JPH05255765A - Production of sintered ore - Google Patents

Abstract

PURPOSE:To ameliorate the degradation in air permeability in a sintering bed arising from an increase in coarse grained ore contg. many gangue components and to produce the sintered ore having improved cold strength with high yield by adequately adjusting the amts. of powdery CaO and MgO sources to be added at the time of pelletizing and the sintered ore. CONSTITUTION:The coarse grained ore contg. >=50wt.% particles of over 1mm grain sizes and having >=3wt.% SiO2 content and fine powder ore contg. >=80wt.% particles of <=1mum grain sizes are compounded at such ratios at which (the coarse grained ore)/(the fine powder ore) attain 10/10 to 30/10 by weight. Further, powdery quicklime and powdery dolomite are so compounded that the compounding ratio of the dolomite with 100 parts (the coarse grained ore + the fine ore) attains 2 to 23 pts. wt. The mixture is then pelletized. The resulted pellets are mixed with other main raw materials for sintering and auxiliary raw materials for sintering or are mixed therewith and are pelletized; thereafter, the pellets are charged into a sintering machine.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a sintered ore with high productivity by improving the air permeability during the production of the sintered ore using a coarse-grained ore containing a large amount of gangue components.

[0002]

2. Description of the Related Art As a raw material for iron ore for iron making, the amount of fine ore or coarse ore containing many gangue components tends to increase. Fine-grained ores and coarse-grained ores containing a large amount of gangue components are less expensive than conventional high-grade coarse-grained ores, and when a large amount of these raw materials are compounded, the production cost of the sintered ore is reduced.

However, a coarse-grained ore containing a large amount of gangue components produces a large amount of melt during the sintering process, which causes air permeability during sintering together with the fine ore and reduces the yield of the sintered ore. Therefore, in order to improve the deterioration of air permeability, after finely granulated ore and partially coarse-grained ore are granulated in advance to form pseudo particles, they are mixed or granulated with other main raw materials and auxiliary raw materials to a sintering machine. Various proposals have been made so far regarding charging. For example, in Japanese Examined Patent Publication No. 60-17811, use is made of sintering mini pellets whose particle size classification is specified.
In Japanese Patent No. 10, the sintering raw material is pretreated by specifying the mixing ratio of coarse-grained ore.

[0004] In order to improve the deterioration of air permeability due to melting of coarse ore having many gangue components, solid fuel and granulated coarse ore are charged between other sintering main / auxiliary materials and bedding. Japanese Unexamined Patent Publication (Kokai) No. 3-130326 proposes sintering. In this method, a coarse ore such as a high goethite ore containing a large amount of gangue components is sintered into a sinter under the condition that combustion is controlled by segregation insertion. In addition, Japanese Patent Laid-Open No. 4-1
In Japanese Patent No. 3818, coarse ores that have been granulated with MgO—SiO ₂ -based raw material in advance are mixed and granulated with other sintering main and auxiliary raw materials.

[0005]

In the method of Japanese Patent Laid-Open No. 3-130326, which uses coarse-grained ores such as high goethite ores, there is a restriction on the compounding ratio of the coarse-grained ores to all the sintering raw materials, and the coarse-grained ores are included. It is not possible to produce sinter using a large amount of. On the other hand, in the method described in JP-A-4-13818, overmelting of the coarse-grained ore is suppressed by preliminarily granulating the MgO—SiO ₂ -based raw material with the coarse-grained ore. However, the use of MgO-SiO ₂ -based raw material is
Increasing the O ₂ content causes high slag.

When coarse-grained ore containing a large amount of gangue components is used as a raw material for iron making, the SiO content of the sintered ore, which causes high slag
₂ It is necessary to improve the deterioration of air permeability of coarse-grained ores with many gangue components without increasing the content. As a result, a large amount of low-grade coarse-grained ore can be used, and the sinter production cost can be reduced.

The present invention has been devised in order to meet such a demand, and by appropriately adjusting the amounts of the powdered CaO and MgO sources added at the time of sinter and granulation, the gangue component can be obtained. It is an object of the present invention to improve the decrease in air permeability in a sintered bed due to the increase in the amount of coarse-grained ore, and to produce a sintered ore with improved cold strength at a high yield.

