JPH046771B2 - - Google Patents

Description

[Detailed description of the invention]

[Technical Field of the Invention] The present invention relates to a method for producing calcined agglomerate ore suitable as a raw material for blast furnaces or directly reduced iron. [Prior art and its problems] As a raw material for blast furnaces or raw material for direct reduction steelmaking,
Calcined agglomerate, which is made by pelletizing powdered iron ore and calcining it, is known, and its use is expanding. This calcined agglomerate ore is usually produced as follows. That is, a solvent consisting of at least one of quicklime, slaked lime, limestone, bentonite, granulated blast furnace slag, dolomite, etc. is added to powdered iron ore with a particle size of about 8 mm or less, and CaO/SiO ₂ in the calcined agglomerated ore is added to the powdered iron ore.
Add so that the value is about 1.0 to 2.5 and mix with a mixer. Then, the obtained mixture is supplied to a disk-type first granulator, water is added thereto, and the first
The mixture is granulated using a granulator, and formed into raw pellets having a particle size of, for example, about 3 to 13 mm. Next, the obtained raw pellets are supplied to a second disk-type granulator, and about 2.5 to 4.0 wt% of coke powder is added, and the raw pellets are further granulated by the second granulator. In this way, raw pellets whose surfaces are coated with coke powder are prepared. Then, the raw pellets obtained in this way are charged into an endless moving grate type kiln, and the layer of charged raw pellets is placed on the grate of the kiln, and the drying zone of the kiln is heated. Pass through the band and firing zone in sequence. In the drying zone, drying gas at a temperature of 150 to 350°C is blown into the layer of raw pellets from above to dry the raw pellets. At the ignition zone,
High-temperature combustion gas is blown into the layer of dried raw pellets from above to ignite the coke powder on the surface of the raw pellets. In the combustion zone, the hot combustion gas produced by the combustion of coke breeze is drawn downward through the bed of green pellets to heat the green pellets to the calcination temperature. The raw pellets are calcined by heating in a calcining zone into large blocks of calcined agglomerates consisting of calcined pellets bound together by at least one of calcium ferrite and slag formed on their surfaces. . The calcined agglomerates in the form of large blocks thus obtained are discharged from the downstream end of the calciner, crushed by a crusher, and then sieved by a screen. By removing the pieces of calcined agglomerate under the sieve at the end, the calcined agglomerate ore has a maximum particle size of about 50 mm in the form of a lump formed by combining a plurality of calcined pellets, and the particle size 3 ~ 3 in the form of a single calcined pellet. Calcined agglomerates of approximately 13mm are produced. The calcined agglomerate produced in the manner described above has excellent reducing properties, since it mainly contains a large amount of fine calcium ferrite and fine hematite, which have excellent reducing properties. In addition, not only when a plurality of fired pellets are combined into a lump, but also when a single fired pellet has an irregular shape, when charged into a blast furnace, Because it does not flow unevenly to the center of the blast furnace, and gaps are created between the fired agglomerated ores,
Smooth passage of reducing gas is not obstructed. Furthermore, even if it collapses due to shock during transportation,
Since the calcined agglomerate, which is in the form of a lump made up of a plurality of calcined pellets combined, is simply separated into single calcined pellets, it can be used without any problems. However, conventionally, coke powder coated on the surface of raw pellets has a particle size of 5 mm or less.
Because a relatively coarse coke powder consisting of 70wt% and the remainder having a particle size of more than 5 mm was used, the coke powder did not adhere well to the surface of the raw pellets, resulting in insufficient coke powder coating. There were some drawbacks such as unevenness and unevenness. For this reason, when raw pellets are fired in a kiln, the firing is not performed well.
As a result, the product yield of calcined agglomerate ore was less than 70%.
There was a problem with the production rate being low at less than 1.5 tons/m ² h. [Object of the Invention] In view of the above-mentioned current situation, the present invention involves adding a solvent to powdered iron ore, forming a mixture into raw pellets, coating the obtained raw pellets with coke powder,
When the green pellets are charged into an endless moving grate calcining furnace to continuously produce calcined agglomerates, the particle size and blending ratio of coke breeze used to coat the green pellets can be selected. Then,
The purpose is to easily produce calcined agglomerate ore with high product yield and production rate. [Summary of the Invention] This invention involves adding a solvent to powdered iron ore, granulating a mixture to form raw pellets, coating the obtained raw pellets with coke powder, and moving the raw pellets endlessly. In the method for producing calcined agglomerate ore, which is charged into a grate calcining furnace and continuously calcined to thereby continuously produce calcined agglomerate ore, the coke powder has a particle size of 1 mm or less with a particle size of 80 to 1 mm.
