JP3006884B2 - Sinter for iron making using pisolite iron ore as raw material and method for producing the same - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a sintered ore for blast furnace iron making using pisolite iron ore as a raw material and a method for producing the same.

(Background technology)

Sinter ore, the main raw material of the blast furnace iron making method, which is a representative of iron making,
It is generally manufactured as follows. First,
Iron ore powder of about 10 mm or less, limestone, dolomite, converter slag and other CaO-containing raw materials (referred to as CaO-based raw materials), serpentine,
Mix and granulate by adding SiO ₂ containing raw materials such as quartzite and peridotite (referred to as SiO ₂ based raw materials), carbon materials such as coke powder and anthracite, and an appropriate amount of water. The quasi-granulated blended raw material (pseudo-particles) is charged to a height of about 500 mm on a pallet of a grate-movable sintering machine, and the carbon material on the surface of the packed bed is ignited. The carbon material is burned while sucking air downward and after sintering the blended raw materials by the combustion heat generated at that time, the obtained sintered cake is crushed,
After sizing, the particles having a size of 3 to 5 mm are charged into a blast furnace as a product sintered ore. In addition, sinter of powder unsuitable as a blast furnace charging material is called returned ore, and is returned as a raw material of sinter.

To operate a blast furnace stably and efficiently, high-quality sintered ore is required, and qualities such as cold strength, reducibility, and reduction powdering resistance are strictly controlled. Further, from the viewpoint of the production cost of the sinter, there is a demand for a high yield (sinter ore / sinter cake).

Looking at the world's iron ore resources, good quality hematite ore has been depleted, and it is predicted that major mines will be dug as early as 2000 if current production continues. On the other hand, SiO ₂ classified as Pisoraito iron ore into one of iron ore is from 4.5 to 6% of the iron ore. Its representatives are Robe River in Australia and Yadi Kuzyna (Ya)
ndicoojina). The reserves of these iron ore deposits are enormous, and the low-grade parts (stripping ratio) removed for mining are low, so mining costs are low,
The feature is that the supply is stable. Therefore, if this ore can be used in a large amount, it has significant significance not only in economic effects such as cost reduction but also in effective use of resources.

However, this ore has some problems because it has a so-called fish egg-like structure in which hematite (Fe ₂ O ₃ ) particles are surrounded by goethite (Fe ₂ O ₃ · H ₂ O). That is, the decomposition of the bound water occurs in the heating process, and a large crack is selectively generated in the goethite portion. As a result, the ore becomes vulnerable first. Next, when a melt is generated by the reaction between the auxiliary raw material and the iron ore, the melt rapidly penetrates into the cracks, and large pores are generated in the melt, thereby reducing the strength of the sintered body. The yield and cold strength of the sintering operation decrease. Further, the assimilation part (the part where the melt and the ore have reacted) becomes small granular hematite particles and vitreous silicate, and the low-temperature reduction powdering resistance deteriorates. For this reason, at present, it is impossible to increase the usage of pisolite iron ore. As described above, the development of the sintering method using a large amount of pisolite iron ore is significant from the viewpoint of effective use of resources and cost reduction.

The basis of the measures against pisolite iron ore is to suppress the rapid penetration of a large amount of melt into the crack. The present inventors have proposed a method for suppressing the rapid intrusion of the melt as disclosed in Japanese Patent Application No. Hei.
A method of forming a protective layer having a special composition on the surface around an ore as in the inventions of Japanese Patent Application Nos. 184047 and 2-115730, and the invention of Japanese Patent Application Nos. 3-146481 and 3-303854. Thus, a method for forming a highly viscous melt has been clarified. However, these methods have a drawback that special auxiliary raw materials, and further, a pre-granulation equipment or a special raw material segregation charging equipment for a sintering machine are required.

Therefore, the present inventors thought that if the momentary amount of the melt existing around the pisolite iron ore could be limited to a very small amount, the infiltration of the melt could be suppressed, and a number of basic research was conducted on the conditions for that, and as a concrete measure, The method of the present invention applicable to existing sintering machines has been found.

That is, an object of the present invention is to provide a sintered ore of excellent quality using iron ore, particularly pisolite iron ore, which is inexpensive and rich in resources.

