JPS60138009A - Method for operating blast furnace - Google Patents

Abstract

PURPOSE:To operate smoothly a blast furnace for a long period by charging hardly reducible ore having a specified rate of reduction into a place close to the wall of the furnace in the form of fine granules of a specified grain size so as to prevent hindrance to the operation. CONSTITUTION:When starting materials are charged into a blast furnace, hardly reducible ore having <=40% rate R of reduction is charged into a place close to the wall of the furnace in the form of fine granules of 3-10m/m grain size, and the furnace is operated. The rate R of reduction is calculated by the equation established by the results of a test carried out by reduction in a reducing atmosphere consisting of 30% CO and 70% N2 at 900 deg.C for 180min in accordance with JIS. In the equation, W0 is the weight of a sample before reduction, WF is the weight of the sample after reduction, Wi is the weight of a collection, A is T.Fe%, and B is FeO%.

Description

[Detailed Description of the Invention] The present invention provides a method for operating a blast furnace, in particular, a versatile method that allows smooth operation of the furnace to continue for a long period of time without hindering the operation even when using hard-to-reducible ores. We propose a unique blast furnace operation method for ore charging.

When used as a raw material for charging a blast furnace with hard-to-reducible gold ores such as brands such as Iscor, the reduction in gas utilization rate causes a lack of furnace heat, which usually necessitates operation at a higher coke ratio. Even though it is a hard-to-reducible ore, it is clear that charging fine-grained ore of -10% would have a negative effect on the ventilation inside the blast furnace, and it could not be used stably for a long period of time. For these reasons, powder generated during the raw material processing process is generally used as a raw material for sintering small ore wires, and for this purpose, it is crushed into fine powder and then beaded.

However, in the case of hard-to-reducible ores, even if they are crushed and used for sintering, the reducibility of the sintered ore will be affected.
It worsens the so-called low-temperature reduction powdering properties. Therefore, the coke consumption rate of sintered ore had to be increased. Figure 1 shows the correlation between the mixing ratio of Iscor, which is a difficult-to-reducible ore, in the sintering raw material and the coke consumption rate. In other words, if Iscor'il is used, the coke consumption rate is 0. 'lkQ/ is increased.

Therefore, increasing the proportion of isscol in the sintered ore increases the cost.

In the case of hard-to-reducible ores, if the lumps are used as a single brand, the gas utilization rate will decrease and the furnace heat will be insufficient, and even if the powder is used for sintering, the coke consumption rate of sintering will increase. The main purpose of this paper is to focus on these problems and propose a new blast furnace operation method for the use of refractory ores that is effective in eliminating these problems. The configuration is detailed below.

The structure of the method of the present invention is basically that, among the raw materials charged in the blast furnace, refractory ores with a reduction rate of 40 cm or less are made into fine particles of 3 to 10 m/In and loaded near the furnace wall. This method involves entering the furnace and operating the furnace. In short, in the case of difficult-to-reducible ores, there is no reduction in reducibility if the particles are -10 sized, and even if small-grain ores are charged only near the furnace wall, they can be charged smoothly without impeding air permeability. This work was completed based on the inventors' new knowledge that the furnace can be operated in a variety of ways.

Figure 2 shows the reducing properties of each brand (sintered ore, ammanite, iscol ore, and newman ore). , in the case of lumps (> 10 m/In), the reduction time isomin, but the reduction rate (R) is less than 40%, but when it becomes small particles of 3 to 101A,
The reduction rate shows the same characteristics as sintered ore powder.

Therefore, in the case of hard-to-reducible ores, it can be seen that if they are charged into the blast furnace in the form of small particles, the decrease in gas utilization rate, which has been a concern in the past, can be avoided.

In the present invention, the return rate (R) is defined as
Co: ao%, N: 70 cm, the value calculated by the following formula from the test results when 180 m1n was reduced in a reducing atmosphere at 900°C.

In the formula, Wo: R original sample weight WF: sample weight after reduction Wi: collected weight A: 'r, ire% B: Fe! O% However, if small-sized ores are charged as they are into a blast furnace without any modification, even if the reducing properties are good, it is thought that the permeability will be inhibited.

In contrast, in the case of the present invention, it has been found that the above-mentioned problem can be avoided by charging small particles of such difficult-to-reducible ore only near the furnace wall and making the particle size uniform in this area. . That is, Fig. 8 (a).

