JPS6052532A - Pretreatment of starting material for sintering - Google Patents

Abstract

PURPOSE:To prepare a starting material for sintering giving sintered ore which is inhibited from causing a powering phenomenon in a low temp. reduction zone by pregranulating limestone powder, mixing it with fine iron ore, coke breeze, return ore, etc., and pelletizing the mixture. CONSTITUTION:A mixer 3 for pregranulation is placed at the inlet side of a primary mixer 1 to pregranulate limestone powder or the powder and quick lime powder. The pregranulated limestone powder is fed to the mixer 1 together with other starting materials for sintering such as fine iron ore, coke breeze and return ore, and after adding a prescribed amount of water, they are mixed. The mixture is fed to a secondary mixer 2, pelletized, and charged into a sintering apparatus as pseudo pellets. The resistance of sintered ore to powdering under reduction is improved economically and efficiently.

Description

DETAILED DESCRIPTION OF THE INVENTION 1- The present invention relates to a method for pre-processing sintered raw materials in order to suppress the pulverization phenomenon of sintered ore in a low-temperature reduction region of 400 to 600°C.

One of the properties required of sintered ore as a raw material for blast furnace charging is resistance to reduction and pulverization, which suppresses the pulverization phenomenon of sintered ore in the low-temperature reduction range of 400 to 600°C. That is, when sintered ore with deteriorated resistance to reduction and pulverization is charged into a blast furnace, air permeability decreases and furnace conditions become unstable during blast furnace operation.

Therefore, in order to prevent such deterioration of the blast furnace situation,
Conventionally, the reduction index (RDI) of sintered ore has been managed by the following method.

■ Increase in the amount of coke powder mixed in the sintering raw material.

■ Components of iron ore powder For example, A40s/5i0 of the fine powder part
Strengthening binary management.

■ Coarse graining of limestone powder by sieving.

However, the above method (2) causes an increase in fuel consumption, the above method (2) requires crushing of iron ore, and the blending of iron ore powder is restricted. There were problems such as the need to dispose of the finely divided limestone that had been separated and removed.

The present inventors solved the above-mentioned problems and developed a method for economically and efficiently improving the reduction resistance of sintered ore without affecting the properties and composition of raw materials. I did as much research as possible.

Raw materials such as iron ore powder, coke powder, limestone powder, and return ore, which are charged into a normal Dwight Lloyd sintering machine in the production of sintered ore, are placed in advance in the primary mixer 1 as shown in Figure 1. supply and mix these with the addition of a predetermined amount of water,
Next, the mixture is supplied to the secondary mixer 2 and granulated to form pseudo particles, and then charged into a sintering machine.

For this reason, limestone is refined into fine particles, but refinement of limestone is equivalent to an increase in its reaction interface area. , the contact area between the limestone particles and the iron ore powder is relatively large. As a result, a large amount of calcium ferrite is produced during the sintering process, and secondary hematite is produced by contact assimilation of this calcium ferrite and 5j02. This secondary hematite causes reduction and powdering, and as the secondary hematite increases, the resistance to reduction and powdering deteriorates.

From the above, the present inventors have found that reducing the reduction powdering resistance can be improved by reducing the contact area between calcium ferrite and iron ore.

This invention was made based on the above knowledge, and involves mixing sintering raw materials such as iron ore powder, limestone powder, coke powder, and return ore with a mixer while adding a predetermined amount of water, and then granulating the mixture. In the method for pre-processing sintering raw materials, after pre-granulating the limestone powder, the pre-granulated limestone powder is mixed with other sintering raw materials such as the iron ore powder, coke powder and return ore, and then granulated. It is characterized by its grain size.

Next, the present invention will be explained with reference to the drawings.

3- FIG. 2 is an explanatory diagram showing the pre-processing step of the present invention.

