JPH10324929A - Production of sintered ore - Google Patents

Abstract

PROBLEM TO BE SOLVED: To control the sintering to desired reducing powdering or reducibility by quickly estimating the reducing powdering and the reducibility of product sintered ore on the way of sintering in a producing process of the sintered ore. SOLUTION: The cross sectional picture of sintering filled layer 8 is picked up with CT scanners 4, 5, 7 and the range of coke burning in the raw material is discriminated to obtain the porosity and the average pore diameter in this range. Either or both of grain sizes of powdery coke and lime stone blended into the sintering raw material are adjusted so that the porosity and the average pore diameter become the values in the prescribed ranges.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a method for producing a sinter used as a raw material for a blast furnace, and more particularly to a method for producing a sinter which controls the reduction pulverizability and reducibility thereof.

[0002]

2. Description of the Related Art At present, a general sinter production process is as follows. First, limestone, silica source such as silica sand and serpentine, fine coke and remineralization are blended with iron ore powders of multiple brands cut out from the raw material tank, and the blended raw materials are hydrolyzed and granulated with a drum mixer, and then Dwyroid type. Sintered in a sintering machine to form a sinter cake. The sinter cake discharged from the sintering machine is crushed and sized, and usually 5 mm or less is circulated to the raw material as returned ore, while 5 mm or more is transported as a product to the blast furnace process.

[0003] On the other hand, the quality control of the sinter ore is performed by variously controlling the sinter ore production process on the basis of the results obtained by measuring the various qualities of a part of the product sinter sampled during transportation in a separate process. It is implemented by that. Specifically, in adjusting the reducibility, the RI index obtained by the method specified in JIS,
Or, using the FeO chemical analysis value as a control index, adjust the amount of coke breeze and the ore brand so that it is within the target range. In the adjustment of the reduction pulverizability, the RDI index or the With the Al ₂ O ₃ chemical component as a control index, the particle size of the limestone or silica source is adjusted or the ore brand is changed so that it falls within the target range. In the adjustment of cold strength, the rotational strength index (TI) or After measuring the drop strength index (SI), it is common to adjust the amount of coke breeze or the ore brand so that it falls within the target range.

[0004]

In the conventional quality measuring method, at most the chemical components, RDI, and cold strength index (T
I and SI) are every 4 hours and RI is every 6 hours, so it was difficult to quickly adjust the operation.

On the other hand, JP-A-61-110726, JP-A-63-10138, and
JP-A-10-1738 discloses a method for evaluating the sintering degree, yield, and productivity of a sinter from a tomographic image of a sinter cake obtained online using a CT scanner. There has not been a method for evaluating the reduced powderability and reducibility of the sintered ore from the tomographic image of the layer.

The present invention provides a method for evaluating the reduced powderability and reducibility of a sinter from a CT image of a sinter packed bed, thereby enabling quick control of the sinter quality.

[0007]

According to the present invention, a cross section of a sintered packed bed is imaged with a CT scanner, a region where coke in the raw material is burning is determined from the cross section, and the porosity and the porosity in the region are determined. Determining a mean pore diameter, and adjusting the particle size of one or both of coke breeze and limestone to be mixed with the sintering raw material so that the porosity and the mean pore diameter fall within predetermined ranges. It is a manufacturing method of.

According to the present invention, relatively fine pores associated with the combustion and extinction of coke breeze in the early stage of the sintering process remain as fine pores in the product sinter, which reduce the reducibility of the sinter to powder and reduce Paying attention to the strong influence on the properties, it detects and quantifies fine pores by dynamic CT measurement in the sintering process and uses it for quality control.

It is to be noted that the region where the coke is burning is defined as a region within a range of 30 to 120 seconds after the start of the image of the state of the initial blended raw material, and RI and R.
This is preferable in that a good relationship with DI can be obtained. In addition, the position in the layer height direction when setting the region is usually 400 to 60.
For a layer thickness of 0 mm, the upper layer 100 mm and the lower layer 100
It is preferable to use an intermediate portion excluding mm because a good estimation can be made. The predetermined range of the porosity and the average pore diameter is a range of the porosity and the average pore diameter corresponding to the quality control standard value imposed on each sintering machine. Specifically, FIGS. There is a relationship as illustrated.

