JPH02232322A - Charging material for blast furnace and its production - Google Patents

Abstract

PURPOSE:To produce a charging material for blast furnace capable of improving a blast furnace operation record by coating the external surface of metallurgical lump coke with a mixture of specific amounts of iron ore fines and binder and then burning the resulting raw fuel compound material. CONSTITUTION:Lump coke (about 10-50mm average diameter) is used as a core and the outer core surface of this core is coated with a mixture of iron ore fines (<=1mm average diameter) and binder (quick lime, slaked lime, etc.), by which a raw fuel compound material is formed. At this time, the weight ratio of the iron ore fines to the lump coke is regulated to 1:1 to 4:1, and the blending amount of the binder is regulated so that the binder comprises about 3-6wt.% of the compound material. Subsequently, the raw fuel compound material formed as mentioned above is burned in the air at about 1200 deg.C for about 15min so as to be formed into the charging material for blast furnace. By using this charging material, the mixture layer of coke and ore in the blast furnace can be controlled, and blast furnace operation can be stabilized to a greater extent.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a blast furnace charge and a method for producing the same for improving blast furnace operating performance. (Prior technology) Currently, the charging materials supplied to a blast furnace for steelmaking are self-soluble sintered ore obtained by mixing and sintering iron ore powder with appropriate amounts of limestone powder and fine coke, and lumped iron ore. It is broadly divided into metallurgical lump coke, which is produced by carbonizing coking coal in a coke oven. Figure 1 shows a schematic flow diagram of the process for manufacturing blast furnace charge using the conventional method, which consists mainly of self-fluxing sintered ore, to which lump iron ore and lump coke are charged as appropriate. In the figure, raw iron ores (fine stone, limestone powder, coke powder) that have been blended in a predetermined amount in advance are sintered in a sintering process 2 using a sintering machine after a mixing and granulating process 1, and finally crushed and Sizing process 3
After that, it is transported to blast furnace 7 as self-fusing sintered ore. on the other hand,
A predetermined amount of coking coal is also carbonized in an independent system through a crushing and mixing step 4, followed by a carbonization step 5 in a coke oven.
Finally, through the crushing and sizing process 6, it is turned into lump coke in the blast furnace 7.
will be transported to. As mentioned above, in the blast furnace 7, these raw materials and fuels are stored separately together with some lumped iron ore, and then cut out alternately in appropriate amounts and charged alternately in layers into the blast furnace. These lump iron ore, sintered ore, and lump coke are charged into the blast furnace in alternating layers at a constant weight ratio determined by the blast furnace operating conditions. According to this conventional charging method, ore and coke descend through the blast furnace while maintaining a layered packing structure, and as the ore descends through the furnace, it is sequentially heated and reduced, softening near the bottom of the shaft. and form a fused carcass. This cohesive layer has a significantly lower porosity than the coke layer, so almost no gas flows within the layer, so the coke layer becomes the main wave path for gas. Therefore, the fusion layer controls the pressure loss throughout the furnace and the gas flow within the furnace, and determines the stability and efficiency of the blast furnace. However, as long as layered charging is carried out, the existence of a cohesive layer is unavoidable, and controlling the shape of the cohesive zone, which is an aggregate of the cohesive layers, is a major issue in blast furnace operation technology. In contrast to this layered charging method, a mixed charging method (Japanese Patent Application Laid-Open No. 5-1173) in which ore and coke are mixed and the mixture is charged into a blast furnace is proposed.
