JPH05295454A - Strength estimating method of sintered ore for blast furnace - Google Patents

Abstract

PURPOSE:To estimate the strength of a sintered ore with extremely good accuracy by directly using the mixed raw material before sintering with a sintering machine. CONSTITUTION:Of the mixed raw material of the sintered ore for blast furnaces, raw material of the part having <=1mm grain size is taken out and packed into a prescribed container where the raw material is compression molded to form a sample; thereafter, the sample is fired in an electric furnace. The volume of the sample before and after the firing is measured and the strength of the sintered ore formed by using the mixed raw material mentioned above is estimated from the measured volumetric ratio. As a result, the fluctuation in the strength of the sintered ore at every change of the mixing ratio between each of the raw materials is prevented and the problem of an increase in the production cost of the sintered ore and the fuel ratio of the blast furnace is solved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of preliminarily estimating the strength of sinter, which is the main raw material of the blast furnace pig iron making process, at the stage of designing the blending raw material for sintering. It is intended to prevent fluctuations in the strength of the sinter.

[0002]

2. Description of the Related Art Generally, a raw material for a sinter for a blast furnace is 10 days to 2 days since foreign-made iron ore is imported by a large transport ship.
There is no choice but to change the mixing ratio of various iron ores once a day. Further, since iron ore has different components, particle sizes, etc. depending on each production area, there is a problem that the sinter ore production cost and the blast furnace fuel ratio increase due to variation in sinter ore strength each time the mixing ratio is changed.

Conventionally, in order to solve the above problems caused by changing the mixing ratio, the relationship between the components of the mixing raw material and the strength of the sinter or the relationship between the mixing ratio of various ore brands and the strength of the sinter according to the past sintering operation data. And the change in the sinter ore strength due to the change in the composition was estimated, and the compounding ratio of the powder coke as the fuel was controlled.

[0004]

The above-mentioned conventional method for estimating the strength of sinter uses the operation data of the actual sinter machine including the disturbance factors other than the change of the mixing ratio, and therefore the estimation accuracy is low, and the above-mentioned problem is encountered. Has not been completely resolved.

The present invention estimates the strength of sinter ore with extremely high accuracy and prevents the strength of the sinter from varying each time the blending ratio is changed, thereby increasing the sinter production cost and the blast furnace fuel ratio. It solves the problem.

[0006]

Means for Solving the Problem The gist of the present invention is to prepare a sample by taking out a portion having a particle size of 1 mm or less from a raw material for sinter for a blast furnace, filling it into a predetermined container, and compression-molding it. It is a method for estimating the strength of a sinter for blast furnace, which comprises firing in a post electric furnace, measuring the volume of the sample before and after firing, and estimating the strength of the sinter using the blended raw material from the volume ratio.

[0007]

In general, as a raw material for sinter, a mixture of about 5 to 15 kinds of iron ore and auxiliary raw materials such as limestone, silica stone, serpentine and quick lime is used, and these are collectively referred to as blended raw materials. The average particle size of the blended raw material is in the range of about 1.5 to 3 mm, and the proportion of 1 mm or less is 30 to 70%.

The sinter ore is prepared by mixing and blending the above-mentioned blended raw material with powdered coke which is a return ore, and charging the mixture into the bed layer of the sinter machine, igniting the uppermost surface, and then sucking air downward. The temperature in the bed is gradually raised, and melting is started from the fine powder portion of the raw material for production.

In the present invention, attention is paid to the fact that the melting starts from the fine powder portion of the compounded raw material and the sintering is performed as described above, and a portion where the particle diameter of the compounded raw material is 1 mm or less is filled in a predetermined container,
This is a method of preparing a sample by compression molding, firing it in an electric furnace, measuring the volume of the sample before and after firing, and estimating the strength of the sinter using the blended raw material from the volume ratio. The details will be described below.

With respect to the blended raw material planned as a raw material for sinter, various raw materials before blending are sampled and sieved to collect a portion having a particle diameter of 1 mm or less. A value obtained by multiplying a portion having a particle diameter of 1 mm or less of each of these various raw materials by a weight ratio having a particle diameter of 1 mm or less, which is obtained in advance, by a compounding ratio,
That is, a sample for estimating the strength of sinter ore is prepared by mixing the mixed raw materials according to the ratio of the raw materials in a portion having a particle diameter of 1 mm or less. It is also possible to sample the mixed raw material that has been mixed, and collect a portion of 1 mm or less to use as a strength estimation sample, but in this case, there is a large variation in sampling,
The method described above is desirable because the accuracy of intensity estimation may be reduced.