[0010]

FIG. 4 shows a typical change in the pore structure during the sintering process as a time change of the porosity, the average pore diameter, and the shape factor of the pore at a certain layer height position. This is CT
It has been clarified by dynamic tomographic observation by a scanner, and the whole is composed of four stages. The first stage is a state of the compounding raw material before sintering is started, and the porosity is 40%.
It is composed of a group of fine spherical pores of about 2 to 3 mm. Second
The stage corresponds to a heating period during the burning of coke breeze, and while the porosity increases to about 50% and the average pore diameter also increases to 4 to 5 mm, the shape is still in a state close to a sphere. I have. The third stage corresponds to a state where the coke breeze is kept at a high temperature even after the completion of the combustion. The change in the porosity is reduced, but the pore diameter is further increased, and the shape is flattened. The fourth stage is a state in which the progress of sintering is stopped after the cooling process, and a final sinter cake is obtained.

The mechanism by which the pores formed in the initial stage (first and second stages) affect the quality of the sintered ore will be described below. The pores remaining in the sintered ore are considered to be open pores from the boundary of 2 to 5 mm, and closed pores below it.
In terms of quality, open pores of 5 mm or more determine the strength, while closed pores of 0.5 mm or less govern reducibility. Conventionally, attention has been paid to the productivity, strength, and yield of sintered ore. Therefore, it is considered that pore groups formed after the third stage are important. The method described in Japanese Unexamined Patent Publication No. 63-101738 covers the open pores of the sinter cake, and the method described in Japanese Unexamined Patent Publication No. 3-10138 covers the third stage, specifically, the variation of the open pores limited to 10 mm or more. It is what it was. However, if attention is paid to the reduction properties of the sintered ore, it is too large, and the pores formed in the second stage are important. The present inventors have found that some of the pores observed in the second stage (which are presumed to be fine but open pores in the second stage) are taken into the product sinter in the subsequent third stage to form closed pores. It was noted that it remains and that it has a good relationship with reduced powderability and reducibility as described below. Then, the initial relatively fine pore structure observed in the second stage is measured using a tomographic image by a CT scanner, and is used for controlling RI and RDI.

FIGS. 5 and 6 show specific examples of the relationship between the pore structure and quality in the second stage. FIG. 5 shows 30 to 12 after the start of image change.
The relationship between the porosity and the RI is shown using the average pore diameter obtained based on the image of the region of 0 second as a parameter. If the average pore diameter is the same, the larger the porosity, the more the porosity becomes the same. If there is, the smaller the average pore diameter, the higher the RI. FIG. 6 shows the porosity, the average pore diameter and the RDI as in FIG.
The tendency is the same as that of RI.

The reason why the porosity and the average pore diameter in the second stage can be controlled by adjusting the particle size of limestone and / or coke breeze will be briefly described. The coke breeze is a substance that just burns and disappears in the second stage to form pores, and the pores can be controlled by the size of the particles before burning. Also,
Limestone is thermally decomposed at around 900 ° C., but it is considered that it shrinks somewhat at this time and forms fine pores. Therefore, the porosity and the average pore diameter in the second stage can be controlled also by adjusting the particle size of the limestone.

As shown in FIG. 1, a method of imaging a cross section of a sintered packing layer by a CT scanner is such that an X-ray generator 4 rotating around a pallet 1 of a sintering machine and an X-ray detector 5 are installed facing each other. Although there is a method of directly taking an image, a large facility is required. Therefore, as shown in FIG. 2, the raw material after granulation is sampled before being charged into the sintering machine, and the vertical section is imaged by the CT apparatus while firing in the sintering pot 6 under the same conditions as the actual machine. You may. The area where coke breeze is burning refers to an area corresponding to 30 to 120 seconds after the start of the change of the image of the raw material state. Furthermore, it is more preferable to obtain the porosity and the average pore diameter for each of a plurality of vertical cross sections in which this region exists in an intermediate portion excluding the upper and lower portions of the packed layer by 100 mm, and to obtain the average value. Further, an apparatus having a configuration for capturing a horizontal cross-sectional image as shown in FIG. 3 can also be used. The image corresponding to the area where coke breeze is burning when capturing a horizontal cross section is a horizontal cross-sectional image continuously captured at a certain time interval, from the time when the change starts from the continued state of the initial raw material state. 30-1
It is sufficient to use one or several average images of horizontal cross-sectional images taken during 20 seconds.

