JPH10265857A - High quality sintered ore - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide sintered ore excellent in both of reducibility and reduced powdering resistance. SOLUTION: The sintered ore having the chemical components of <=5 wt.% SiO2 content and in the range of 1.0-3.0 basicity shown width CaO (wt.%)/SiO2 (wt.%) and average constituting ore structure satisfying the equation (hematite phase quantity (area %))/(magnetite phase quantity (area %)) <=0.5 and >=1.5 area % of the average containing porosity, is produced. The ratio of the possessive area in the sintered ore of opened pores having virtual diameters of 10-100 μm to the possessive area in the sintered ore of the total opened pores, is made to >=30%. Slag content with chemical analysis is made to <=1.2 wt.%. The sintered ore excellent in RI and RDI can be provided while reducing the fuel ratio and the slag ratio in a blast furnace and executing the stable operation of extra-high PCI without specially supplying and adjusting iron ore raw material and auxiliary raw material.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-quality sintered ore having excellent quality characteristics in both reducibility and resistance to pulverization.

[0002]

2. Description of the Related Art Sinters used as blast furnace raw materials are generally produced by the following method. First, iron ores unloaded from the Vessel are piled up in the ore yard for each brand. Thereafter, it piled various powder ore, containing CaO auxiliary material, containing SiO ₂ auxiliary material, sintering dusts and carbonaceous material such as, mixed by bedding method at a rate that is set in advance, and blending powder. This blending powder and limestone,
Each raw material such as quicklime, quartzite and / or serpentine, coke breeze and / or anthracite, and ore return, and in some cases, even plain ore, is put into each mixing tank, and a predetermined amount of raw material is supplied from each mixing tank.・ Continuously cut out auxiliary materials. An appropriate amount of water is further added to these raw materials and auxiliary raw materials, mixed, and granulated.

[0003] The sintering raw material thus granulated, that is, pseudo particles, is continuously transferred from a hopper onto a pallet of an endless moving great type sintering machine (Dwyroid type sintering machine) with a height of about 500 to 700 mm. To be layered. Next, the carbon material in the surface portion is ignited by the ignition furnace, and the carbon material is burned while forcibly sucking air downward. The pseudo particles are sintered and agglomerated by the combustion heat generated at this time.

After cooling the thus-produced sintered cake,
After crushing and sizing, particles having a size of 3 to 5 mm or more are charged into a blast furnace as a product sintered ore. 3 generated during crushing and sizing process
The fine powdered ore having a diameter of 5 mm or less is reused as a part of the raw material for sintering.

On the other hand, as the quality characteristics of the sinter, cold strength, reducibility, reduction resistance to pulverization, etc. are particularly important and have a great effect on the stable and efficient operation of the blast furnace. Have been. As the evaluation method of the above characteristics, the cold strength is JIS method tumbler strength (TI), JIS method drop strength (SI), etc., the reducibility is JIS reduction rate (RI), and the reduction powdering resistance is the Japan Iron and Steel Association. The reduced powder index (RDI) of the Ironmaking Subcommittee method is used. Further, from the viewpoint of the production cost of the sinter, it is required that the unit consumption of energy such as carbonaceous material, gas, and electric power be low, and that a high production rate and a high yield be obtained. Furthermore, recently, in response to the environment and energy saving, there is a demand for minimizing slag as a by-product generated in a blast furnace. Against this background, a number of techniques have been proposed for improving the quality, production rate, yield, and the like.

Generally, as a method of improving the RI and high-temperature properties (such as high-temperature load softening properties) of sinter, reduction of the slag content in the sinter and, therefore, reduction of the SiO ₂ content are effective. Is known to be relevant. However, in such a case, mutually opposite effects such as deterioration in cold strength, yield and RDI appear. Therefore, R
Many difficult problems must be solved in order to produce high-quality sintered ore by improving the properties and high-temperature properties. Also,
Furthermore, with the recent development of blast furnace high PCI (pulverized coal injection) operation technology, low SiO ₂ sintered ore with a small amount of slag is required especially for achieving air permeability, liquid permeability, and stable operation in the lower part of the blast furnace. It is gaining attention as an indispensable raw material.

As a technique aiming at quality improvement by low SiO ₂ , for example, Japanese Patent Publication No. Sho 58-1180 discloses that the production rate is not reduced by adjusting the particle size of silica to be added to the sinter to less than 1 mm. Discloses a method for reducing SiO ₂ in sinter (Prior Art 1). However,
In the prior art 1, slag-making raw materials such as silica stone and limestone must be finely pulverized, and an increase in cost due to pulverization is inevitable. Furthermore, since it is presumed that silica is added as a slag-making material, the SiO
_This is an unsuitable technology for producing sintered ore of extremely low SiO ₂ by not adding an SiO ₂ source without actively adding other than ₂ .