It is characterized by the use of coke powder with a composition of 100 wt% and the remainder consisting of particles with a particle size of more than 1 mm and less than 5 mm. [Structure of the Invention] Hereinafter, the method for producing calcined agglomerates of the present invention will be described in detail. The present inventors added a solvent to fine iron ore, formed the mixture into raw pellets, coated the obtained raw pellets with coke powder, and charged the raw pellets into an endless moving grate type kiln. Therefore, in order to improve the product yield and production rate of calcined agglomerate ore in the continuous production of calcined agglomerate ore, we have repeatedly investigated the coke breeze to be used. If the blending ratio of fine coke powder increases and the particle size of the coke powder used becomes relatively fine, the coke powder will more easily adhere to the surface of the raw pellets, so the coke powder will spread evenly over the surface of the raw pellets. It is expected that the raw pellets can be sufficiently coated, and as a result, the raw pellets can be fired satisfactorily in the firing furnace, thereby improving the product yield and production rate of fired agglomerate ore. Therefore, we conducted an experiment in which the particle size and blending ratio of coke breeze were varied and coated on green pellets to produce calcined agglomerate ore. Examined. As a result, if fine coke powder with a composition consisting of 80-100wt% of particles with a particle size of 1 mm or less and the remainder of particles with a particle size of more than 1 mm and 5 mm or less is used to coat raw pellets, the product yield and production rate of calcined agglomerate ore can be greatly increased. It was found that this could be improved. Figure 1 shows the particle size 5 used to coat the raw pellets.
Figure 2 is a graph showing the relationship between the blending ratio of coke powder with a particle size of 1 mm or less in coke powder with a particle size of 1 mm or less and the product yield of the obtained calcined agglomerates. It is a graph showing the relationship between the blending ratio of coke powder and the production rate of the obtained calcined agglomerates. The particle size of the iron ore powder was about 8 mm or less, the particle size of the raw pellets was about 3 to 13 mm, and the amount of coke powder added was 3.5 wt%. As shown in Figure 1, as the blending ratio of coke powder with a particle size of 1 mm or less increases, the green pellets become better coated with coke powder and are sintered better. The yield is increasing, and when the blending ratio is 80wt% or more, the product yield is as high as 75% or more. As shown in Figure 2, the production rate of calcined agglomerate increases for the same reason as the blending ratio of coke powder with a particle size of 0.1 mm or less increases, and when the blending ratio exceeds 80wt%, it increases. , the production rate is high at over 1.5 tons/m ² h. Therefore, the product yield of calcined agglomerate ore should be increased to 75% or more.
In order to increase the production rate to 1.5 tons/ ^m2・h or more,
A powder coke with a composition of 80 to 100 wt% of particles with a particle size of 1 mm or less and the balance of particles with a particle size of more than 1 mm and 5 mm or less should be used for coating the green pellets. In this invention, as described above, the particle size is 1 mm.
By using coke powder with a composition of 80 to 100 wt% of the following, and the remainder of particle size of more than 1 mm and less than 5 mm, to coat green pellets, the product yield and production rate of calcined agglomerate ore can be greatly improved. be. In this invention, the amount of coke powder coated on the raw pellets is preferably 2.5 to 4.0 wt%, as in the conventional method. This means that the amount of coke powder to be coated is
If the amount is less than 2.5 wt%, the firing efficiency of the raw pellets in the kiln cannot be increased, and the raw pellets cannot be fired into high-strength fired agglomerates in a short time. 4.0wt%
This is because if the temperature exceeds 100, the temperature of the raw pellets during firing becomes too high, and the structure of the fired agglomerates becomes too dense. In this invention, the particle size of the powdered iron ore used is preferably about 8 mm or less, as in the conventional method.
This is because fine iron ore with a particle size of more than 8 mm can be used as is without being converted into calcined agglomerate minerals, and it is iron ore fines with a particle size of 8 mm or less that needs to be converted into calcined agglomerate minerals. In this invention, the particle size of the raw pellets is preferably about 3 to 13 mm, as in the conventional method. The reason is as follows. In other words, if the particle size of the green pellets is less than 3 mm, the high-temperature combustion gas generated by the burning of coke breeze will be inhibited from smoothly passing through the layer of green pellets during baking of the green pellets in the kiln. As a result, the production rate of calcined agglomerate ore decreases. In addition, since the fired agglomerate ore in the form of a single fired pellet has a particle size of less than 3 mm, when such a small particle size of the calcined agglomerate is charged into the blast furnace, it is difficult for the reducing gas to flow smoothly. impede passage. As a result, shelving and slipping occur in the blast furnace, resulting in the problem of unstable blast furnace operation. On the other hand, if the particle size of the green pellets exceeds 13 mm, the resistance to impact becomes weak, resulting in the problem of the green pellets collapsing when they are transferred to a kiln. Furthermore, in a short firing time as in this process, heat is not transmitted to the core of the raw pellets, and high quality fired agglomerates cannot be obtained due to insufficient heat. Furthermore, since the particle size of each fired pellet of fired agglomerate ore exceeds 13 mm, when such large fired agglomerate ore is charged into a blast furnace, the reducing gas reaches the center of the fired agglomerate ore. It takes a long time to penetrate. As a result, the reducibility of the calcined agglomerate ore in the blast furnace deteriorates, and unreduced cores remain, resulting in a problem that the high temperature characteristics of the calcined agglomerate ore under load deteriorate. [Example] Fine iron ore with the particle size composition shown in Table 1 and the chemical composition shown in Table 2, and coarse iron ore with the particle size structure shown in Table 3 and the chemical composition shown in Table 4, Fine iron ore was used at a ratio of 40 wt% and coarse iron ore was used at a ratio of 60 wt%, and 2.7 wt% of quicklime having the particle size composition shown in Table 5 was added as a solvent and a binder to the mixture, and the resulting mixture was produced. By granulating, it has a particle size distribution shown in Table 6 and has a water content of 8 to 8.
It was formed into 9wt% raw pellets.

