JPH02294418A - Manufacture of charging material in blast furnace - Google Patents

Abstract

PURPOSE:To stabilize furnace condition and to improve the productivity of the blast furnace by using material applying fine powdery iron ore and lime stone at the specific ratio with using cement as binder on outer circumference of lump coke for blast furnace as charging material for blast furnace. CONSTITUTION:As the charging material in the case of producing molten iron in the blast furnace, raw material coating layer and kneading mixing 100 parts of the iron ore powder having <=1mm grain diameter and 19-25 parts of the lime stone powder having <=1mm grain diameter with 5-10 parts of hydraulic binder of the blast furnace cement, Portland cement, etc., is applied on the whole outer circumference of the lump coke for blast furnace having 10-30mm grain size so as to come to the wt. ratio in the range of (1:1)-(4:1) to the lump coke as core and the above material is cured in the atmosphere for about one week and hardened. By using this lump raw material, control of the mixed layer of the coke and the iron ore in the furnace can be executed and the productivity under stable furnace condition is improved.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention relates to a method for producing a blast furnace charge integrated with raw material and fuel, and more specifically, the present invention relates to a method for producing a blast furnace charge integrated with raw materials and fuel. This invention relates to a method for granulating and depositing a cold bond coating mainly composed of fine iron ore.

(Prior technology) Currently, the raw material charged to a blast furnace for steelmaking is self-soluble sintered ore, which is made by mixing iron ore powder (fine ore) with appropriate amounts of limestone powder and coke powder. It is broadly divided into iron ore, which is mainly mixed with some lump iron ore and pellets, and metallurgical coke, which is made by carbonizing coking coal in a coke oven. As shown in the process diagram in Figure 2, sintered ore is produced by mixing and granulating the sintering raw materials, ore powder, limestone powder, and coke powder (step 1), and then sintering it in a sintering machine 2. Finally, crushing and grading (culm 3)
It can be obtained by On the other hand, metallurgical coke is obtained by crushing and mixing coking coal (step 4) in an independent system, carbonizing it in a coke oven 5, and finally crushing and sizing (step 6). The iron ore containing the obtained lump sintered ore and the lump coke are stored separately, and the appropriate pieces are cut out alternately.
The materials are charged into the blast furnace 7 in alternating layers at a constant weight ratio determined by blast furnace operating conditions.

According to this charging method, iron ore and coke descend through the blast furnace while maintaining a layered packing structure, and the iron ore is sequentially heated and reduced as it descends through the furnace, softening near the bottom of the shaft. to form a fused layer. This cohesive layer has a significantly smaller porosity than the coke layer, and almost no gas flows within the layer, so the coke layer becomes the main flow path for gas.

Therefore, the cohesive layer controls the pressure tM loss across the furnace and the gas flow within the furnace, and determines the stability and efficiency of the blast furnace. As long as layered charging is carried out, the presence of a cohesive layer is unavoidable, so controlling the shape of the cohesive zone, which is an aggregate of the molten layer, is a major challenge in blast furnace operation technology.

In contrast to the layered charging described above, the mixed charging method (in which iron ore and coke are mixed in advance and the mixture is charged into the blast furnace)
For example, JP-A-55-79810) has been proposed. According to this mixed charging method, a cohesive zone with relatively good permeability is generated, and the pressure loss across the furnace is said to be significantly reduced. However, the current rotating chute/bell type charging equipment Separation of iron ore and coke is unavoidable in the transport system up to the point where it enters the furnace, or during the falling/descending process within the furnace. This is because the grain size, density, shape, etc. of both charges are different, and it is extremely difficult to control and form a mixed layer of both charges in the furnace as intended. In order to avoid such separation of the two charges, a method has been proposed in which the raw and fuel integrated charges are bonded in advance with a binding material and charged into the blast furnace. JP-A-60-262907 proposes a method of adding a hydraulic binder such as cement to bond iron ore and coke. This method involves mixing coke, iron ore, and cement in a predetermined ratio, adding water, kneading the mixture, pouring it into a mold, and curing it in the atmosphere.

