JPS627823A - Method for sintering hardly briquettable fine ore - Google Patents

Abstract

PURPOSE:To improve the sinterability of hardly briquettable fine ore by kneading the ore with converter sludge to stick the sludge to the surface of the re and to improve the pseudo-briquettability of the ore and by briquetting the ore. CONSTITUTION:About 40-70wt.% air-dried converter sludge having <=about 15% water content is added to hardly briquettable fine ore such as pellet feed and iron sand. They are kneaded with a ball mill, briquetted with a drum mixed and cured for about 12hr-7 days in a storage hopper. The cured briquetted ore is blended with about 3-9wt.% (expressed in terms of simple pellet feed) ordinary fine ore and the blend is sintered. Thus, the hardly briquettable fine ore is easily formed in to pseudo-briquettes.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for sintering difficult-to-granulate ore powder used as a raw material for iron manufacturing.

[Conventional technology]

When sintering to prepare raw materials for blast furnace operation,
In order to make the sintering reaction proceed uniformly, it is once made into pseudo-particles. It is important that these pseudo-particles are not easily affected by the conditions in which they are charged into the pellets such that the filling state deteriorates, and that they are maintained without collapsing during the sintering process.

Conventionally, 2~3+L was used as a pre-treatment for sintering ore.
Raw materials such as coke and limestone were mixed with water in a granulator to granulate ore powder having a particle size of about lff1.

[Problem that the invention seeks to solve]

The mechanism of this granulation is that, microscopically, the fine powder raw material adheres to the concave portions of the core particles to form pseudo particles. However, if a brand of raw material such as pellet feed or iron sand is used, the adhesion of fine ore may be poor and granulation may be difficult. If such difficult-to-granulate fine ore is directly used as a sintering raw material, ventilation will be inhibited during the sintering process, resulting in a decrease in productivity.

Therefore, as an improvement measure to improve the granulation and sinterability of such difficult-to-granulate ores, it has been proposed to use binders such as bentonite, but these binders increase impurities in the sintered ore. , deteriorate the quality,
Additionally, there was a problem of increased costs.

It has been found that ore powder, which is difficult to granulate, has a microscopically extremely smooth surface, which reduces the adhesion of fine ore powder and makes granulation difficult.

An object of the present invention is to provide a method for improving the adhesion of difficult-to-granulate ores, increasing pseudo-granulation properties, and improving sinterability.

[Means for solving problems]

This objective can be achieved by mixing and kneading converter sludge recovered from converter exhaust gas with difficult-to-granulate ore powder.

As is well known, converter sludge is an aggregate of micron-sized relatively high-purity iron oxide powder,
-41481 publication, JP-A-48-14513 publication,
Its use has been attempted as described in Japanese Unexamined Patent Publication No. 49-13002.

In the present invention, this converter sludge adheres to the surface of core grains of difficult-to-granulate ore materials such as pellet feed during granulation and kneading.
This product was developed based on the knowledge that it forms microscopic irregularities, and that fine ore particles penetrate and adhere to these irregular surfaces, promoting the formation of pseudo-particles, and that it has the same effect of improving air permeability as quicklime.

That is, converter sludge in the form of small lumps with a moisture content of 15% or less is added to fine powder of difficult-to-granulate ore, and the mixture is crushed and kneaded using a ball mill-type kneader to form a surface to which fine powder of difficult-to-granulate ore is attached. This yields particles with an uneven shape and improves the granulation properties of the difficult-to-granulate ore itself.

When sintering these particles, the granulation properties have been improved, but they are still fine and if used directly, they will cause ventilation obstruction, so ordinary powder ore prepared in a separate process without the addition of a binder is used, for example, in a drum mixer. It is best to use it by mixing it with particles granulated using.

Specifically, 40 to 70% by weight of air-dried converter dust is added to difficult-to-granulate ore powder, kneaded in a ball mill, granulated in a drum mixer, and then stored in a storage hopper for 12 hours or more. Train for 7 days. A normal binder is not added to the hard-to-granulate granulated ore after curing, but the granulated ore is mixed with 3 to 9 weight percent in terms of pellet feed alone and sintered.

Here, since the moisture content of converter sludge is approximately 30%, if it is used directly, it cannot be ground due to the limitations of the ball mill equipment, so if it is piled up in a yard and dried naturally, the moisture content will be reduced to 1.
It becomes 5% or less, which makes it possible to increase the content and facilitate surface adhesion and pseudo-granulation. For this reason, if the blending amount of converter sludge is less than 40% by weight, the pseudo particles cannot be strengthened due to insufficient self-oxidation exothermic hardening of the converter sludge itself;
If the amount is larger than this, the pseudo grains will collapse due to excessive self-oxidation heat generation of the converter sludge.

If the curing time in the storage hopper is less than 12 hours, the self-heating hardening of the sludge is insufficient, and pseudo particles are likely to be powdered during transportation or during charging into the sintering machine, impairing air permeability and quality of the sintered ore. On the other hand, if the curing is carried out for more than 7 days, the pseudo-particles will combine with each other due to self-heating curing to form large agglomerates and become unusable.

Of course, quicklime powder, which has conventionally been used as a binder to improve air permeability, can also be used for granulation, but converter sludge powder improves adhesion and air permeability, so The amount added may be smaller than that.

〔Example〕

Pellet feed fine powder with average particle size of 80-90μ 7.2
% by weight and 5.3% by weight of lumpy converter sludge with an average particle size of 2oIIIl in which iron oxide particles with an average particle size of 18m are aggregated, and crushed and kneaded in a ball mill to form particles with an average particle size of 8oμm. Obtained.

This was mixed with 87.5% by weight of powdered ore with good granulation properties that do not require the addition of a binder, with an average particle size of 25%.
IIl+1 pellets were prepared, and the pellet feed obtained by adding the converter sludge to the pellets was added to 1
2.5% by weight was added and sintered.

During the sintering process, these particles do not disintegrate in any way;
It is possible to obtain powder ore for sintering with an average particle size of 2.5μ,
Additionally, productivity improved by 4 to 5%.

〔Effect of the invention〕

The present invention allows converter sludge to be used in place of quicklime powder, which not only makes effective use of converter sludge, but also reduces the amount of quicklime used. It is possible to achieve the effect that various raw materials, which have been limited, can be used in large quantities.

Claims (1)

[Claims] 1. Difficult to granulate ore powder, which is characterized by adding converter sludge to difficult to granulate ore powder, kneading it, fixing fine particles on the surface of the difficult to granulate ore powder, and then granulating it. Sintering method.