Japanese Patent Publication No. 52-721 discloses a method for suppressing the deterioration of RDI due to low SiO ₂ by adding fine Ni slag generated during Ni smelting as a raw material for preparing pseudo particles. Technique 2) is disclosed. However, also in this method, it is necessary to procure an unnecessary slag material and adjust it to a predetermined form and particle size before adding it.

Japanese Patent Application Laid-Open No. 5-59972 discloses a technique for producing a low SiO ₂ sintered ore by special adjustment of a porous low SiO ₂ ore containing goethite and a CaO-containing auxiliary material. 3) is disclosed. However, as in this technology, it is difficult in terms of ore supply and demand to use a specific ore brand to perform stable operations over a long period of time.

[0010]

As described above, in order to improve the RI and RDI without deteriorating the sintering operation, the prior art procures special raw materials and auxiliary raw materials,
There is a problem that they must be adjusted in a pretreatment or other special steps, and it cannot be said that this is a versatile radical improvement technique.

It is an object of the present invention to provide a sinter having an SiO ₂ content of 5 wt.% Or less, without special procurement and adjustment of the above-mentioned iron ore raw materials and auxiliary raw materials, An object of the present invention is to provide a high-quality sinter which is excellent in any reduction powdering resistance.

[0012]

Means for Solving the Problems From the above-mentioned viewpoints, the present inventors have focused on the following points in developing a high-quality sintered ore.

[0013] In order to improve the reduction powdering resistance of the sinter in the blast furnace, the hematite in the sinter is 500 to 6%.
It suppresses volume expansion when it is reduced in the temperature range of 00 ° C. and changes into magnetite. For that purpose, reduce the amount of hematite phase in sinter and increase the amount of magnetite phase.

In the above, increasing the amount of the magnetite phase reduces the reducibility of the sinter, which is not only prevented from being reduced. Increasing the porosity to an appropriate value or more. More preferably, the size distribution of the contained pores is adjusted to be within an optimum range.

In order to further enhance the reducibility,
To further reduce the amount of slag in sinter. The present invention has made intensive studies based on the above viewpoints. As a result, as a particularly remarkable feature, by giving an appropriate range for each of the value of the ratio of the amount of the hematite phase and the amount of the magnetite phase, and the porosity contained, the reduction in powdering resistance and reducibility is reduced. In both cases, it was found that excellent high quality sinter was obtained.
The present invention has been made based on the above findings.

The high-quality sinter of claim 1 is SiO ₂
The content is 5 wt.% Or less, and CaO (wt.%) / SiO ₂
It has a chemical component whose basicity expressed in (wt.%) Is in the range of 1.0 to 3.0, and has a formula: (amount of hematite phase (area%) / (amount of magnetite phase (area%)) It is characterized by having an average constituent mineral structure satisfying ≦ 0.5 and having an average content porosity of 15 area% or more.

The high-quality sintered ore according to the second aspect is the first aspect.
The feature of the described sinter is further characterized in that the ratio of the volume occupied by the open pores having a virtual diameter of 10 to 100 μm in the sinter to the volume occupied by the open pores in the sinter is 30% or more. It is characterized by the fact that the pore size distribution is added.

The high-quality sintered ore according to the third aspect is the first aspect of the invention.
The slag content based on chemical composition analysis is 12 wt.

[0019]

Next, an example of an embodiment of the present invention will be described. First, a manufacturing method will be described.

FIG. 1 is a schematic view showing an example of a production flow of the sintered ore of the present invention. As raw materials, various piled iron ores (fine ores) 1a,..., 1n, limestone 2 and quick lime 3, returned ore 4, silica stone 5, and coke breeze 6 (only when coke breeze is installed) Cut out each of
The materials are weighed by a measuring device 7 and a raw material having a predetermined mixing ratio is charged into a primary mixer. Here, moisture 8 'is added and adjusted and mixed. The conditioned and mixed ingredients are granulated by the secondary mixer 9 or the pelletizer 10 to prepare pseudo particles.
In the case where the coke breeze is packaged into pseudo particles, the coke breeze 6 'is packaged by the coating mixer 11 continuously. Next, a granulated product having an average particle size of about 2 to 8 mm is charged into the sintering machine 12. The upper surface of the granulated material charged into the sintering machine 12 is ignited, and sintering proceeds by downward suction to produce a sintered ore.

