mulmelizer was used for granulating coke powder and limestone, and a disk pelletizer was used for granulating return or sintered ore powder. Table 5 shows the conditions of the high temperature load softening and melting test.

[0024]

[Table 1]

[0025]

[Table 2]

[0026]

[Table 3]

[0027]

[Table 4]

[0028]

[Table 5]

FIG. 3 shows the production rate, the product yield, and the TI of the results of the grain size adjustment pan test of coke powder / lime limestone and return or sintered ore powder.
(Cold strength, measured by JISM8712), RDI
(Reducing powderability, pig iron section method), JIS reduction rate (JISM
8713), 5 to 25 mm ratio of product, and softening / melting property (softening start / dropping end temperature, shrinkage rate at 1350 ° C.).

FIG. 4 shows an example of the result of heat pattern measurement during the sintering process, and FIG. 5 shows an example of a micrograph of the sintered ore structure. According to the method of the present invention, the heat pattern in the sintered layer tends to be uniform from the upper layer to the lower layer, which is considered to bring about the homogenization of the product sintered ore. It was also clarified that the sinter structure obtained by the method of the present invention is mainly composed of silicate slag and magnetite and partly has a connective structure of hematite.

As described above, the following points were clarified by simultaneously adjusting the particle sizes of the coke powder, the limestone powder, and the return or sintered ore powder.

(1) The air permeability of the sintering bed is greatly improved, the sintering time is shortened, and the production rate is greatly improved.

(2) The sinter structure is mainly composed of silicate slag and magnetite , and some hematite is bonded, and the melt amount is increased, so that the product yield and TI and RDI are improved. Since the macropores increase in this structure, the JIS reduction rate also improves.

(3) Macropores are preferred in the sinter structure.
Or, since it is dispersed uniformly, the softening and melting properties are significantly improved (the softening start temperature is increased, the temperature difference between the softening start and the end of melting and dropping is reduced (fusion band width is reduced), and the softening shrinkage ratio is suppressed). Furthermore, the sharpening of the heat pattern sharpens the product particle size distribution (+25 mm decrease, 5-25 mm increase). The improvement of the particle size distribution further contributes to the improvement of the reducibility in the blast furnace.

(4) In addition to adjusting the particle sizes of the powder coke and the powdered limestone, and adjusting the particle sizes of the return or sintered ore powder at the same time, a synergistic effect occurs, and the above (1), (2) and (3) Further increase.

[0036]

EFFECTS OF THE INVENTION According to the present invention, not only the cold strength of the quality of sinter ore, the reduction pulverization property, and the JIS reduction rate can be improved, but also the softening and melting property most important for the blast furnace lower reaction can be greatly improved. Greatly contributes to stable operation of the blast furnace.

[Brief description of drawings]

FIG. 1 is a phase diagram of CaO—SiO ₂ —Fe ₂ O ₃ system.

FIG. 2 is a phase diagram of a CaO—SiO ₂ —FeO system.

FIG. 3 is a view showing a pot test result in which the particle size of powder coke / limestone and return ore / sintered ore powder is adjusted.

FIG. 4 is a view showing an example of a heat pattern measurement result in a sintered layer.

FIG. 5 is a photograph showing a microstructure of a sinter.

[Explanation of symbols]

CF columnar calcium ferrite H hematite M magnetite S silicate slag

Claims (2)

(57) [Claims] 1. A fine powder having a particle size of 0.5 mm or less of coke blended in a sintering raw material before being charged into a sintering machine has a fineness of more than 0.
25 wt%, coarse particles of 5.0 to 10.0 mm are more than 0 to 10
The limestone particle size of the limestone blended in the sintering raw material is adjusted to be more than 0 to 30 wt%,
After adjusting the coarse particles of 5.0 to 10.0 mm to be more than 0 to 20 wt%, the whole compounded raw material is mixed and granulated, and then fired by a sintering machine to form a joint structure of silicate slag and magnetite. A method for producing a sinter having excellent softening and melting properties, which comprises producing a sinter having a structure in which macropores of 50 μm or more are dispersed. 2. Before charging into a sintering machine, fine powder having a particle size of 0.5 mm or less of the reclaimed or sintered ore sieve powder mixed in the sintering raw material is adjusted to more than 0 to 5 wt%. The method for producing a sinter having excellent softening and melting properties according to claim 1, wherein the sinter is produced.