JPH09143578A - Briquetting method for reduced iron pellet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form briquettes chargeable into an iron making furnace, such as blast furnace and to effectively utilize iron oxide dust without imparting cost effectiveness by pressure forming the reduction roasted pellets of the iron oxide dust at and under a specified temp. and pressure. SOLUTION: The reduced iron pellets which are the residue after recovery of valuable metals and are formed by subjecting the dust contg. the iron oxide, i.e., iron and steel dust together with a carbonaceous reducing agent are heated to >=700 deg.C in an N2 atmosphere and are charged into metal molds. The pellets are then press molded under a pressure of 200 to 300kg/cm<2> . The briquettes sized 40mm diameter × 20mm produced by the method exhibit crushing strength of 35 to 49kg at 700 deg.C and about 50 to 74kg at 900'C. The briquettes are thus usable as an iron source of a high grade which has a decreased possibility of breakage during handling or after charging into an iron making furnace.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming reduced iron pellets as an iron source into a form that can be charged into an ironmaking furnace such as a blast furnace.

[0002]

Dust containing iron oxides such as Zn,
Reduction and roasting of so-called steel dust containing Pb, Z
Most of the reduced iron pellets remaining after recovering valuable metals such as n and Pb are used in landfills or used and treated as roadbed materials, cement materials and the like. However, since this reduced iron pellet contains 50% or more of Fe, and most of it is once reduced to metallic iron, it is desired to be recycled as an ironmaking raw material.

By the way, in order to use it as a raw material for iron making, the quality of iron as metallic iron is high, it is hard to be reoxidized during handling, and it has a certain size in terms of handling and ensuring ventilation in the ironmaking furnace. Must be pellets and the pellets must be hard. However, the reduced iron pellets described above are pulverized in a rotary kiln, and there are particles with a reduced particle size, and as a result, dust is easily generated,
When thrown into an iron-making furnace, it is likely to scatter or cause ventilation isolation. Therefore, it is said that the reduced iron pellets described above are not suitable as a raw material for iron making as they are.

Therefore, it is necessary to improve the properties of the reduced iron pellets so as to satisfy these conditions. As a method for achieving this object, briquetting by using a pressure molding method can be considered, but molding conditions for manufacturing the above reduced iron pellets have not been known.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for converting reduced iron pellets into briquettes that can be processed by iron and steel makers as iron raw materials.

[0006]

The method of the present invention for solving the above-mentioned problems is a reduced iron obtained by granulating dust containing Fe into pellets and reducing and roasting with a carbonaceous reducing agent. In the method of briquetting pellets,
Temperature 700 ° C or higher, pressure 200 kg / cm ^{2 to} 300 k
It is a group of reduced iron pellets characterized by being pressure-molded at g / cm ² .

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The inventors conducted research on the temperature and pressure at which pellets briquette, and found the temperature and pressurization pressure necessary for briquetting.

The evaluation of briquette strength in the present invention is to show the load value when the briquette on the pedestal is broken by applying a load with a pressure rod.

As shown in Table 1 below, the relationship between the temperature of the pellets and the crushing strength when briquetting is such that the strength increases as the temperature increases, but at 600 ° C, molding occurs at a temperature of 700 ° C or higher. Since the briquette strength is extremely reduced as compared with the above case, it is desirable to perform molding at a temperature of 700 ° C or higher.

Regarding the pressurizing pressure as well, the strength increases with an increase in the pressure, but when it exceeds 400 kg / cm ² , the briquette strength decreases. Further, as a result of observing the obtained molded body, it was confirmed that when the pressure applied exceeds 300 Kg / cm ² , the primary particles are broken, chipping occurs, and powder is generated. From this result, the present inventors consider that the pressurization pressure of 200 to 300 kg / cm ² , which is a low range where primary particles are not crushed or is low, is appropriate. Certainly, if a higher pressurizing pressure than that in Table 1 is applied, briquette strength increases, but selection of such a high pressurizing pressure impairs economic efficiency in consideration of equipment and the like. .

The phenomenon that the briquette strength decreases at 400 kg / cm ² is that the bond between original particles (hereinafter referred to as primary particles) becomes stronger and the strength is improved as the pressure is increased. It is considered that when the pressure is further increased, the strength limit of the primary particles is exceeded, the particles are broken, and the particles are pulverized, so that the strength is reduced. However, 500kg / c
At m ² or more, the briquette strength becomes high again, which may be due to the fact that broken fine particles are solidified again by pressing.

If the briquetting is carried out by pressurizing as in the present invention, the surface area of the pellet which comes into contact with the air will be reduced as a result, so that the effect of suppressing the reoxidation of metallic iron can be expected.

[0013]

Next, the present invention will be further described with reference to examples.

Example 1 Using an electric furnace, T-Fe 5
5.0, CaO 17.0, SiO ₂ 8.5, C
2.0 Reduced iron pellets each having a composition of each weight% were heated at 700, 800, and 900 ° C. for 5 hours under N ₂ atmosphere, charged into a mold by 70 g, and then pressed by a press machine at 100-6.
Immediately molded at a pressure of 00 kg / cm ² and a diameter of 40 m
A briquette of mΦ × 20 mm thick was obtained.

The strength of the obtained briquettes was measured, and the results are shown in Table 1.

[0016] (Comparative Example 1) Using an electric furnace, the reduced iron pellets of Example 1 were charged into a mold in the same amount as in Example 1 without heating (room temperature), and 100 to 600 kg / cm ² using a pressing machine. The briquette was not obtained though it was molded under the pressure.

(Comparative Example 2) Using an electric furnace, the reduced iron pellets of Example 1 were heated to 600 ° C under N ₂ atmosphere and charged in the same amount as in Example 1 into a mold, and a press machine was used. Immediately under pressure of 200 and 300 kg / cm ²
A briquette of mmΦ × 20 mm in thickness was obtained.

The strength of the briquette thus obtained was measured. The results are shown in Table 1 and the measurement results of the briquette strength are shown.

[0019]

Industrial Applicability According to the method of the present invention, it is possible to obtain a briquette having no problem in handling and air permeability when recycling reduced iron pellets as a raw material for iron making.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Nobuyuki Kii 17-5 Isoura-cho, Niihama-shi, Ehime Prefecture Niihama Research Center, Metal Business Division

Claims (1)

[Claims] 1. A method for briquetting reduced iron pellets obtained by granulating dust containing iron oxide into pellets and reducing and roasting them together with a carbonaceous reducing agent, at a temperature of 700 ° C. or higher and a pressure of 200 kg. / Cm ^{2 to} 300 kg /
A method for producing reduced iron pellets, which comprises press-forming at cm ² .