JPH0128085B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for charging uncalcined agglomerates used in a blast furnace. A typical example of uncalcined agglomerate ore is cold bond pellets, which are produced by adding a binder and appropriate moisture to powdered ore, mainly iron ore. These cold bond pellets are spherical and have a low angle of repose similar to that of calcined pellets, so when used together with the main blast furnace charges such as sintered ore, lump ore, and calcined pellets, they concentrate in the core of the blast furnace. As a layer of cold bond pellets, it exhibits unique properties (reducing properties, high temperature properties). However, cold bond pellets are topochemically reduced in the same way as calcined pellets during the reduction process, so their reducing properties are unfavorable.This also causes deterioration of their high-temperature properties, and even when mixed with sintered ore, they are No improvement in high temperature properties can be expected. Conventionally, it has been considered to add a reducing agent to cold bond pellets, but although this method improves reducibility, it significantly deteriorates the strength during reduction and causes severe powdering in the blast furnace shaft. Therefore, it is not desirable as a blast furnace charge. Therefore, the inventors developed a method for producing uncalcined agglomerates with the aim of improving the topochemical reduction of the cold bond pellets described above and improving the distribution during charging into the blast furnace (Patent Application No. 130004/1983). No., Special Application No. 151225/1983). This method involves the production of uncalcined agglomerates by adding a binder and, if necessary, moisture to powdered ore, mainly iron ore. It is characterized by adding coke of a predetermined particle size or a solid reducing agent and molding and hardening, or by crushing the molded and hardened product into a predetermined size. The uncalcined agglomerate ore produced by this method has an angle of repose comparable to that of sintered ore, and the charging distribution is improved, and because the angle of repose is large, the filling rate in the furnace core is low, which is favorable. It can provide a good gas flow. It also has good high-temperature properties such as low reducibility, high temperature reducibility, and low shrinkage when softened under load. In using unfired agglomerate that exhibits such good properties, the inventors have made it possible to use a large amount of unfired agglomerate by clarifying the conditions for use as blast furnace charge. From the perspective of making it possible, we conducted a distribution survey during charging and investigated the properties of the mixture of sintered ore and unfired agglomerate, which are the main raw materials for blast furnaces, to ensure proper charging of unfired agglomerate ore. I found a way. This invention will be explained in detail below. The gist of this invention is to produce a non-calcined agglomerate by adding a binder and, if necessary, solid fuel and water to powdered ore, mainly iron ore, to produce a non-calcined agglomerate with a grain size of 10 mm or less. more than 10 ores
Non-calcined agglomerate ore produced by molding and hardening, and if necessary crushing, using granular ore containing ~70%, with a reduced pulverization index of 70 or less, (non-calcined agglomerate ore) A blast furnace raw material charging method characterized by mixing sintered ore with sintered ore so that weight)/{(unfired agglomerated ore weight) + (sintered ore weight)} satisfies 0.05 to 0.50 and charging the mixture into a blast furnace. It's in the entry method. The uncalcined agglomerate in this invention has a particle size of 10 mm.
In the following, ores containing 10 to 70% of 1 mm or more will be used as the main raw material, and the reason is as follows. In other words, as a result of observing temperature-programmed reduction tests of uncalcined agglomerates containing ores of various sizes at temperatures of 1,200 to 1,250°C, it was found that ores of 0.5 to 1 mm or less were treated as cement,
It reacts with the auxiliary raw materials and becomes a uniform molten structure, but
It has been found that ores larger than 1 mm remain as they are and hardly contribute to softening and shrinkage.
The reason is that the reaction between ore grains and cement occurs on the surface, and the cement composition does not diffuse into the interior of the ore.
This is thought to be due to the small amount of gangue in the ore. In addition, as a result of examining high-temperature properties by varying the amount of ore larger than 1 mm that does not react with cement, we found that
It was found that if 10% or more of the grains had a particle size of mm or more, softening properties equivalent to those of ordinary blast furnace raw materials could be obtained. Furthermore, as a result of investigating the relationship between the amount of ore grains of 1 mm or more and the crushing strength, it was found that when the ratio of ore grains of 1 mm or more exceeds 70%, the crushing strength becomes lower than the standard crushing strength and is not suitable for practical use. The reason for this is presumed to be that, while the high-temperature properties become better as the ratio of ore grains of 1 mm or more increases, the amount of fine ore decreases and the filling properties during molding deteriorate. Based on the above knowledge, in this invention, it was decided to use a non-calcined agglomerate whose main raw material is powder ore containing 10 to 70% of ore grains with a particle size of 10 mm or less and 1 mm or more. The reason why the upper limit of ore grains is set to 10 mm or less is that ores larger than 10 mm can be charged into the blast furnace as they are and do not need to be agglomerated. Further, the uncalcined agglomerated ore in the present invention is used as it is after being formed into a block and hardened, or is used after being crushed, in order to improve the angle of repose and the ventilation resistance. That is, as shown in Table 1, the angle of repose of block-shaped or uncalcined agglomerated ore obtained by crushing block-shaped ore is approximately equal to the angle of repose of coke and sintered ore, which are the main blast furnace charges. Therefore, as shown in Figure 1, the change in the angle of repose due to air blast is almost the same as that of coke and sintered ore, and as shown in Figure 2, the ore/coke at the time of charging into the blast furnace is also different from that of sintered ore. are equivalent.