A further object of the present invention is to produce excellent quality sinter using the above iron ore without requiring special equipment.

[Configuration of the invention]

In order to achieve the above object, the present invention uses a high-grade iron ore having a pisolite iron ore and a SiO ₂ content of 1.5% by mass or less (hereinafter, all% s indicate mass%) as iron-containing raw materials other than returned ore, And iron-containing raw material containing 40-70% of pisolite iron ore is mixed with auxiliary raw material, carbonaceous material, water, etc. by sintering machine at 1200 ℃
By sintering with the above heating, in the cross section of the sinter, more than 80% of the solid portion excluding the unmelted residue of the sintering raw material other than the pisolite iron ore has a densified pisolite iron ore having a width of 10 μm. What surrounds the following fine calcium ferrite, one that has a trace of pisolite iron ore and is composed of granular hematite particles and calcium ferrite that binds the hematite particles, or a mixture of granular hematite particles and calcium ferrite Another object of the present invention is to provide a sintered ore for iron made of a mixed structure of these.

In addition, as an iron-containing raw material other than returned ore provided to the sintering means, 60% or less of high-grade iron ore having an SiO ₂ content of 1.5% or less is used as an iron ore having a mass ratio of Al ₂ O ₂ / SiO ₂ of 0.3 or less. It is also possible to substitute with stones, and it is also possible to mix the total amount of the above-mentioned pisolite iron ore, high-grade iron ore and low Al ₂ O ₃ iron ore to 80% or more.

The sintered ore obtained in this way has the same excellent yield and quality as hematite ore, which has been conventionally regarded as good quality.

 The percentages of the following chemical components are all mass%.

[Brief description of drawings]

Fig. 1 shows a single brand of iron ore with a basicity of sinter of 1.6 to 2.2.
In iron ore in a sinter produced in a pot so that
O _2% and the width 10μm or less fine calcium ferrite and slag in the sintered ore is a diagram showing the ratio of the relationship.

Fig. 2 shows the ratio of Al ₂ O ₃ / SiO ₂ in iron ore in a sintered ore produced by using a single brand of ore with SiO ₂ of 1.5% or more in a pot so that the basicity of the sintered ore is 1.6 to 2.2. FIG. 4 is a diagram showing the relationship between the ratio of fine calcium ferrite having a width of 10 μm or less and slag in sintered ore.

FIG. 3 is a view showing a microstructure of the sintered ore of the present invention.

FIG. 4 is a view showing another microstructure of the sintered ore of the present invention.

FIG. 5 is a view showing another microstructure of the sintered ore of the present invention.

FIG. 6 is a view showing a microstructure of a conventional sintered ore.

Fig. 7 shows the results of sintering pot tests of raw materials consisting of pisolite iron ore and iron ore with SiO ₂ of 1.5% or less. The ratio of pisolite iron ore in both iron ores, product yield, and JI of sinter
It is a figure which shows the relationship of S fall strength.

Fig. 8 shows the results of the sintering pot test.
In raw materials composed of iron ore with SiO ₂ of 1.5% or less, the proportion of pisolite iron ore is set to 40% or 70%.
Al ₂ O ₃ / SiO ₂ mass ratio of part of iron ore with SiO ₂ less than 1.5%
It is a figure which shows the relationship between the substitution rate, the product yield, and the JIS drop strength of sinter when the iron ore is substituted with 0.3 or less.

Fig. 9 shows the results of the sintering pot test.
In the raw material consisting of iron ore with 1.5% or less of SiO _2, the ratio of pisolite iron ore is set to 40% or 70%,
60% of iron ore with less than 1.5% of O ₂ has Al ₂ O ₃ / SiO ₂ weight ratio of 0.3
Replaced with the following iron ores, and partially replaced them with Al
FIG. 3 is a graph showing the relationship between the substitution rate, the product yield, and the JIS drop strength of sintered ore when the iron ore having a mass ratio of ₂ O ₃ / SiO ₂ larger than 0.3 is substituted.

[Best mode for carrying out the invention]

Hereinafter, the best mode for carrying out the present invention will be described in detail.

 First, the basic principle of the present invention will be described.