[0015]

[Embodiment 1] An example in which the management of RI is carried out by adjusting the particle size of coke breeze will be described. In the actual machine operation, RI was compared between the conventional method with a frequency of once / day and the method of the present invention for imaging the horizontal cross section shown in FIG. 3 with a frequency of 6 times / day. RI
Was set to 66.

Specifically, a blended raw material sampled from an actual machine before the pallet of the sintering machine was obtained was collected by using a 500 mm height × 90 mm diameter.
0.5 Nm / sec using a quartz sintering pan 6 mm
While suction sintering is performed, the horizontal section of the packed bed is continuously imaged at intervals of 20 seconds, and four images captured 40 to 120 seconds after the tomographic image starts to change from the initial raw material filling state are also shown. Then, the average pore diameter and porosity were determined.

In the conventional method, the actual measurement result of RI is compared with a target value, and when the RI value is higher than the target value, the coke breeze is made coarser, and when the RI value is lower, finer coke is adjusted. on the other hand,
In the method of the present invention, when the RI value estimated from the average pore diameter and the porosity obtained by the CT scanner according to FIG. 5 is higher than the target value, the coke breeze particle size is coarsened, and when the RI value is low, it is finely adjusted. The results of the average pore diameter and the porosity at the time of the RI evaluation were 2.5 ± 0.3 mm and 35 ±, respectively.
It changed in the range of 3%.

As a result of the comparison of the change in the variation of the RI shown in FIG. 7, it was found that the quality control process capability was improved because the measurement frequency was increased and the adjustment action was increased.

[0019]

[Second Embodiment] An example in which RDI is managed by means of limestone particle size adjustment will be described. In a real machine operation, the conventional method with a frequency of 6 times / day was compared with the method of the present invention for imaging the horizontal cross section shown in FIG. 3 with a frequency of 6 times / day. The RDI management target value was 35 in each case.

In the conventional method, the result of the RDI is compared with the target value, and when the RDI value is higher than the target value, the limestone is coarsened, and when the RDI value is lower, the limestone is finely adjusted. On the other hand, in the method of the present invention, when the RDI value estimated according to FIG. 6 from the average pore diameter and the porosity obtained by the CT scanner is higher than the target value, the limestone is coarsened, and when the RDI value is low, it is finely adjusted. . The results of the average pore diameter and the porosity at the time of the RDI evaluation changed in the ranges of 2.2 ± 0.3 mm and 33 ± 3%, respectively.

As a result of the comparison of changes in the RDI shown in FIG.
In the method of the present invention, the time delay of the results was about half a day in the conventional method, but was eliminated in the method of the present invention.

[0022]

According to the present invention, since the quality of the sinter can be predicted very quickly, an appropriate operation action can be performed in a timely manner, so that the quality process control ability is remarkably improved.

[Brief description of the drawings]

FIG. 1 is a view showing a method of imaging a vertical cross section of a sintering packed layer by a CT scanner on a sintering machine strand of the present invention.

FIG. 2 is a diagram illustrating a method for imaging a vertical cross section of a sintered filling layer using a CT scanner offline according to the present invention.

FIG. 3 is a diagram illustrating a method for imaging a horizontal section of a sintered filling layer using a CT scanner offline according to the present invention.

FIG. 4 is a diagram showing a concept of a change in pore structure during a sintering process.

FIG. 5 is a diagram showing the relationship between the pore structure and JIS-RI in the second stage.

FIG. 6 is a diagram showing a relationship between a pore structure and RDI in a second stage.

FIG. 7 shows JIS-RI and R according to the conventional method and the method of the present invention.
It is a figure which shows the comparison of the fluctuation range of DI.

[Explanation of symbols]

 Reference Signs List 1 sintering machine pallet 2 wind box 3 wind leg 4 X-ray generator 5 X-ray detector 6 sintering pot 7 rotating stage 8 sintering packed layer

Claims (1)

[Claims] An image of a cross section of the sintered packed bed is taken by a CT scanner, a region where coke in the raw material is burning is determined from the cross section, and a porosity and an average pore diameter in the region are obtained.
A method for producing a sintered ore, comprising adjusting the particle size of one or both of coke breeze and limestone to be mixed with a sintering raw material such that the porosity and the average pore diameter are within predetermined ranges.