[0008]

In order to achieve the object, the method for producing a sinter according to the present invention contains 50 wt% or more of particles having a particle size of more than 1 mm and SiO ₂ content of 3 wt% or more. Coarse-grained ore and fine-grained ore containing 80% by weight or more of particles having a particle diameter of 1 mm or less are (coarse-grained ore) / (fine-grained ore)
Is mixed at a ratio of 10/10 to 30/10 by weight, and further, powdered quick lime and powdered dolomite are mixed in a proportion of 2 to 23 parts by weight with respect to 100 parts of (coarse ore + fine ore). It is characterized in that it is mixed and granulated as described below, and the obtained granulated product is mixed or mixed with other main sintering raw materials and auxiliary sintering raw materials, and then charged into a sintering machine.

[0009]

[Operation] In order to suppress overmelting of coarse-grained ore containing a large amount of gangue components having a SiO ₂ content of 3% by weight or more, it is effective to add a MgO source to the sintering raw material. MgO added
Sources include serpentinite and dolomite. In this regard, in JP-A-4-13818, MgO-SiO
Serpentinite added as ₂ source, and granulating the sintered material.
However, in order to improve the quality of the sintered ore, the required Mg
It is necessary that the gangue component other than O is small.

As shown in Table 1 of the average composition of serpentinite, the SiO ₂ component is abundant at about 40% by weight. On the other hand, dolomite has a SiO ₂ component of 0.
It is as low as 2% by weight. Therefore, dolomite should be used to reduce the slag of the sinter.

[0011]

[Table 1]

The inventors of the present invention added the dolomite as a MgO source to a low-grade ore to produce a sinter, while maintaining a low SiO ₂ composition of the sinter and producing a melt of coarse-grained ore. In order to suppress the above, improve the air permeability, and improve the yield and the cold strength of the sintered ore, coarse ore, fine ore and powdery flux [quick lime (CaO), dolomite (C
and a aCO ₃ · MgCO _3] to the appropriate granulation conditions and granules obtained by granulating (hereinafter, preliminary called granules) to be the strength of the sintered high enough I found out that there is.

Therefore, granulation experiments were carried out on coarse-grained ores and fine-grained ores, and appropriate granulation conditions were examined. As a result, when the (rough-grained ore) / (fine-grained ore) weight ratio was in the range of 0 to 10/10, the amount of the ore serving as the core was small, and thus the granulation did not proceed. Further, even in the range where the weight ratio of (coarse ore) / (fine ore) exceeds 30/10, the amount of powder adhering to the nuclear ore was insufficient, and no progress of granulation was observed. And
The proper mixing ratio of coarse ore and fine ore is such that the weight ratio of (coarse ore) / (fine ore) is 10/10 to 30/10.
It was found to be in the range of.

During granulation, the grain size distribution may vary depending on the brand of coarse-grained ore, and the granulation property may deteriorate. In such a case, by adding quick lime to improve the granulation property, (coarse ore) / (fine ore) = 10/10 to 30 /
Appropriate granules can be obtained in the range of 10. However, it is preferable to add quick lime at a ratio of 7 parts or less with respect to 100 parts of the entire granulation raw material. When the addition ratio of quick lime exceeds 7 parts, the adhered powder layer causes over-melting during sintering,
A phenomenon that deteriorates air permeability is likely to occur.

Next, a strength test is conducted after firing a preliminary granulated product consisting of coarse ore, fine ore and dolomite.
The amount of dolomite added to obtain appropriate strength was examined.
The results are shown in FIG. 1 as the relationship between the amount of dolomite added to the pre-granulated product and the strength of the pre-granulated product after firing. As is clear from FIG. 1, the amount of dolomite added to obtain desired strength is (coarse ore) / (fine ore) = 10/10 to 3
In the range of 0/10, (coarse ore + fine ore) 10
It was 2 to 23 parts by weight for 0 part by weight.

In this way, when the proportion of the coarse ore and the fine ore and the addition amount of dolomite to the fine ore are properly maintained, even if a large amount of low-grade coarse or fine ore is used, SiO ₂ A sintered ore having excellent strength can be obtained without increasing the content.