The purpose of this method is simply to provide a means for producing a bonded lump of iron ore and coke that is strong enough to withstand the impact of falling into the blast furnace, and to actively improve the properties of the iron ore and coke as a blast furnace charge. (Problems to be Solved by the Invention) The purpose of the present invention is to prevent iron ore and coke from flowing into the blast furnace even if the current rotating chute/bell type charging equipment is used. The mixed layer can be controlled and formed as intended, resulting in
The purpose of this invention is to provide a method for manufacturing blast furnace charge that can significantly improve blast furnace operating performance. Another object of the present invention is to provide a raw and fuel-integrated blast furnace charging system that can actively improve the arrangement of iron ore and coke in consideration of the reaction process within the blast furnace, and significantly improve the internal properties of the blast furnace. The goal is to provide methods for manufacturing things. (Means for Solving the Problems) The present inventors have proposed that iron ore and coke be integrated using a suitable binding material that does not adversely affect blast furnace operation, and that during the integration, iron ore and coke should be The idea was to improve the blast furnace properties of the charge by devising the arrangement between iron ore and coke in consideration of the reaction process, and as a result of various studies, we decided to use a hydraulic binder such as cement as a binder. The present invention was completed based on the knowledge that the above object can be achieved by granulating and coating the outer shell surface with fine iron ore using lump coke as a core. A coating material mainly composed of fine iron ore containing a hydraulic binder such as cement as a binder is granulated on the outer surface of the coke in an amount such that the weight ratio to the lump coke is within the range of 1:1 to 4 Ct. This is a method for manufacturing blast furnace charge, which is characterized by curing and hardening after coating. (Function) The schematic steps of the method for manufacturing blast furnace charge according to the present invention are shown in FIG.

Metallurgical lump coke for blast furnaces is produced by pulverizing and mixing coking coal (step 4) in the same way as in the conventional method, and then carbonizing it in a coke oven 5.
Obtained by crushing and sizing (Step 6). All or part of the obtained lump coke is not sent directly to the blast furnace 7,
Mixing and granulation by adding coating forming material, that is, powder mainly composed of finely divided iron ore, hydraulic binder such as cement, and water.
In step 8), the outer shell of the lump coke is coated with a layer of fine iron ore to produce a double-structure raw material and fuel integrated composite. The lump coke granulation and coating using this coating forming material in step 8 can be carried out using any granulation equipment, but it is convenient to use a pelletizer in a steelworks.

The resulting integrated composite is temporarily stored in a curing yard 9 and cured to develop strength. This curing is usually carried out for about 7 days, although it depends on the type of binder used. The fully cured integrated composite is transported as it is to the blast furnace 7 and used as blast furnace charge. Separately, sintered ore that has undergone a mixing/granulation process 1, a sintering process 2, and a crushing/sizing process 3 according to a conventional method may also be prepared and charged into the blast furnace 7.

In order to prevent the reducing gas from coming into contact with the lump coke that forms the nucleus at the early stage of the reaction process in the blast furnace, it is desirable to form a dense and strong iron ore coating by adding the minimum amount of binder necessary. However, in order to do so, the particle size of the powder mainly composed of fine iron ore, which constitutes the coating material that is granulated and coated on the outer surface of the lump coke, must be such that the average particle size is 1 m or less,
Preferably, it is about 100-1 or less. Therefore, as the fine iron ore, fine ore for producing beresoto (Peresoto Feed, P.F.) can be used.

Further, the average particle size of the lump coke is preferably about 30 to 70 m1.

The chemical composition of the coating-forming material that forms the coating of the integrated composite is not particularly limited, but when the coating-forming material iron ore layer softens and melts in the high-temperature melting zone at the bottom of the blast furnace, it High basicity materials are desirable so that they form a molten slag similar to self-fusing sinter. Therefore, an appropriate amount of limestone fine powder (MgO i such as dolomite and serpentinite)
Li may be further added) to increase the basicity of the iron ore layer to a desired value. An example of a suitable formulation of the coating forming material in the present invention is heavy! It generally contains 4 to 8 parts of hydraulic binder per 100 parts of fine iron ore, preferably 1 part of fine iron ore.
00 parts, 19 to 25 parts of limestone f'A, and 5 to 10 parts of hydraulic cement as a binder, but are not limited thereto. Furthermore, a portion of coke powder may be added.

In the present invention, the hydraulic binder that can be used as the binder is not particularly limited, and may be any of conventional self-hardening, layered hydraulic, aluminous cements, and hard-burned cement. In the granulation of the integrated composite, if the amount of coating forming material is too large relative to the lump coke core, the coating will become thick and the progress of the monomer in the blast furnace may be hindered, or the coating may be damaged by impact during the transportation process. This is not desirable for blast furnace operation as there is a risk that the particles may fall off. On the other hand, if the amount of coating forming material is too small and the coating becomes thin, some lump coke will be exposed due to variations in the granulation process of the integrated composite, and reducing gas will be removed from this area in the blast furnace. This is undesirable because a reaction with the coke occurs, resulting in uneven reduction progress and reaction deterioration of the lump coke.

