JP2003049228A - Sintered ore having excellent softening and melting property - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide sintered ore which has excellent softening and melting properties. SOLUTION: The sintered ore has a sintered structure in which macropores are dispersed into a bonded structure essentially consisting of silicate slag and magnetite. Hematite can be contained in a part of the above bonded structure.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a sinter having excellent softening and melting properties.

[0002]

2. Description of the Related Art Conventionally, in the production of sintered ores, 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 burned. It is put into a binding machine 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 particle size is adjusted to increase or decrease the specific particle size of the powdered limestone that plays an important role in melt formation. Etc. have been implemented. However,
Although these methods can improve the reducing pulverization property and the reducibility, they have not been the means for improving the softening and melting property, which is most important in the reaction in the lower part of the blast furnace.

For example, in Japanese Examined Patent Publication No. 63-13475, cement and water are added to and mixed with powder coke having a particle size of less than 7 mm and 100% by weight, and the mixture is stacked and formed by a hydration reaction of cement. The coke particles are cured with the hydrated hydrate, and the stowed culture is crushed to a particle size of less than 0.5 mm to 40% by weight or less and used during the sintering of iron ore. However, a method for improving the combustion efficiency of the powder coke and improving the reducibility (JIS reduction rate) of the product sintered ore is disclosed. However, in order to significantly improve the reaction in the lower part of the blast furnace, it is not enough to improve the reducibility of the sinter, and it is important to improve the softening and melting properties of the sinter. Nothing is said about improving the softening and melting properties of ores.

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 sintered ore in which the production or growth of secondary hematite is reduced by delaying the reaction in the sintering process of limestone to 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 particles of 0.25 mm or less of 19% or less with other raw materials, and sintering,
Suppressing the formation of skeletal rhomboid hematite and plate-like calcium ferrite, and increasing the formation of acicular calcium ferrite with good reducibility and mottled hematite with good reduction pulverization resistance. A method for producing a sinter that improves reducibility 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.

JP-A-61-34119 discloses a method in which limestone is added to finely divided ores 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. To improve the ventilation of the sintered layer, shorten the high-temperature holding time of the heat pattern, suppress the adjacency of calcium ferrite and reoxidized hematite, and significantly improve the reduction pulverization resistance. A method for producing slag is disclosed. The above publication describes that the drop strength and the reducibility are equivalent to those obtained by the conventional sintering method, but nothing is mentioned about the most important improvement in the softening and melting property in the reaction in the lower part of the blast furnace. Not not.

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 2
Limestone with 0% or less, 3 mm or more and 40% or less is mixed with other raw materials and sintered to produce a large amount of calcium ferrite with good reducibility while suppressing the formation of secondary hematite that is poor in reduction powderability. JIS reduction rate and reduction pulverization index (RD
A method for producing a sintered ore for improving I) 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.

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 the most important improvement of the softening and melting property in the reaction in the lower part of the blast furnace.

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 multi-mixing, and there is no description about the relationship between the decrease of fine coke and the increase of silicate slag formation, and the most important improvement of the softening and melting property in the reaction in the lower part of the blast furnace. .

[0010]

The object of the present invention is to provide a sinter having excellent softening and melting properties (the most important properties in the reaction in the lower part of a blast furnace), which means for controlling the sinter have not been established so far. And

[0011]

The gist of the present invention is as follows.

(1) A sintered ore having an excellent softening and melting property, which has a sinter structure in which macropores are dispersed in a bond structure mainly composed of silicate slag and magnetite.

(2) A sinter having excellent softening and melting properties as described in (1) above, which further contains hematite in part of the connective structure.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION In order to solve the above-mentioned problems, the present invention relates to powdered coke, powdered limestone, reclaimed mineral, and
By adjusting the particle size distribution of the sintered ore powder before firing, the softening and melting properties obtained by securing a large number of macropores in the sintered ore by combining the formation of macropores and the formation of highly viscous silicate slag To provide an excellent sinter.