[0017]

Example A limonite-based ore from Australia (hereinafter simply referred to as limonite) having a SiO ₂ component of 3% by weight or more was used as a low-grade coarse ore, and a fine-grained ore from South America was used as a fine ore. Limonite and fine ore were mixed with powdered quick lime and dolomite in the mixing ratios shown in Table 2 to form a preliminary granulated product. The particle size composition and chemical components of the used limonite and fine ore are shown in Tables 3 and 4, respectively. In the pre-granulated product, limonite became nuclei of pseudo particles, on which fine ore and other raw materials were attached.

[0018]

[Table 2]

[0019]

[Table 3]

[0020]

[Table 4]

The example is an example in which 12 parts by weight of dolomite and 2 parts of quick lime were mixed with 100 parts by weight of limonite and fine ore according to the present invention. Comparative Example 1 is a case in which dolomite is not mixed, Comparative Example 2 is a case in which dolomite in an appropriate range or more is mixed, and Comparative Example 3 is a case in which serpentine is used as a MgO source. In any case, the amount of coke added was adjusted so that the maximum temperature reached during sintering was about 1250 ° C. Also, fine ore from Australia and fine ore from South America were used as main sintering materials other than the preliminary granulation material, and serpentine, silica stone powder and limestone powder were used as auxiliary materials.

In the preliminary granulation step, limonite, finely powdered ore, quick lime, dolomite, etc. were charged into a drum type granulator and granulated for a predetermined time with a preliminary granulation water content of 9.0% by weight. Then, the obtained pre-granulated product was charged into a drum type granulator together with other sintering raw materials, and was mixed and granulated at a granulation water content of 6.5% by weight for a predetermined time.

The granulated sintering raw material is fired at a maximum temperature of 1250 ° C. and a suction negative pressure of 11 in accordance with the Iron and Steel Institute's pig iron section method.
It was subjected to a sintering pot test under a constant condition of a water column of 00 mm. The sintered ore was evaluated by the sintering time, the yield (the rate at which a sintered ore having a particle size of 5 mm or more is obtained), the JIS reduction rate and the reduction powdering index. The results of the sintering pot test are shown in Table 5.

[0024]

[Table 5]

As is clear from Table 5, it is understood that the examples of the compounding ratio to which the present invention is applied have shorter sintering time and improved air permeability as compared with Comparative Examples 1 and 2. Also,
The yield was good, and the result was that the productivity was improved by shortening the sintering time. On the other hand, in Comparative Example 3, when compared with the sintered ore of the Example, there was no difference in the production rate, etc., but the SiO ₂ content of the sintered ore was high, and a furnace condition with high slag was exhibited. .. The reducing properties did not differ greatly under any of the conditions.

[0026]

As described above, in the present invention, when the sintering raw material is pre-granulated to produce a sintered ore, the addition amount of dolomite and quick lime added during the pre-granulation is adjusted. Thus, the melt generation of coarse-grained ore containing a large amount of gangue component that melts and hinders air permeability is suppressed, air permeability of the sintering bed is ensured, and smooth sintering reaction is promoted.
As a result, it is possible to produce a high-strength sintered ore with a high yield by using a large amount of inexpensive low-grade coarse-grained ore without inviting an increase in the SiO ₂ content that causes high slag. Becomes Further, the obtained sintered ore has a large cold strength, and it is suppressed that it is pulverized during handling.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between the amount of dolomite added and the strength of a preliminary granulated product.

Claims (1)

[Claims] 1. 50% by weight of particles having a particle size of more than 1 mm
The coarse ore containing 3% by weight or more of SiO ₂ and the fine ore containing 80% by weight or more of particles having a particle diameter of 1 mm or less are contained in the following manner: (Coarse ore) / (Fine ore) 10
/ 10 to 30/10, and powdered quicklime and powdered dolomite were added (coarse ore + fine ore) 10
After blending and granulating so that the blending ratio of dolomite to 0 part is 2 to 23 parts, the obtained granulated product is mixed or granulated with other sintering main raw materials and sintering auxiliary raw materials, A method for producing a sintered ore, which comprises charging into a sintering machine.