When we investigated the appropriate blending amount of such coating forming material, we found that the appropriate amount of coating forming material is in the range of tri to 4:1 in terms of weight ratio to the amount of lump coke in the core, as shown in Figure 3. It turns out that it exists. The integrated composite used in the test was made of a mixture of lump coke with an average particle size of 10 to 30 g01 as a core, fine ore with a particle size of 11 g01 or less (raw material for Peresot production: Kudremuk), and limestone powder, 6 After adding % by weight of blast furnace cement and an appropriate amount of water, the outer shell surface of the lump coke was granulated and coated using, for example, a dish-type granulator, and then cured in the atmosphere for one week.

The weight ratio of the amount of coating forming material to the lump coke is O. 5:t~5
: It was varied between 1 and 2. The reaction rate of lump coke is about 200g of integrated composite, carbon dioxide to j! 12 under conditions approximating the temperature rise pattern in the blast furnace while flowing /min.
After raising the temperature to 50°C, the weight loss rate of the integrated composite due to gasification of coke was expressed. In addition, the ore coating peeling rate was determined by the ratio (g) of particles having a particle size of less than 10 mm after impacting a 20 kg sample by rotating it 200 times at 25 rpm in a 130-rotation strength testing machine with a diameter of 1.0 + W and a length of 0.5 m.

According to this result, as shown in the graph in Fig. 3, when the weight ratio of the coating forming material to the lump coke becomes smaller than 1:1, the thickness of the coating layer of the lump coke outer shell is not sufficient. The lump coke is exposed, and the reaction rate of the lump coke (ie, the sinter rate) increases rapidly. Therefore, the amount of coating forming material needs to be 1 or more in weight ratio to lump coke.

In addition, during the process of transporting the integrated composite to the blast furnace, falling 41i strikes during transfer to the helt conveyor, etc.
A part of the fine iron ore coated on the outer shell of the lump coke is peeled off from the surface of the lump coke and pulverized. This pulverization rate, that is, the ore coating peeling rate, does not pose a major problem if the amount is controlled in normal blast furnace operation, but as shown in Figure 3, the ratio of the amount of coating forming material to the amount of lump coke is Since the weight ratio increases rapidly when it exceeds 5, it is necessary to keep this weight ratio at 4 or less. The blast furnace charge manufactured by the method of the present invention as described above is
It is a raw/fuel integrated composite with lump coke as the core and the outer shell surface granulated and coated with a coating material mainly composed of fine iron ore. contact, promoting the reduction reaction. On the other hand, the lump coke, which is the core covered by the iron ore coating, is prevented from coming into contact with the reducing gas, which reduces the possibility of pulverization and reaction deterioration in the upper part of the blast furnace. In this kind of double-structured integrated composite, the iron ore layer on the surface is efficiently reduced during the process of descending inside the blast furnace, softens and melts in a high temperature zone of 1,200℃ or more, and the ore melt separates, leaving it bare. The coke particles flow and drip through the filled voids. In addition, the average particle diameter of the blast furnace charge increases to the extent that the outer shell of the lump coke is coated with an iron ore layer, which is expected to have an effective effect on reducing the total pressure drop in the furnace. Furthermore, in the method of the present invention, fine ore is used as a raw material for producing the integrated composite, but a large amount of ore with a small particle size of m s > 3, which obstructs ventilation during normal sintering, is used. Since it can be digested using the method of the invention, it can also contribute to reducing the burden on the sintering process itself and improving results. In the blast furnace charge of the present invention, a hydraulic binder such as cement is used as a binder for integrating iron ore and coke. In recent years, demands for environmental protection in the steel industry have been increasing continuously, and with the conventional hot agglomeration method, it is difficult to avoid the generation of dust and harmful gases such as SO, L, NO, and L during the production process. Therefore, it is necessary to strengthen the incidental equipment for environmental conservation. On the other hand, using a hydraulic binder such as cement as a binder makes it possible to reduce investment in ancillary equipment, which is advantageous in terms of environmental measures. Hereinafter, the effects of the blast furnace charge manufactured by the method of the present invention will be explained using Examples. For the lump coke that forms the core of the integrated soil patch composite, 10 to 30 m+ of metallurgical lump coke produced in a normal coke oven is used.
The grains were sieved and sized to a size of 500 mm. The materials used to form the coating on the outer shell surface of the lump coke include fine ore consisting of two types of beresoto feed (abbreviated as P.F.) as shown in Table 1, limestone powder, and blast furnace cement as a binder. They were mixed in the same proportions and granulated with a dish-type granulator with a diameter of 2 copper while adding water so that the finished diameter was 30 to 40 mm. Moisture during granulation is 8.0% based on solid content
, the weight ratio of coating material to lump coke weight (0/C
value) was set to 3.0. Table 1 shows the results of investigating the quality of the finished product after curing the granules for one week in the atmosphere using a method similar to the quality testing method used for ordinary self-fusing sintered ore. In the table, the drop strength is determined based on the drop strength test method for sintered ore stipulated in JIS M 8711.
+5m after repeatedly dropping from a height of 4 times onto a steel plate
is the proportion of particles in m. The reduction powdering rate and reduction rate were also measured according to the reduction powdering test method and reduction test method for sintered ore, respectively. As shown in Table 1, the quality of the obtained product is comparable to that of ordinary self-fusing sintered ore.
In fact, the reduction rate exceeded the normal 60 to 70% of sintered ore. Further, a cross-sectional photograph of the obtained product is shown in FIG. 4, and it can be seen that the coke surface is coated with fine iron ore, making it an agglomerate integrated with raw materials and fuel.