In the present invention, first, 0.5 mm of coke powder is used.
By significantly reducing the following fine powders, the amount of powder coke buried in the powder of the pseudo particles is reduced, and the combustibility is significantly improved.The combustion amount of powder coke per unit time is increased, and sintering is performed. The oxygen partial pressure (Po ₂ ) in the layer is lowered. Then, as shown in FIG. 2, CaO-SiO ₂
-FeO-based low-melting silicate slag is promoted to be produced, and the amount of melt is also increased. On the contrary, CaO-SiO shown in FIG.
Generation of a _2- Fe ₂ O ₃ -based calcium ferrite melt is suppressed.

In addition, the fine powder of limestone of 1.0 mm or less is significantly reduced to suppress the reactivity of limestone, so that the limestone reacts with the generated highly viscous silicate slag, and After reaction and disappearance, macropores (50 μm or more) are formed. Naturally, macro pores are formed even after the coke burns and disappears. Since the silicate slag has a high viscosity, it hardly penetrates into the pores and rarely blocks the pores themselves, so that the macropores can be preferably formed uniformly in the entire sintered ore.

When the method of reducing the fine powder of 0.5 mm or less of the powder coke and the method of reducing the fine powder of 1.0 mm or less of the powder limestone are combined, the structure of the sinter is different from the conventional one, and the structure of the sinter is a silicate slag bond. Macro pores in the main body,
It is preferably uniformly distributed throughout the sinter, and when the temperature is raised and reduced in the blast furnace, the gas sufficiently penetrates into the pores that are not clogged, so the reduction is significantly promoted. Moreover, since silicate slag and magnetite are the main constituents and partly the connective structure of hematite, there is little pulverization during reduction, which is often found in the connective structure of calcium ferrite and hematite. That is, the sintered ore has good reduction powdering resistance, and macro pores are preferably uniformly dispersed throughout the sintered ore, so that the JIS reduction rate is improved. Even if the sintered ore descends to the softening fusion zone under the blast furnace shaft, the macro pores do not collapse, so the reduction is further promoted, and the separation of metal and slag also shifts to the higher temperature side. And becomes smooth, Fig. 3
As shown in, the properties of the high temperature load softening and melting test of the sinter are significantly improved. Since the fine powder part of the return or sintered ore powder contains about 10% of CaO, if the content of this part is reduced, the production of silicate slag is further promoted and the above effect is further increased. become.

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

In the method of the present invention, the coke grain size is
Fine powder of 0.5 mm or less is more than 0 to 25 wt%, 5.0 to 1
The reason why the coarse particles of 0.0 mm are more than 0 to 10 wt% is the result of the pot test conducted in advance, and when the fine coke of 0.5 mm or less becomes less than 25 wt%, the effect starts to appear and 5.0
This is because, if the coarse particles of ˜10.0 mm exceed 10 wt%, the adverse effect of excessive 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 start to appear conversely.
The reason for setting the particle size of fine coke to 0.5 mm or less is that
This is because a large amount of powder coke having a size of 0.5 mm or less was buried in the adhered powder by observing the pseudo particles of the sintering raw material under a microscope. The reason why the coarse grain coke upper limit particle size setting was set to 5.0 to 10.0 mm was the same. , Pseudo-particle microscopic observation, 5.0mm
This is because the coke powder of No. 1 existed alone and was segregated in the lower part in a large amount in the layer disassembly survey in the height direction of the sintered bed layer. In addition, the powder coke with this particle size adjustment is 100% of the total of the new sintering raw materials (iron ore, sintered ore powder, and auxiliary raw materials).
Then, the outside% (meaning in addition to 100%) display is 1.
The effect began to appear from the addition of 0 wt%, and the effect was not seen due to excessive heat at 7.0 wt% or more.