A feature of the method of the present invention is that an existing melt that changes from moment to moment is suppressed to a very small amount as described above. The basic principle is to promote the generation of calcium ferrite (needle or plate with a width of 10 microns or less) which starts to be formed by the reaction between solid and liquid at about 1,200 ° C during the temperature rise stage of the sintering process. This calcium ferrite is generated as soon as a high CaO / SiO ₂ melt is generated, so-called melt generation rate-determining, and the amount of the melt actually present is extremely small. The present invention seeks the properties of the ore and the formation of this calcium ferrite.

First, the present inventors have conducted single stocks sintering tests was adjusted as CaO / SiO ₂ iron ore and limestone is usually within a range of sintered ore 1.6 to 2.2, the front and rear 20mm baked ore particles The cross section was polished, and the proportion of fine calcium ferrite having a width of 10 μm or less on the cross section was quantified using an optical microscope equipped with a television camera and an image analyzer. In addition, 4% of coke powder was added to the compounding raw materials.

As a result, the formation of the fine calcium ferrite requires a high CaO / SiO ₂ melt. For this reason, the SiO ₂ % in the iron ore is reduced, or the quartz (Si
O ₂₎ and a SiO ₂ minutes of clay (SiO ₂ -Al ₂ O ₃₎ was found to be important not allowed readily soluble in the melt. Furthermore, as a result of various investigations on ores containing 0.5 to 7.6% of SiO ₂ with respect to the ease of dissolution, Al ₂ O, a component in the ore, was examined.
It was confirmed that the ratio could be adjusted by the ratio of ₃ to SiO ₂ .

FIG. 1 shows the relationship between the SiO ₂ % in iron ore and the amounts of fine calcium ferrite having a width of 10 μm or less and slag. The amount of calcium ferrite slag can be considered to correspond to the amount of melt actually present. From this result, it was suggested that 1.5% or less of SiO ₂ in the iron ore was good for forming fine calcium ferrite. Fig. 2 shows SiO _{2 in} iron ore.
About 0.5-7.6% of normal imported ore, Al in iron ore
₂ shows the relationship between the ₂ O ₃ / SiO ₂ weight ratio and the amounts of fine calcium ferrite and slag having a width of 10 μm or less. Si
The amount of fine calcium ferrite and the amount of slag that are almost the same as those of ores with O ₂ of 1.5% or less are obtained when Al ₂ O ₃ / SiO ₂ is 0.1%.
The ore containing Al ₂ O ₃ / SiO ₂ having such a value of not more than 3 can be replaced with an ore containing 1.5% or less of SiO ₂ .

Based on the above findings, CaO / SiO ₂ (basicity) of sinter
There was conducted a Pisoraito iron ore was adjusted to the normal range 1.6 to 2.2, a sintered test with multiple brands mixed raw material of SiO ₂ is 1.5% or lower SiO ₂ iron ore. In addition, 4% of coke powder was added as a solid fuel to the blended raw materials.

As a result of the test, a characteristic mineral structure different from the conventional one was obtained when the ratio of pisolite iron ore in the obtained sintered ore was 40 to 70%. The structure is shown in FIG. 3 to FIG. FIG. 6 shows a comparison of the mineral structure of the pisolite iron ore in the conventional sintered ore.

As for the coarse-grained pisolite iron ore of about 2 mm or more, unmelted pisolite iron ore is densified as shown in FIG. 3 (a), and its surroundings are fine calcium oxide of 10 μm or less as shown in FIG. 3 (b). Although it is surrounded by ferrite or has traces of the original shape of pisolite iron ore as shown in FIG. 4 (a), it is assimilated to the whole by melting, and granular hematite particles and calcium ferrite that binds the particles are formed. It was deposited (FIG. 4 (b)). In some of the sintered ore particles, the structure and the mixture were also present. As shown in Fig. 5, fine pisolite iron ore powder or intermediate particles adhering to other raw materials of about 0.5 mm or less are composed of granular hematite particles and calcium ferrite (a part of which is 20- (Growing up to 30 μm), which is almost similar to the structure of the coarse-grained pisolite iron ore shown in FIG. That is, the calcium ferrite bonding structure is the feature.