As shown in FIG. 2, in the method of this invention, a mixer 3 for preliminary granulation of limestone powder is provided on the inlet side of the primary mixer 1, and in the mixer 3 for preliminary granulation, limestone powder or limestone powder and quicklime powder are mixed. and are pre-granulated for a predetermined period of time. Next, the above pre-granulated limestone powder is supplied to the primary mixer 1 together with iron ore powder, coke powder and return ore, and these are mixed with the addition of a predetermined amount of water, and then the mixture is is supplied to the secondary mixer 2 and granulated to form pseudo particles, and then charged to the sintering machine.

FIG. 3 is a graph showing the relationship between the preliminary granulation time of limestone and the reduction pulverization index (RDI of sintered ore of 31 Tan or less). It can be seen from FIG. 3 that the reduction powdering index is significantly improved as the pregranulation time increases.

FIG. 4 is a graph showing the relationship between the preliminary granulation time of limestone and the harmonic average particle diameter of limestone powder. In FIG. 4, black circles indicate the case where only limestone powder is used, and white circles indicate the case where limestone powder is mixed with quicklime in an amount of 2.4 - of the blending ratio of the limestone powder. It can be seen from FIG. 4 that the harmonic mean particle size becomes smaller as the pregranulation time increases.

FIG. 5 is a graph showing the relationship between the preliminary granulation time of limestone, the production rate, and the sintering rate. It can be seen from FIG. 5 that the sintering rate and the sintered ore production rate increase as the pregranulation time increases.

Figure 6 shows the preliminary granulation time, reduction rate (RI), and shutter strength of limestone (sintered ore dropped from a height of 2 m onto an iron plate), and the ratio on the sieve when sifted through an Om sieve. It is a graph showing the relationship between It can be seen from FIG. 6 that as the pre-granulation time increases, the reduction rate (RI) increases, and the shutter strength is almost the same as in the case without pre-granulation.

FIG. 7 is a graph showing the relationship between the harmonic mean particle diameter of limestone and the reduction pulverization index obtained by preliminary granulation. In Figure 7, the black circles indicate the harmonic mean particle diameter of limestone after pre-granulation, which is obtained by pre-granulating limestone with a washed particle diameter of 35 mm, and the open circles indicate the harmonic mean particle diameter of limestone without pre-granulation as described above. It is the diameter.

It can be seen from FIG. 7 that the reduction powdering index is determined by the particle size.

As described above, according to the method of the present invention, it is possible to economically and efficiently improve the reduction powdering resistance of sintered ore without affecting the properties, composition, etc. of raw materials. ,
Many excellent effects are brought about in industry, such as making it possible to effectively utilize finely divided limestone with a diameter of between 0 and 25 mm, whose use was previously restricted.

[Brief explanation of drawings]

Figure 1 is an explanatory diagram showing the conventional pre-treatment process of sintering raw materials;
Figure 2 is an explanatory diagram showing the pre-treatment process of the sintered raw material of this invention, Figure 3 is a graph showing the relationship between preliminary granulation time and reduction powdering index, and Figure 4 is a graph showing the relationship between preliminary granulation time and particle size. 5 is a graph showing the relationship between preliminary granulation time, production rate, and sintering rate. FIG. 6 is a graph showing the relationship between preliminary granulation time, reduction rate, and shutter strength. FIG. 7 is a graph showing the relationship between particle size and reduction powdering index. In the drawings, 1... primary mixer, 2... secondary mixer, 3...
...Mixer for preliminary granulation. Applicant Nippon Kokan Co., Ltd. Agent Natsuo Shioya (and 2 others) c%J(""r-) ICJ'd (%)I! J4 Niichi&”-person< (%)F Shin'M7i
[%] ("m9-) IO"d Akanemachi

Claims (2)

[Claims] (1) A method for pre-processing sintered raw materials, in which sintered raw materials such as iron ore powder, limestone powder, coke powder, and return ore are mixed with a mixer while adding a predetermined amount of water, and then granulated. Pre-treatment of sintering raw materials, characterized in that after pre-granulation, the pre-granulated limestone powder is mixed with other sinter raw materials such as the iron ore powder, coke powder and return ore and granulated. Method. (2) Claim No. 1, characterized in that a predetermined amount of quicklime is mixed into the limestone powder to be pre-granulated.
) The method for pre-treatment of sintering raw materials as described in section 2.