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[Table] Next, 3.5 wt % of coke powder having a composition within the scope of the present invention as shown in Table 7 was added to the raw pellets and granulated, and the raw pellets were coated with coke powder. For comparison, the raw pellets were similarly coated with coke breeze having a formulation outside the scope of this invention, also shown in Table 7.

[Table] Then, raw pellets are charged to a thickness of 400 mm onto the grate of an endless moving grate type kiln, and the raw pellets are sequentially moved through the drying zone, ignition zone, and firing zone of the kiln, and are baked into agglomerates. Fired into ore. and,
The large blocks of calcined agglomerate ore thus obtained are discharged from the downstream end of the kiln, and after being crushed by a crusher, the calcined agglomerate pieces under the sieve with a particle size of less than 3 mm are passed through a screen. In this way, calcined agglomerate in the form of a lump with a maximum particle size of about 50 mm, in which a plurality of calcined pellets are combined, and calcined agglomerate in the form of a single calcined pellet, with a particle size of about 3 to 13 mm, are produced. Ta. The product yield, production rate, reduction rate, and reduction powdering rate of the calcined agglomerate ore produced as described above were as shown in Table 8.

〔Effect of the invention〕

According to this invention, by selecting the particle size and blending ratio of the coke breeze used to coat the green pellets, it is possible to easily produce calcined agglomerate with a high product yield and production rate. .

[Brief explanation of drawings]

Figure 1 shows the particle size 5 used to coat the raw pellets.
Figure 2 is a graph showing the relationship between the blending ratio of coke powder with a particle size of 1 mm or less in coke powder with a particle size of 1 mm or less and the product yield of the obtained calcined agglomerates. It is a graph showing the relationship between the blending ratio of coke powder and the production rate of the obtained calcined agglomerates.

Claims (1)

[Scope of Claims] 1 A mixture of powdered iron ore and a solvent is added and mixed to granulate to form raw pellets, the obtained raw pellets are coated with coke powder, and the raw pellets are transferred to an endless moving grate. Charged into a kiln and fired continuously, thus continuously producing fired agglomerate ore.
In the method for producing calcined agglomerate ore, the coke powder has a particle size of 1 mm or less and is
A method for producing calcined agglomerate ore, characterized by using coke powder having a composition of 100wt% and the remainder consisting of particle sizes of more than 1 mm and less than 5 mm.