In the production of sintered ore for iron making, the pores are not closed without completely melting all the raw materials in order to maintain the permeability of the sintering bed, that is, to ensure coke combustion. Therefore, some raw materials remain unmelted. In Fig. 5, the unmelted ore was intentionally removed and photographed. In addition, since iron-containing raw materials are mixed with coke powder and MgO-containing raw materials such as serpentine having a relatively wide particle size distribution, calcium ferrite is not theoretically formed around these coarse particles. Therefore, 20 samples with a size of about 20 mm were randomly selected from one sintering experiment, and the ratio of each structure was determined for the solid parts No. 1 to 6 excluding unmelted raw materials other than pisolite iron ore in the cross section of each particle. did. Table 1 shows the results.

As is clear from Table 1, when the ratio of pisolite iron ore of Nos. 2 to 5 is in the range of 40% to 70%, the structure and the area ratio are large, and the total exceeds 80%. Note that N
The reason why the structure and the structure are increased at 30% in which the ratio of the iron ore in o.1 is small is that the added SiO ₂ -based auxiliary material increases and is easily assimilated. The reason why the structure increased when the ratio of the pisolite iron ore of No. 6 was as high as 80% was considered to be that the air permeability of the bed was hindered and the combustion was uneven.

In conventional sinter, as shown in FIG. 6 (a), large cracks are generated concentrically or from the surface to the center in the unmelted residual pisolite iron ore, and a large number of various irregular pores are formed around the center. And the thickness of the wall between the pores becomes extremely thin, resulting in an extremely brittle structure. In addition, the porous portion surrounding the residual pisolite iron ore is composed of granular hematite particles combined with glassy silicate as shown in FIG. 6 (b), and has low-temperature reduction powderability and reducibility. There are inferior features. The binder phase shown in FIGS. 3 to 5 is calcium ferrite, which is known to be excellent in low-temperature reduction powdering resistance and reducibility. In fact, the low-temperature reductive powdering index (RDI) was significantly improved to 34 ± 2 in the present invention, while it was 37 ± 3 in the conventional method.
Further, looking at the pore structure shown in FIGS. 3 to 5, the pore structure is not irregular but round, and the thickness of the wall between the pores is increased, so that the strength is high. This change in the pore structure has a close relationship with the fluidity of the melt, and the calcium ferrite-based melt has a high fluidity, and thus has a unique relationship with the formation of the calcium ferrite bonding phase.

FIG. 7 shows the results of a sintering pot test of raw materials composed of pisolite iron ore and iron ore with SiO ₂ : 1.5% or less. When the ratio of pisolite iron ore characterized by the above-mentioned calcium ferrite binder phase is 40-70%, the yield of sinter ore and the cold strength (JI
It is clear that the S drop strength) is significantly improved. The reason why the yield greatly decreases when the content of the low SiO ₂ iron ore is more than 70% is that the amount of SiO ₂ is small, so that the melt itself serving as the binder phase is reduced.

Next, the low SiO ₂ iron ore in the above-mentioned composition was changed to Al ₂ O ₃ / SiO ₂ of 0.3.
% Was carried out following the sintering tests is replaced with low Al ₂ O ₃ ore.
Since the tendency did not change when the basicity of the sinter was 1.6 to 2.2, the results in the case of 1.6 were shown in FIG. It is clear that the yield and cold strength can be maintained even if the substitution is made with low Al ₂ O ₃ ore if the substitution rate is suppressed to 60% or less. In addition, this replacement rate 60
%, The sintered ore structure was essentially the same as in FIGS. 3 to 5, and the proportion of fine calcium ferrite of several μm or less was increased.

In an actual sintering operation, a shortage may occur due to a strike at Yamamoto or the like.

Therefore, how much of the above “mixed raw material of pisolite iron ore and low SiO ₂ iron ore” and “mixed raw material of pisolite iron ore, low SiO ₂ iron ore and low Al ₂ O ₃ ore” is “Al ₂ O ₃ / SiO
FIG. 9 shows the results of a sintering test conducted to determine whether iron ore ₂ can be replaced with iron ore larger than 0.3. Since there was no significant difference in the result (trend) depending on the basicity, the basicity was 1.9.
Was shown. Also in this test, the amount of coke powder added was 4%. From FIG. 9, it was found that up to the substitution rate of 20%, the yield slightly decreased and the cold strength could be maintained.