(Margin below) Table 1 50n? The sintered ore content in this small blast furnace is 85%.

Table 2 shows the results of the blast furnace test operation according to this example.
As mentioned above, the replacement rate of the integrated composite corresponds to the value when the total charge in the blast furnace (excluding auxiliary raw materials) is taken as 100. In other words, it means how much of the above-mentioned sintered ore + coke lump is replaced by the above-mentioned blast furnace charge, assuming that the total charge amount is 100. Example 1 shows an example in which the integrated composite substitution rate is 20% by weight, and Example 2 shows an example in which the substitution rate is 40% by weight.

Table 2 The O/C value of this integrated composite is 3, compared to the O/C value of 3.2 during normal bed insertion operation in an actual blast furnace. Since there was no significant difference in the ratio of input amounts, a comparison operation was conducted in which the resulting integrated composite was charged directly by replacing part of the Kiseki coke that was charged in layers in the conventional method. . The internal volume of the blast furnace used in the test operation was equipped with a normal Bell Armor type charging equipment.18 According to these results, as the replacement rate of the integrated composite increases, the total pressure..., blowing pressure... It is clear that the fluctuation index and fuel ratio are reduced and the gas utilization rate is improved, and the 11I effect of controlling the coke and ore mixed layer in the blast furnace by integrating the raw fuel is fully exerted, making blast furnace operation more stable. It can be seen that this has been achieved effectively. Furthermore, in addition to this stabilizing effect, the improvement in reducibility due to the double-layer structure leads to a reduction in the fuel ratio, contributing to improved blast furnace operating performance. (Effects of the invention) As detailed above, by applying the method according to the present invention, it becomes possible to control the coke/iron ore mixed layer in the blast furnace, further stabilizing blast furnace operation and improving blast furnace performance. It becomes possible.

Further, as a raw material for the integrated composite in the present invention, fine iron ore with a small particle size, which is sieved in large quantities from the raw material for the sinter production process, can be used. Therefore, applying the method of the present invention leads to improving the permeability of the sintering raw material layer during the sintering process, and indirectly contributes to improving the performance of sintering operations.

[Brief explanation of drawings]

Figure 1 is a schematic flow diagram of the blast furnace charge production process according to the present invention; Figure 2 is a schematic flow diagram of the same process according to the conventional method; Figure 3 is the ratio of coating material amount/lump coke of the integrated composite. A graph showing the influence of changes in lump coke reaction rate and ore coating stripping rate; and FIG. 4 is a photograph showing the particle structure of the blast furnace charge produced by the method of the present invention. 1, 8: Mixing and granulation process 2: Sintering machine 3, 6: Crushing and sizing process 4: Crushing and mixing process 5: Coke oven 7: Blast furnace 9: Curing yard

Claims (1)

[Claims] On the outer surface of the metallurgical lump coke for blast furnaces, a coating forming material mainly composed of fine iron ore containing a hydraulic binder is formed in an amount such that the weight ratio to the lump coke is within the range of 1:1 to 4:1. A method for producing a blast furnace charge, which comprises coating grains and then curing and hardening them.