A fixed amount of 0.5 g or more of the above sample was weighed and filled in a cylindrical molding container having a diameter of 30 mm or less, and 4 kg / m.
Compression molding is performed by applying a certain amount of load of m ² or less. The height of the compression-molded sample is measured using a micrometer,
The volume is calculated by multiplying it by the diameter of the cylindrical molding container.
Next, the sample is fired in an electric furnace, and the maximum temperature is set to 1300 ° C. at 11 ° C. by approximating the heat pattern in actual sintering.
Temperature rising rate from 00 ℃ to maximum temperature is 200 ℃ / mi
n, cooling rate from maximum temperature to 1100 ° C is 70 ° C /
Bake as min. After firing, the sample volume is measured by the mercury method.

The reason why the sample weight is set to 0.5 g or more is that the representativeness of the sample is impaired if the sample weight is less than 0.5 g. Further, the reason why the cylindrical container is used as the molding container is that it is easier to obtain a uniform baking state of the sample at the stage of baking after molding as compared with a rectangular parallelepiped or a cube, and the sample diameter is 30 mm.
If it exceeds, the temperature on the surface of the sample during firing will be non-uniform and the accuracy of strength estimation will decrease. Furthermore, when the load during compression molding exceeds 4 kg / mm ² , the volume change before and after firing of the sample becomes small, and the difference in volume ratio before and after firing, which is an evaluation index in the present invention, becomes small between the samples having different formulations. It was found through experiments that the accuracy of strength estimation was reduced.

As an index for estimating the strength of the sinter, the shrinkage ratio (1-V ₂ / V ₁ ) of the sample due to firing is calculated from the sample volume V ₁ before firing and the sample volume V ₂ after firing. In the present invention, as shown in FIG. 1, the higher the shrinkage ratio, the higher the actual strength of the sintered ore. That is, the strength of the sinter has both a drop strength (JIS M8711-87) and a rotation strength (JIS M8712-87), which are correlated with the shrinkage rate.

[0014]

EXAMPLES First, the accuracy of the sinter ore strength estimated value by this method will be described.

FIG. 1 shows the relationship between the sinter strength when 10 kinds of compounded raw materials shown in Table 1 are actually sintered by a sinter and the shrinkage rate which is a strength estimation index in this method. The shrinkage rate is 2 kg / mm when 1 g of the sample is filled in a cylindrical container having a diameter of 8 mm.
After compression-molding with a load of ² , it was fired in an electric furnace and determined from the volume change before and after firing.

[0016]

[Table 1]

According to FIG. 1, it is clear that the estimation accuracy of this method is much higher than the estimation value of the conventional method, which was derived from the actual operation data of the relationship between the mixing ratio of various ore brands and the sinter strength. is there.

Next, the sintering operation results and blast furnace operation results using this method will be described.

As shown in FIG. 2, during the conventional operation period in which the sinter ore strength estimation according to the present invention was not used, the sinter ore strength varied each time the composition was changed. Although the strength is controlled by increasing / decreasing the amount of powdered coke blended, there is no choice but to take over action due to the post-management, and the fuel ratio of the blast furnace also fluctuates greatly. On the other hand, during the period when this method was applied, the strength of the sintered ore could be stabilized, and the increase / decrease in the amount of powder coke compounded decreased, resulting in a lower amount of powder coke compounded. In addition, the stable strength also reduced the blast furnace fuel ratio.

[0020]

INDUSTRIAL APPLICABILITY According to the present invention, the strength of sinter, which is a main raw material of the blast furnace pig iron making method, can be accurately estimated in advance at the blending design stage of the blending raw material for sintering. It is possible to prevent the fluctuation of the strength of the sinter before it can solve the problem of increasing the manufacturing cost of the sinter and the fuel ratio of the blast furnace.

[Brief description of drawings]

FIG. 1 is a diagram showing sinter ore strength estimation accuracy of the present method.

FIG. 2 is a diagram showing an operation transition during a conventional operation period and an application period of the present method.

Claims (1)

[Claims] 1. The particle size of the mixed raw material of sinter for blast furnace is 1
A portion of mm or less is taken out, filled in a predetermined container, compression molded to prepare a sample, and then fired in an electric furnace, the volume of the sample before and after firing is measured, and the blended raw material is used from the volume ratio. A method for estimating the strength of sinter ore for blast furnace to estimate the strength of sinter.