JPH07252541A - Method for adjusting grain size of lime stone for sintering iron ore - Google Patents

Abstract

PURPOSE:To reduce sintered ore excellent in property of reduction degradation impellent without lowering the sintering yield by adjusting the grain size of lime stone in the raw material in a specific range, at the time of producing the sintered iron ore in a sintering machine provided with a segregation intensifying type charging device. CONSTITUTION:At the time of producing the sintered ore for blast furnace by sintering powdery raw material with composition composed of the powdery ore as the main component and coke, lime stone and return fines, the grain size segregation in the layer thickness direction of the sintering raw material is intensified with the segregation intensifying type charging device, and also, the ratio of 3-5mm grain size part in the used lime stone is adjusted to be in the range of 10-30% to the whole charging quantity of the lime stone. While avoiding the lowering of the sintering yield caused by insufficient slagging because of too large grain size of the lime stone, i.e., insufficient reaction with the iron ore, the sintered ore excellent in the property of the reduction degradation impellent is produced in the high productivity.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for adjusting the particle size of limestone, which is one of the raw materials for producing iron ore self-fluxing sinter.

[0002]

2. Description of the Related Art A self-fluxing sinter used as a raw material for a blast furnace is generally manufactured by the following method. First, the ores unloaded from the ship are piled up by brand and lot in the yard, and then piled and mixed at a predetermined ratio to form a blended ore. The blended ore and raw materials such as limestone, powder coke and return ore are put in a sintering compounding tank and continuously cut out at a predetermined ratio. This blended raw material is granulated while adding water with a drum mixer, and then sent to a sintering machine. In the sintering machine, charge the blended raw materials.
It is fired by ignition and downward suction ventilation, and baked into a sinter cake. This is crushed and sized to a predetermined particle size to obtain a sintered ore.

Regarding the particle size of limestone used in the production of such a sintered ore, it is generally 3 mm or less (however, 3% of a few% is used) in order to sufficiently slag within a reaction time of several minutes. The above is allowed in the purchasing standard) has been used. Further, in order to improve the reduction pulverization property, which is one of the qualities of sinter, the particle size adjusting method as shown in Table 1 has been conventionally used.

[0004]

[Table 1]

On the other hand, a segregation-strengthened charging device has been introduced in recent years for the purpose of improving the sintering production cost. By adopting a chute having a sieving function in place of the conventional sloping chute, the grain size segregation of fine grains in the upper layer of the raw material grain size and coarse grains in the lower layer is positively carried out, and Japanese Patent Publication No. 59-30766. There is a slit bar type disclosed in Japanese Patent Publication No. 60-253435 and an ISF type disclosed in Japanese Patent Publication No. 60-253435.

[0006]

Although the segregation strengthening type charging device has been introduced in recent years, the particle size segregation in the layer thickness direction of the sintering raw material has shifted to a strong direction, but the limestone particle size has not been reviewed. The sintering operation is continued with the conventional 3 mm or less. Therefore, in the conventional method, as described later, the productivity and the reduction pulverization property were lowered.

Further, the following problems also occur with each of the particle size adjusting methods. In other words, is that there is no effective usage of limestone of 0.5 mm or less.
It is not practical because there is no efficient means for adjusting the ratio of mm or less. As for and, in a sintering machine having a segregation strengthening type charging device, 3 to 5 mm is 10
%, The reduction powderability is improved, but the productivity improvement effect cannot be expected, or there is a productivity improvement effect associated with coarsening, but it is too coarse and there is a problem with slagability, and the sintering yield There was a concern that

The present invention provides a proper method for adjusting the limestone particle size under the condition of strong particle size segregation, thereby avoiding a decrease in sintering yield due to insufficient slag formation due to too large particle size, that is, insufficient reaction with iron ore. At the same time, the object is to produce a sintered ore having good reduction powderability with high productivity.

[0009]

DISCLOSURE OF THE INVENTION The present invention is directed to the particle size of limestone for sintering iron ore used in a sintering machine equipped with a raw material charging device having a chute having a sieve function for strengthening particle size segregation in the thickness direction. In the adjusting method, the ratio of the particle size classification of 3 to 5 mm is set to the range of 10 to 30% with respect to the total weight of the limestone.

