JPS6028888B2 - Pseudo-graining method for sintering raw materials - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for pseudo-granulating a sintered raw material in a drum mixer, which is a part of the sintering operation process for producing sintered ore by blending various fine ores.

In silk burning operations, the bed is kept well ventilated to efficiently burn the coke powder contained therein, while the ore particles are brought into contact with each other to allow competitive reactions to proceed sufficiently, and the bond strength is increased by the molten material. It is required that two contradictory conditions be met. In order to meet this requirement, it is necessary to perform sufficient mixing, humidity control, and granulation using a drum mixer. For this reason, the present inventors conducted experimental research and discovered the following fact.

In other words, to give an example, as shown in Figure 1, the wet raw material in the drum mixer is divided into its occupancy rate and number of fuels [Fr=Fr: fluid number N: number of revolutions (sec-1) D: drum Diameter (skin) G: Acceleration of gravity (/sec2)・
...980], and can be divided into a slip region indicated by an x mark in the figure, a normal rolling region indicated by a 0 mark, and a jump castle indicated by a △ mark. In the slip castle, the raw material only slips up and down along the side wall inside the drum mixer, and no rolling occurs, so pseudo-granulation does not proceed.

In a normal transfer case, the raw material is in a state of motion divided into a layer that rises up the side wall of the drum mixer and a layer that reversely flows down from the top.

In this case, pseudo-granulation occurs due to rolling during reverse flow, but in the same normal rolling region, the amount of transfer increases in the range where both the space factor and Froude number are high, so pseudo-granulation occurs as shown in Figure 2. Granulation is well promoted. In the bouncing state, the raw material is lifted high along the side wall due to centrifugal force, thrown out into the air, and falls all at once, and no rolling occurs.
In this case, since no rolling occurs, generation of pseudo particles is poor, and the generated pseudo particles are destroyed again by the impact of falling, so pseudo grain formation does not proceed. However, in the transition area between the normal rolling area and the jumping area, where more than 80% of the raw material rolls normally and less than 20% shows jumping, the amount of rolling is large and the amount of falling is small, so there is no impact. is also weak,
Pseudo-graining is at the same level as in the normal rolling castle described above when the space factor and Froude number are high, and pseudo-graining is well promoted.
That is, as shown in FIGS. 1 and 2, the upper limit of the space factor is 17%, and the space factor is 9 to 16.5%. If the rolling amount is less than this, the amount of rolling will decrease, and if it is more than this, the amount of jumping will increase and the possibility of re-fracture due to drop impact will increase, thereby worsening pseudo-graining. For Froude number, this is better, the upper limit is 18 × 10-3, 12.8 × 10-3 ~ 18 × 10
-3 is the optimal range. Froude number is 18×10-3
Anything above this is undesirable because it becomes a jumping castle and will be destroyed again, and anything below 12.8 x 10-3 is considered a normal rolling castle in terms of space factor, but the amount of rolling per unit time is small and a false This is not preferable because the mixing time for granulation increases. Because of the above relationship, it is necessary to satisfy both the space factor and Froude number conditions in order to promote pseudo-granulation, and good pseudo-granulation can be achieved even if only one of the two conditions is satisfied. cannot be obtained. Regarding the relationship between pseudo-granulation and residence time in the drum mixer, as shown in Figure 2, 4 minutes or more is required under any conditions for normal and partially sputtered rolling, but if it exceeds 6 minutes, After that, the pseudoparticles hardly grow.

Until now, the pseudo-granulation behavior of raw materials in a drum mixer was unknown, so operations were carried out with an occupancy rate of 9% or less and a Froude number of 12.8 x 10-3 or less.
For this reason, sufficient pseudo-granulation was not achieved and the ventilation of the arm-tie bed was insufficient, which was a factor that inhibited an increase in production rate. The present invention allows the functions of a drum mixer to be performed most efficiently, thereby increasing the production rate and improving the quality of the finished ore.

An example of the implementation of the present invention is shown in Table 1 in comparison with a conventional method using the same raw materials. Table 1: Hongo method and broadside female GI: Pseudo-granulation index GI = 1000 yen) ÷ 2 A: 0.5 to 0.25 rib weight% in raw materials A: 0.5 to 0.5 after pseudo-granulation 0.25 side weight% B: -0.25 side weight% in raw material B: -0.25 side weight% after pseudo granulation A) Normal rolling in Table 1 has a space factor of 12.5% , in the case of Froude number 12.8×103, B) has a space factor of 16.3%,
In the case of a Froude number of 12.8×10-3, both cases are within the scope of the method of the present invention.

C) is the conventional method when the space factor is 7.5% and the Froude number is 3.2×10-3. Further, D) is a comparative example in which the space factor is 12.5%, the Froude number is 7.5×10-3, and only the Froude number is outside the range of the present invention. A) which is the method of the present invention
Comparing B), C), which is a secondary method, and D), which is a comparative example, A) and B) are approximately 0 in terms of the average particle size of the raw material after pseudo granulation.
．． 5 skin size, and GI is 0.14 compared to conventional method C).
~0.18 higher. For this reason, there is a difference in air permeability after pseudo-granulation even though the raw materials are the same, and the production rate of the method of the present invention is approximately 4 t/D compared to the conventional method. That increase also resulted in an approximately 2% improvement in the strength of the finished product. In addition, as shown in Table 1, Comparative Example D), in which the space factor is within the range of the present invention but the Froude number is below the range specified by the present invention, is Compared to conventional method C) in which both the ratio and the Froude number are below the range specified by the present invention, the mixing time is increased and the productivity during granulation is inferior. From the above results, it was found that it is necessary to simultaneously adjust the space factor and Froude number within a specific range when taking into account granulation and coagulation properties.

The blending ratio of the raw materials used in this test is shown in Table 2, and the mixing, humidity control, and granulation were performed using diameters of 1. Blood, a drum mixer with a depth of 0.31 shoes was used. The Akatsukijima test uses a standard competitive test pot with a diameter of 30 ribs, a charging layer thickness of 350 mm, and an ignition of 90 mm.
The test was carried out under constant conditions of negative pressure 1600A). Table 2 Original column fin and clam note) () The outer frame is in parentheses.

[Brief explanation of drawings]

FIG. 1 shows the transfer status that occurs in a drum mixer for wet blended raw materials in terms of the relationship between the space factor and the Froude number. FIG. 2 shows the relationship between the GI (pseudo granulation index) and the residence time of the raw material in the drum mixer in each transfer state. Multi-figure multi-figure 2

Claims (1)

[Claims] 1. In at least one or more of the processes of mixing, humidity controlling, and granulating the sintered raw materials in a drum mixer, the space factor of the raw materials in the mixer is 9% or more, and the Froude number is 1.
A pseudo-graining method for a sintering raw material, characterized in that the particle size is 2.8×10^-^3 or more and 18×10^-^3 or less.