5-79810) has been proposed. According to mixed charging, a cohesive zone with relatively good permeability is formed and the total pressure drop is said to be significantly reduced. However, with the current rotating chute/bell type charging equipment, the In the transportation system of
Alternatively, separation of ore and coke during the falling and descending process in the blast furnace is unavoidable. This is because the grain size, density, shape, etc. of the ore and coke charges are different.
Is the mixed layer in the blast furnace controlled as intended? ■It is very difficult to form it. Therefore, as a way to avoid separation of both charges, it is possible to charge them by binding them together with a binder.
JP-A-60-262907 proposes a method in which a hydraulic binder such as cement is added and ore and coke are combined in advance and charged.
According to this integrated composite charging method, it is thought that the mixing and integration of ore and coke will be ensured as long as the strength of the binder is not lost, but the use of a hydraulic binder is necessary at the agglomeration stage. A curing period is required to develop strength, and a considerable amount of moisture is brought into the blast furnace with the resulting integrated composite, resulting in an uneconomic coke unit consumption of heat for moisture evaporation. be. In addition, the use of powdered silk is not envisaged since the aim is to combine the ore and coke. (Problems to be Solved by the Invention) The present invention allows a mixed layer to be formed in the blast furnace as intended even if the current rotating chute/bell type charging equipment is used, and as a result, blast furnace operation is improved. The purpose of the present invention is to provide a blast furnace charge and a method for producing the same that can sufficiently improve the performance of the blast furnace.Moreover, the present invention simply produces an agglomerate in which ore and coke are integrally combined. In addition to this, we actively improve the arrangement between ore and coke, taking into account the reaction process in the blast furnace.
Another purpose of the present invention is to provide a blast furnace charge and a method for producing the same that can improve the internal properties of the charge. (Means for Solving the Problems) Therefore, the inventor of the present invention aimed to integrate ore and coke using a suitable binder that does not adversely affect blast furnace operation, and to prevent the reaction flow in the blast furnace during integration. The arrangement between ore and coke should be taken into consideration! We came up with the idea of improving the properties of the charge inside the blast furnace by devising the following, and as a result of various investigations, we came up with the following invention. That is, the main point of the present invention is to use lump coke for metallurgy, and to surround the outer surface of the lump coke, and to
; It is a blast furnace bag consisting of a sintered body of fine iron ore in an amount of 1 to 4:1. From another aspect, the present invention is obtained by granulating and coating the outer surface of lump coke for metallurgy with fine iron ore as a binder at a weight ratio of 1:1 to 1:4 to the lump coke. This is a method for producing a charge for a blast furnace, which is characterized by firing a raw fuel composite in, for example, a rotary kiln. In a preferred embodiment of the present invention, as for the binder for integration, the structure of self-fusing sintered ore, which is currently evaluated as the most suitable blast furnace charge, is used. Calcium ferrite-based softened melt generated when the coke undergoes a sintering reaction is placed around the coke and solidified and bonded during cooling. Examples of the binder having such characteristics include quicklime, slaked lime, and cement, but the binder is not limited to a specific one as long as the object of the present invention is achieved. Furthermore, when this type of coated binder is subjected to rotary kiln sintering, the softened melt exerts a compressive force on the core coke particles, thereby achieving a stronger coating bond.