That is, as the iron-containing raw material other than returned ore, the total amount of high-grade iron ore having a SiO ₂ content of 1.5% or less and iron ore having a mass ratio of Al ₂ O ₃ / SiO ₂ of 0.3 or less becomes 80% or more. The above composition could be obtained even if it was mixed as described above.

〔Example〕

Hereinafter, the effects of the present invention will be described with reference to examples. The mineral structure is a mixture of FIGS. 3 to 5, and it has been confirmed that the total is 80% or more.

Example 1 Table 2 shows a typical compounding raw material (mainly hematite ore) and its sintering operation result in a current actual machine. Condition A in Table 3
Is the sintering of only the pisolite iron ore, and the condition B is the case where the ratio of the pisolite iron ore in the new raw material is 30% in the blended raw materials shown in Table 2. Conditions C and D are examples of the results of the sintering operation according to the method of the present invention. In the case of a single brand of pisolite iron ore, the yield, production rate and cold strength are significantly reduced, and the yield is considerably inferior to that of Table 2 when the proportion of pisolite in the new raw material is 30%. On the other hand, as shown in the condition C and D when the SiO ₂ is blended under conditions of the present invention 1.5% or lower SiO ₂ iron ore, the current average yield shown in Table 2, production rate, equal to the cold strength Was obtained.

Example 2 Table 4 shows that the pisolite iron ore and the low SiO ₂ containing less than 1.5% SiO ₂
Some of the low SiO ₂ ore in the raw material consisting of ₂ ore Al ₂ O ₃ / SiO
₂ is a result of sintering instead of iron ore of 0.3 or less within the range of the conditions of the present invention. In this case as well, the results similar to those shown in Table 2 were obtained.

Example 3 Table 5 shows that a part of the iron ore mixed raw material of Table 4 was made of Al ₂ O ₃ / SiO _2.
The result is obtained when sintering is performed instead of iron ore larger than 0.3. In this case, the yield and production rate were slightly lower than in the case of the ordinary raw material in Table 2, but the condition A in Table 3 was not satisfied.
And the cold strength was almost the same as in Table 2.

[Industrial applicability] As described above, according to the present invention, the yield of sinter ore, the use of a large amount of pisolite iron ore, which has been a problem because the quality is reduced, as in the past, Grades can be obtained. The depletion of conventional high quality hematite ore is self-evident. The method of the present invention, which enables the use of abundant and inexpensive pisolite iron ore, can solve the resource problem,
And it can greatly contribute to cost reduction of iron.

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) C22B 1/16-1/20

Claims (5)

(57) [Claims] (1) In a cross section of a sintered ore, at least 80% by mass of a solid portion excluding an unmelted residue of a sintering raw material other than pisolite iron ore is a dense pisolite iron ore surrounded by calcium ferrite. A sintered ore for iron making, characterized by being composed of granular hematite particles having traces of pisolite iron ore and of calcium ferrite that binds the hematite particles, or a mixture thereof. 2. The sintered ore for iron making according to claim 1, wherein said sintered ore structure is mixed with a structure comprising granular hematite particles and calcium ferrite. 3. A method for producing a sintered ore for iron making, comprising sintering an iron-containing raw material such as iron ore and an auxiliary raw material, a carbonaceous material and moisture by a sintering machine, wherein pisolite is used as the iron-containing raw material other than the returned ore. A method for producing a sintered ore for iron making, characterized by using iron ore, high-grade iron ore having a SiO ₂ content of 1.5% by mass or less, and mixing 40 to 70% by mass of pisolite iron ore. 4. As an iron-containing raw material other than returned iron, 60% by mass or less of high-grade iron ore having a SiO ₂ content of 1.5% by mass or less is Al ₂ O ₃
4. The method according to claim 3, wherein iron ore having a mass ratio of / SiO ₂ of 0.3 or less is substituted. 5. Iron-containing raw materials other than returned iron, such as pisolite iron ore, high-grade iron ore having a SiO ₂ content of 1.5% by mass or less, and iron ore having a mass ratio of Al ₂ O ₃ / SiO ₂ of 0.3 or less. 8 total
5. The method for producing a sintered ore for iron making according to claim 4, wherein the compounding is performed so as to be 0% by mass or more.