[0010]

In order to solve the above-mentioned problems, the present invention provides a grain size of 3 mm or more, which has been conventionally limited, to 3 to 3 under strong grain size segregation conditions.
By using an appropriate amount only in 5 mm, productivity is improved and reduction powdering property is improved.

First, the grain size segregation in the layer thickness direction of the sintered packed bed and the actual state of limestone segregation will be described. The raw material cut out from the drum feeder of the sintering machine is changed in direction by the chute and charged into the pallet.
At this time, when the particles roll and fall on the formed slope, the fine particles stop at the upper part, but the coarse particles roll to reach the lower layer, so that the particle size segregation occurs in the layer thickness direction due to the classification effect due to the particle size difference. This classification action depends on the type of chute, and the segregation-strengthened type chute such as a slit bar or ISF has a larger size than the conventional simple sloping chute. The limestone in the sintering raw material is also affected by this grain size segregation action, and the coarse grain portion of the limestone is unevenly distributed in the lower layer and the fine grain portion is unevenly distributed in the upper layer with the average grain size of the entire raw material of 2 mm as a boundary.

(1) (Productivity improvement effect) By coarsening limestone, the overall grain size is improved (coarsening), the air permeability of the sintering raw material packed layer is improved, and the sintering productivity is improved. .

(2) (Reducing pulverizability (RDI) improving effect) Coarse-graining of limestone promotes uneven distribution of micro lime concentration of about one ore particle, which is high CaO inside the sinter.
The formation of the tissue and the low CaO structure is promoted, and both of them are superior to the reduction powdering property, so that the reduction powdering property as a whole is improved.

(3) (Effect of Preventing Yield Reduction Due to Deterioration of Slagging Property) The problem of slagging property, which is a constraint for coarsening of limestone, can be avoided as follows. That is, when the coarse particle size segregation is strengthened, the coarse particles of 3 to 5 mm can be made to generally exist in the lower layer of the raw material packed layer as described above. Since the lower layer has a heat margin compared to the upper middle layer, the grain size of 3 to 5 mm is 10 to 10.
In the range of 30%, it can be sufficiently slagged. However, there is a risk that excessive grain coarsening may lower the sintering yield even in the lower layer due to poor slag formation.

In summary, when the segregation strengthening charging device is used, if 3 to 5 mm is set to 10% or less, the productivity is lowered due to the fine graining of the raw material and the RDI is deteriorated, and 3 to 5 mm is 30% or more. If this is the case, the yield will decrease.
.About.5 mm was set to 10 to 30%.

The grain size of limestone is generally adjusted by adjusting the opening of the final sieve in the limestone crushing process step to about 3 mm to 5 mm. In this case, +3 mm of about 3% is practically included, but it does not significantly impair the effects of the present invention. The other particle size classification may follow the natural particle size distribution in this case, and 1 to 3 mm is 3
0%, 1 mm or less is practically about 50%.

The present invention is intended for the production of general self-fluxing sinter, and the components of the sintering raw materials other than limestone are iron ore 85%, limestone 13%, and SiO ₂ adjusting raw material such as serpentine. About 2% of new raw materials, 20% of return ore and 3%
A mixed raw material containing powder coke is assumed.

[0018]

EXAMPLE Two different types of segregation strengthening charging devices currently in practical use (slit bar described in Japanese Patent Publication No. 59-30776 and ISF described in Japanese Patent Publication No. 60-253435) are provided at two locations. Table 2 shows the results of the limestone particle size change test conducted in the sintering machine.

[0019]

[Table 2]

If the grain size is excessively coarsened, the yield is lowered and the productivity improving effect cannot be confirmed (Test No. 2). However, if the limestone coarsening is within the scope of the present invention, a slit bar (Test No. 1) is used. ) -In the case of any of the charging devices of ISF (test number 3), the productivity was improved and the reducing powdering property was improved.

[0021]

EFFECTS OF THE INVENTION According to the present invention, in a sintering machine having a segregation charging device, it is possible to produce a sintered ore having a good reduction powdering property with high productivity without lowering the sintering yield.

Claims (1)

[Claims] 1. A method of adjusting the particle size of limestone for iron ore sintering, which is used in a sintering machine equipped with a raw material charging device having a chute having a sieve function for strengthening particle size segregation in the thickness direction.
The ratio of particle size classification of 3 to 5 mm is 10 with respect to the total weight of limestone.
The method for adjusting the particle size of limestone for iron ore sintering is characterized in that the range is -30%.