The amount of the binder to be blended is not particularly limited, but it is sufficient if it is about 3 to 6% by weight of the incorporated binder. In addition, when integrating, by adopting a double structure with lump coke as the core and a sintered wL structure on the outer shell, the reduction reaction of the sintered ore layer on the surface is promoted, and conversely, the core coke inside It is expected that the particles will be prevented from coming into contact with the gas in the furnace, thereby delaying the solution loss reaction and the reaction deterioration of coke. (Operation) Next, the present invention will be explained in more detail with reference to the accompanying drawings. FIG. 2 is a flowchart of the method for producing blast furnace charge according to the present invention.
After passing through the carbonization step 5, it is made into lump coke in the crushing and sizing step 6, but the entire amount or a part of the lump coke after the crushing and sizing step 6 is not sent directly to the blast furnace 7, but is branched and prepared separately. Mixing and granulation step 8 with a mixture consisting of powdered stone powder, coke powder, limestone powder, and binder.
A double-structure raw/fuel integrated composite is produced by granulating the coke and forming a film of the mixture on the surface shell of the lump coke. The obtained integrated composite is charged into a blast furnace through a firing process 9. The above mixing and granulation steps are carried out using, for example, a dish-type granulation device. Apart from this, sintered fibers are also prepared which have undergone mixing and granulation process 1, sintering process 2, and crushing and sizing process 3 using conventional methods.
It may also be charged into the blast furnace 7. When manufacturing the above-mentioned integrated composite, the composition and composition of the raw material mixture that forms the coating is not particularly limited, but it does not easily become powder during transportation or transfer, and it does not form a lump of core during heating and baking. It is desirable to use a mixture of fine powders with high basicity so as to prevent the combustion of coke and form a strong coating mainly composed of calcium ferrite phase after calcination. In addition, regarding the grain size of the powdered iron ore that forms the coating of the integrated composite, in order to prevent the oxidative combustion of the lump coke that becomes the core during the heating and firing process in the next firing process, the particle size of the powdered iron ore is It is desirable to use fine iron ore with a diameter of 1 steel or less. Furthermore, it is preferable to use lump coke with an average diameter of 10 to 50 mm. Next, the weight ratio of the fine iron ore coating on the outer shell to the amount of lump coke that forms the core of the integrated composite is even more important. During the transportation process, the coating may separate from I+ or the progress of reduction within the blast furnace may be hindered, both of which are unfavorable for blast furnace operation. On the other hand, even if the coating is too thin, there may be some areas where coke is exposed depending on variations in the granulation process of the integrated composite and the shape of the lump coke particles.
Oxidative combustion of coke in the rotary kiln and reaction with reducing gas in the blast furnace occur from the very beginning, resulting in uneven coke burnout, reaction deterioration, and ore reduction reactions, which are undesirable. When we investigated the normal blending amount of fine iron ore for coating, we found that, as shown in Figure 3, the appropriate amount of fine iron ore is 1:1 by weight relative to the amount of lump coke in the core.
It was found to exist in the range of 1 to 4:l. The integrated composites used here had an average diameter of 10 to 30 mm.
VW lump coke is used as a cucumber, and a mixture of fine ore with a diameter of 1lII or less (raw material for producing Peleft: Kudremukh from India), limestone powder, and quicklime is granulated and coated on the outer shell surface using a dish-type granulator. The weight ratio of the amount of fine ore to the lump coke was varied between 0.5:1 and 5:1.
The amount of quicklime binder is 4% relative to the total weight of the integrated composite.
% was added. The thus obtained integrated composite was heated in air at 1200°C for 15 minutes in a horizontal electric furnace. Ore coating peeling rate (1) is diameter 1.0I1, length 0.5+*
A 20kg sample was heated at 25rpm in a 150rpm strength testing machine.
The ratio of particles with a diameter of less than 1h+m was determined after 200 rotational impacts. According to this result, as shown in the graph in Figure 3, when the weight ratio (o/c) of fine ore to lump coke becomes smaller than 1=1, the thickness of the ore coating layer on the outer shell of lump coke increases. Because the amount of coke is not sufficient and some coke is exposed, the coke burnout rate increases rapidly. Therefore, the amount of ore covered must be at least 1 in weight ratio to lump coke. In addition, during the process of transporting the integrated composite to the blast furnace, part of the fine iron ore coating coated on the lump coke outer shell peels off from the surface of the lump coke and becomes powder due to the impact of falling from the conveyor belt, etc. do. This pulverization rate, that is, the ore coating peeling rate, is not a major problem if the amount is controlled in normal blast furnace operations, but as shown in Figure 3, the blending weight ratio of the amount of fine ore to the amount of lump coke is If it exceeds 5, it increases rapidly, so this weight ratio needs to be 4 or less. The raw/fuel integrated composite produced as described above is charged into a rotary kiln in the next firing step 9, and after being preheated and dried with exhaust gas, it is heated and fired at a maximum temperature of 1200 to 1250°C (1 to 2 hours). and is discharged outside the furnace. The integrated composite that is crystallized has a nucleated structure in which lump coke remains in the inner core part and the outer shell surface is surrounded by a strong sintered coating mainly composed of calcium ferrite phase. It becomes a composite. FIG. 4 is a schematic cross-sectional view of the thus obtained integrated composite according to the present invention, in which the core lump coke 40 is surrounded on its outer surface by a sintered body 42 of fine iron ore. .