[Table] The inventors investigated the distribution state in the furnace of unfired agglomerate having the above-mentioned characteristics, and found that in the case of this unfired agglomerate, charging It was found that the distribution state differed depending on the method. That is, when charging in layers, uncalcined agglomerates segregate on the blast furnace wall, but when charging in a mixed manner, almost no segregation occurs. The reason for this is thought to be that in the case of layered charging, the angles of repose of the sintered ore and the unfired agglomerated ore are slightly different, so segregation occurs due to the shape in which they are charged separately. On the other hand, when it is charged mixed with sintered ore, the difference in the angle of repose between the two is small, so it behaves like one type of ore, and no segregation occurs. Therefore, the mixed charging method is effective for this uncalcined agglomerate ore. In addition, in this invention, the reduction pulverization index of the non-calcined agglomerate ore is set to 70 or less, and the usage amount of the non-calcined agglomerate ore is calculated as (non-calcined agglomerate)/{(non-calcined agglomerate)+( The reason for limiting the range of sintered ore) to 0.05 to 0.50 is as follows. Figure 4 shows the relationship between pressure loss (temperature 1200°C) and reduction powdering index (-5 mm%), which indicates the high-temperature properties of uncalcined agglomerate ore. In other words, it can be seen that the high-temperature properties of uncalcined agglomerate ore are affected by pulverization. In the case of a blast furnace, the charged blast furnace raw material is in a packed state, and the higher the filling rate, the smaller the crushing strength required for unburned agglomerates to collapse under a certain load. That is, powdering is delayed until high temperature and high reduction rate are reached, and high temperature properties are improved. Figure 5 shows the change in the number of packed particles, and when more than 50% of uncalcined agglomerate is blended, the number of ore particles occupying a unit volume decreases, and the properties of uncalcined agglomerate become noticeable. It is estimated to be.
Figure 6 shows the investigation results of high-temperature properties when uncalcined agglomerate ore and sintered ore are mixed, but there is no difference from the results for sintered ore until the amount of uncalcined agglomerate is used up to 50%. It has good properties. Therefore, it is estimated that the maximum amount of uncalcined agglomerate to sintered ore is 50%.
The lower limit of the blending amount was set at 5% because anything less than this is meaningless as a blast furnace raw material. In addition, Figure 7 shows sintered ore/non-fired agglomerated ore at 1/1
These are the results of investigating the relationship between the reduction powdering index (-3 mm%) and the pressure loss at a temperature of 1300°C when used in a mixture at a ratio of . From this figure 7, if the reduction powdering index (-3mm%) is 70 or less, sintered ore/
It was found that even when the ratio of uncalcined agglomerated ore is 1:1, it has properties equivalent to those of sintered ore. In addition, if the reduction powdering index exceeds 70, powdering during reduction will increase and it will have an adverse effect on the blast furnace shaft, so it cannot be used. On the other hand, if the reduced pulverization index becomes small, good high-temperature properties can be obtained even if the proportion of uncalcined agglomerate is increased, but if a large amount of uncalcined agglomerate is blended, sinter tends to be unevenly distributed. Since the high-temperature properties may partially deteriorate, the blending ratio of unfired agglomerate should be
It is estimated that 50% is the limit. Next, embodiments of the invention will be described. Example: A raw material having the composition shown in Table 2 and the particle size structure shown in Table 3 was added with 2% or less of -5 mm coke powder, and after mixing with no additive and water, the diameter
The uncalcined agglomerated ores A and B, which have reduction pulverization indexes of 32 and 62, are formed into a cylindrical body of 100 mm x height 60 mm, cured for 8 days, and then crushed to a size of 10 to 15 mm. The properties of the mixture as a blast furnace charge were investigated. Table 4 shows the blending amounts of sintered ore and unfired agglomerated ore, room temperature strength index, reduction powdering index, and high temperature properties.

【table】

【table】

[Table] From Table 4, it was found that the values of the room temperature strength index, reduction powdering index, and high temperature properties were values that did not adversely affect blast furnace operation. As explained above, according to the method of this invention, uncalcined agglomerated ore exhibits the same behavior as sintered ore, so almost no segregation occurs in the furnace, and since it exhibits good high-temperature properties, It becomes possible to greatly increase the amount of agglomerated ore used, which has a great effect on reducing raw material costs and fuel consumption.

[Brief explanation of drawings]

Figure 1 is a chart showing changes in the angle of repose of unfired agglomerate ore, sintered ore and coke according to the present invention, and Figure 2 shows the ore of sintered ore and unfired agglomerate when charged into a blast furnace. /coke ratio, Figure 3 is a diagram showing the distribution state of uncalcined agglomerate ore depending on the charging method, and Figure 4 is a diagram showing the reduction powdering index (-
5mm%) and pressure drop at a temperature of 1200°C, Figure 5 is a diagram showing the relationship between uncalcined agglomerate blending ratio and ore particle solid ratio, and Figure 6 is a graph showing the relationship between uncalcined agglomerate blending ratio and ore particle solid number ratio. Fig. 7 is a chart showing the relationship between the reduction powdering index (-3 mm%) of uncalcined agglomerated ore and the pressure loss at a temperature of 1300°C.

Claims (1)

[Claims] 1. Particle size is reduced by a method of producing non-calcined agglomerates by adding a binder and, if necessary, solid fuel and moisture to powdered ore, which is mainly iron ore, and agglomerating it.
Non-calcined agglomerate ore produced by molding, hardening and, if necessary, crushing, using granular ore containing 10 to 70% of ore of 1 mm or less, with a reduced pulverization index of 70 or less. The ore is mixed with sintered ore so that (weight of unfired agglomerate ore)/{(weight of unfired agglomerate ore) + (weight of sintered ore)} satisfies 0.05 to 0.50, and charged into a blast furnace. A method of charging raw materials for a blast furnace characterized by the following.