(b) This shows the in-furnace particle size distribution of sintered ore with approximately 9.6 tons of -5 mA powder added to the furnace wall and of normally charged sintered ore. It can be seen that the grain size is coarse at the center (Point No. 4) and fine near the furnace wall (Point +2).As can be seen from Figure 4, in the case of only sintered ore and in the case of added sintered ore powder. Looking at the porosity, there is a noticeable difference between the two at the center of the furnace, but there is no difference between the two at the point 1°2 position near the furnace wall. It can be seen that the ventilation resistance does not deteriorate even if the

Therefore, as mentioned above, for difficult-to-reducible ores with a reduction rate R of 40 or less, such as Iscol ore or amman ore, it is recommended to make them into small particles and charge them at a selected position near the furnace wall. The blast furnace can be operated stably over a long period of time without any disturbance.

In addition, the particle size of the above-mentioned hard-to-reducible ore is as shown in FIG.

B, lump ore), especially among fine ores, 10~
Choose one that is 8 mm in size. If the upper limit is 16 mm, if the size is larger than this, the reducing property will be poor, and the lower limit is 8 mm, and the sieving rate is limited from the point of view of efficiency.

An operational example of the present invention will be described below with reference to FIG. 6.7.

An example will be shown in which Iscol ore is used as a hard-to-reducible ore and applied to a blast furnace equipped with a bell armor type distribution control device.

The charging method is shown in Figure 6. In the conventional operation example, when charging coke, the armor position is set to 0 (co), and when charging ore, the armor position is set to 8 (08), 0oO8. On the other hand, in the charging method of the present invention, small pieces of Iscor with a size of 10 to 8 mm are charged near the furnace wall.
5th is OI, and the remaining 925% is 10 to 8 pieces of Iscor fine grain OIl, which is divided into two parts, and the armor position at the time of OH charging is set to 5, and it is placed near the core. O8o'oI, with the armor position set to 2 and K closer to the furnace wall.

0 '10 I = a @ was used. By adjusting the armor in this manner, it is possible to selectively charge one small piece of iscol ore only near the furnace wall, as shown in FIG. 6(b).

FIG. 7 is a graph of typical operating factors comparing a conventional operating example and an operating example of the present invention when small-sized iscoal ore is charged based on the above-mentioned charging method. As can be seen from this figure, even when about 9% of small pieces of iscol ore of group 8 to 10 are charged, the permeability (Dp) does not deteriorate, there is no slip, and Sl, η. It is possible to operate the furnace stably for a long period of time without having a large effect even on fluctuations in zero.

As explained above, according to the present invention, by reducing the size of the grains and charging them near the furnace wall, it is no longer necessary to use difficult-to-reducible ores such as iscor ores that hinder operations, and such ores can be used. This ensures stable furnace operation over a long period of time, even in the worst case scenario.

[Brief explanation of the drawing]

Figure 1 is a graph showing the relationship between the proportion of hard-to-reducible ores and the coke consumption unit. Figure 2 is a graph showing the characteristics of the reducing properties of various brands of ore. B) is a graph showing the particle size distribution of blast furnace charge in the radial direction of the furnace. Figure 4 is a graph comparing the porosity characteristics of lump ore and mixed lump ore in the radial direction of the furnace. Figure 5 is the interior of the blast furnace. A graph showing the particle size structure of the input raw materials, Figure 6, shows the conventional method and the method of the present invention'! i-Explanatory diagram of the charging system for implementation, FIG. 7 is a diagram of each operational factor variation comparing the conventional operation example and the present invention operation example. Patent applicant: Kawasaki Steel Corporation Figure 1 Figure 2 Figure 3 (a) (b) Figure 4 is 4 1% 1 f) Shin J Figure 5 Figure 6

Claims (1)

[Claims] L Among the raw materials charged to the blast furnace, hard-to-reducible ores with a reduction rate of 40% or less are made into fine particles of 3 to 10% and charged near the furnace wall for operation. A blast furnace operating method characterized by carrying out the following. W in the notation. : Sample weight before reduction WF: Sample weight after reduction Wl: Collection weight A: T, Fe% B: Fe0% However, the test conditions are Co: 80%, N2: 70
A reducing atmosphere of %900°C and 180 minutes is used.