The integrated composite obtained by the method of the present invention is charged with sinter and lump coke in the same proportion as the conventional silk combination of sinter and lump coke per unit charge. By blending these, it is possible to equivalently replace the conventional combination charging, so initially, the charging ratio of the charges according to the present invention is increased step by step, and eventually the total amount is increased. may be replaced by the above-mentioned integrated composite according to the invention.

Example Next, the effects of the present invention will be explained based on an example using an actual blast furnace. Reduction rate: JIS M8713 Table 1 shows the composition of the integrated composite according to the method of the present invention and the product award after firing in a rotary kiln, using a method comparable to the quality testing method for ordinary self-fusing sintered ore. The results of the investigation are shown below. First, the core of the integrated composite is made of 20 to 40 lug coke for metallurgy produced in a normal coke oven.
Limestone powder is added to finely divided ore consisting of two types of beleft feed (abbreviated as P.F.) as an outer shell coating, quicklime is mixed as a binder, and water is added. The pellets were granulated using a dish-type granulator with a diameter of 2 to give a final diameter of 30 to 50 ms. The moisture content at the time of granulation was 8.0% in terms of external numbers, and the weight ratio of fine ore to the weight of lump coke was 3.0.

The integrated composite granules produced in this way are rotary
It was fired in a kiln at a maximum temperature of 1200°C for 1 hour to form an integrated composite. As shown in Table 1, the quality after firing was no inferior to that of ordinary self-fusing sintered silk, and in fact, the reduction rate was 60-65% higher than that of sintered ore. The quality of the integrated composite after firing was 1 because the 0/C value during normal layered insertion operation in an actual blast furnace was 3.2.
Since the ratio between the amount of ore charged and the amount of coke charged per charge is not much different, a comparative operation was conducted using a method in which these ores and coke were directly replaced. The blast furnace used for the test operation has an internal volume +
The sintered ore content is 85% in a small blast furnace of 850 n{.

Table 2 shows the results of the blast furnace test operation using wood samples. As mentioned above, the replacement of the integrated composite corresponds to the value when the total charge in the blast furnace (excluding auxiliary raw materials) is set as 100. In Example 1, the integrated composite replacement rate is 20%. Example 2
shows an example with a placement loss rate of 40%.

According to the results, as the replacement rate of the integrated composite increases, it is obvious that the total pressure drop, blowing pressure fluctuation index and fuel ratio decrease and the gas utilization rate improves, and the raw fuel is integrated. It can be seen that the effect of controlling the coke/ore mixed layer in the blast furnace was sufficiently developed, and stabilization of blast furnace operation was achieved more effectively. Furthermore, in addition to this stabilizing effect, the improvement in unidimensionality due to the layered structure leads to a reduction in the fuel-N ratio, contributing to improvements in blast furnace operation. Although not explained in detail, as a side effect of the application of the present invention, a large amount of fine iron ore is supplied from the raw material for the sintered tji manufacturing process to the integrated composite of the method of the present invention. The air permeability of the sintered T4 layer is improved, making it possible to improve the performance of sintering operations. (Effect of the invention) As detailed above, by applying the method according to the present invention,
It becomes possible to control the coke and ore mixed layer in the blast furnace, making it possible to further stabilize blast furnace operation and improve blast furnace drifting performance.

[Brief explanation of the drawing]

Figure 1 is a schematic flow diagram of the blast furnace charge production process according to the conventional method; Figure 2 is a schematic flow diagram of the same process according to the present invention; Figure 3 is a diagram showing the fine ore coke/lump coke ratio of the integrated composite. Changes in lump coke burning rate and ore coverage? Graph showing the influence on JI juvenile rate: and FIG. 4 are schematic cross-sectional views of the integrated composite according to the present invention. l, 8: Mixing/granulation process 2: Sintering process 3, 6: Crushing/
Particle sizing process 4: Grinding/mixing process 5: Coke oven 7
: Blast furnace 9: Firing process 40: Lump coke 42: Sintered body Figure 1 Figure 2 Exhibitor Sumitomo Metal Industries Co., Ltd. Agent Patent attorney Shoichi Hirose (1 other person) Figure 3

Claims (2)

[Claims] (1) Metallurgical lump coke and surrounding its outer surface,
A blast furnace charge comprising a sintered body of fine iron ore in a weight ratio of 1:1 to 4:1 to the lump coke. (2) Fine iron ore powder is added to the outer surface of the lump coke for metallurgy together with a binder at a weight ratio of 1:1 to the lump coke.
A method for producing a blast furnace charge, which comprises firing a raw material/fuel composite obtained by granulation and coating at a ratio of 4:1.