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. In addition, according to the preliminary pot test result, when the fine powder of 1.0 mm or less is less than 30 wt%, the effect due to the formation of macropores over the entire sintered ore begins to appear, and 5.0 to 10.0 m
This is because the coarse particles of m, on the contrary, have a too large pore diameter from around 20 wt% and the number of pores decreases, and the particles start to be dispersed nonuniformly. Set the particle size of fine limestone to 1.0 m
The reason why the particle size was set to m or less was that microscopic particles of 1.0 mm or less were taken into the adhered powder by microscopic observation of pseudo particles of the sintering raw material. Most of the coarse particles of 1 to 5 mm were at the core of the pseudo particles, so it could be estimated that macropores were generated from that part. The upper limit of the coarse-grained limestone was set to 5.0 to 10.0 mm by microscopic observation of pseudo particles, and 5.0 mm of limestone was present alone, and
This is because even in the disassembly examination of each layer in the height direction of the sintered bed layer, a large amount of segregation occurs in the lower layer portion, which may adversely affect the formation of uniform macropores. With respect to this powdered limestone, when the total of the new sintering raw materials was 100%, the effect began to appear from the addition of 5.0 wt% or more in the content of%, and the effect leveled off when it became 15 wt% or more.

If the amount of fine powder of reclaimed ore and sintered ore powder of 0.5 mm or less is less than 5% by weight, the generation of macropores is further promoted by adjusting the particle size of coke powder and limestone powder. It is considered that the amount of CaO in the fine powder portion of the sintering raw material was reduced and the production of silicate slag was further promoted. The reason for setting the fine ore powder and the sintered ore powder to be 0.5 mm or less is the same as above.
This is because the following return ore and sintered ore powder were buried in the adhered powder.

[0022]

[Examples] The particle size of powder coke was adjusted by two methods of sieving method and granulation method, and powder limestone was also adjusted by two methods of the same sieving method and granulation method. The powder was prepared by the same sieving method and a granulation method different from the above two methods. The water content during granulation of coke powder was 12.5 wt%, the water content during granulation of powdered limestone was 6%, and the water content during granulation of return or sintered ore powder was 4%. The water content during sieving is 7 for powder coke.
%, Powdered limestone was 3%, and returned or sintered ore powder was 1%.

Table 1 shows the mixing ratio of the raw materials used in the pot test, Table 2 shows the sieving method and granulation method of powdered coke, powdered limestone, reclaimed or sintered ore powder, and Table 3 shows the pot test. Table 4 shows the levels of powdered coke and powdered limestone used in the pan test
The particle size distribution of the sintered ore powder is shown. 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 measurement result of the heat pattern during the sintering process. Then, FIG. 5 shows an example of a micrograph of a sinter structure, and FIG. 6 shows an example of a sinter structure in which macropores are dispersed. 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 (see FIG. 4), which is considered to bring about the homogenization of the product sintered ore. . Further, 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 has a partially hematite bond structure, and macropores are preferably uniformly dispersed ( (See FIGS. 5 and 6).

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 sintered ore structure is mainly composed of silicate slag and magnetite, and partly has a hematite bond structure, and since the melt amount also increases, the product yield and TI, RD
I improves. Since macro pores increase in this structure, J
The IS reduction rate is also improved.

(3) Since macropores are preferably uniformly dispersed in the sintered ore structure, the softening and melting properties are significantly improved (the softening start temperature is increased, and the temperature difference between the softening start and the melt dropping end is reduced (fusion). Bandwidth reduction), softening shrinkage suppression). 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) ) Is further increased.

[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 but also the softening and melting property most important for the reaction in the lower part of the blast furnace can be greatly improved. Therefore, it greatly contributes to the 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] Fig. 3 is a diagram showing the results of a pot test in which the particle size of powdered coke / limestone and return ore / sintered ore powder is adjusted.

FIG. 4 is a diagram showing an example of a result of measuring a heat pattern in a sintered layer.

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

FIG. 6 is a view showing a microscopic structure in which macropores of sinter are dispersed.

[Explanation of symbols]

CF: Columnar calcium ferrite H ... Hematite M ... Magnetite S ... Silicate slag

Claims (2)

[Claims] 1. A sinter having an excellent softening and melting property, which has a sinter structure in which macropores are dispersed in a bond structure mainly composed of silicate slag and magnetite. 2. The sinter according to claim 1, further comprising hematite in a part of the connective structure.