In the process of producing the sintered ore, SiO ₂
When the content is 5 wt.% Or less, CaO (wt.%) / SiO ₂ (w
t.%) within the range of 1.0 to 3.0, and the slag content is adjusted to 12 wt.% or less. It is adjusted by an ordinary method using the mixing ratio of these raw materials.

In the firing process, the reducing gas 13 is supplied to a firing furnace to increase the amount of magnetite phase in the sintered ore and adjust the ratio of the amount of hematite to the amount of magnetite to 0.5% or less in terms of area%. (Part of the sintering machine 12, not shown) Blow from above. In addition, in order to secure the amount of magnetite phase, it is necessary to mix magnetite-based ore and use Fe
It is also effective to mix a high-FeO raw material containing a large amount of O or increase the mixing ratio of powdered coke for fuel. However,
When coke breeze is added and mixed, excess melt is generated in the sintered layer at a low cost, and it tends to be difficult to secure a predetermined porosity. Therefore, in the production of the product of the present invention, in order to ensure the average porosity of 15 area% or more, it is desirable to minimize the amount of added coke breeze and limit it to 42 kg / ton-product or less.

The volume of the fully open pores is 10 to 100 μm.
In order to increase the ratio of the volume sum of the open pores having a virtual diameter of m, among the prepared various iron ores, increasing the content of a high content of gas generating components such as moisture, increasing the SiO ₂ content The raw material composition is appropriately combined with reducing the slag content and reducing the coke breeze content.

The high-quality sintered ore of the present invention is manufactured by the above-described manufacturing method. In the present invention, the reason why the chemical composition, the average mineral structure, the average porosity and the like of the sintered ore are limited as described above will be described below.

(1) SiO ₂ content ≦ 5 wt.% Regarding the amount of slag which is a by-product generated in the blast furnace, particularly from the viewpoint of environmental protection and energy saving, gangue in fine ore further supplied to the blast furnace manufacturer In order to cope with the tendency for the content to decrease, it is desired to reduce the amount of slag contained in the sintered ore as much as possible. In order to respond to this, assuming that the basicity of the sinter is kept within a predetermined range,
It is necessary to reduce the SiO ₂ content of the sinter. Further, SiO ₂ in the sinter increases the amount of the slag melt, and particularly reduces the reducibility. Therefore, SiO _{2 in} the sinter
The content is limited to 5 wt.% Or less. More preferably, it is 4.5.
It is better to be less than wt.%. Reducing the SiO ₂ content in this manner can be achieved by reducing the content of firelite (2F
It also has the effect of suppressing the generation of hard-to-reduce substances such as eO.SiO ₂ ). Although the lower limit of the SiO ₂ content depends on the types of the main raw material and the auxiliary raw material, it is basically determined in conjunction with the basicity and the slag content. The basicity is set in the range of 1.0 to 3.0 as described in the next section, and the slag content is set in the range of the basicity of ordinary sintered ore, for example, about 5 to 20 wt.%. Is appropriate.

(2) Basicity: CaO (wt.%) / SiO ₂
(Wt.%) = 1.0-3.0 In order to secure the strength of the sintered ore, it is effective to increase the basicity. However, if the basicity is too large, the so-called weather resistance, which mainly powders during yard stock, deteriorates. Therefore, the strength of the sinter is secured, and the basicity of the sinter that is practical as a blast furnace charge is 1.0 to
It should be limited to a range of 3.0.

(3) To have an average constituent mineral structure that satisfies hematite phase amount (area%) / magnetite phase amount (area%) ≦ 0.5. This condition is one of the two most important requirements in the present invention. In order to improve the reduction powdering resistance of the sinter, it is effective to lower the content of the hematite phase and increase the magnetite content in the mineral structure constituting the sinter. However, if the area% of the average value (average porosity) of the results of measuring the porosity in a large number of fields is less than 15%, the reducibility of the sinter at around 900 ° C. is improved to a high level. Is not enough. However, when the average value (average constituent mineral structure) of the area% ratio between the amount of hematite phase and the amount of magnetite phase when the mineral structure is observed and measured in a sufficiently large number of visual fields exceeds 0.5, the temperature of 500 to 600 ° C. It is insufficient to improve the reduction pulverization resistance in the temperature range to a high level.

On the other hand, the smaller the area% ratio between the amount of the hematite phase and the amount of the magnetite phase is, the more the resistance to reduction powdering is improved. However, if this value is too small, the increase and maintenance of the porosity content, which is another important means in the present invention, for suppressing the reduction of the reducibility due to the increase in the amount of the magnetite phase, the upper limit is set. You have to make it bigger. The reason is that if the porosity of the sintered ore is about 50% or more in terms of area%, the strength of the sintered ore is insufficient for practical use. For these reasons, in order to maintain the reducibility at a high level, it is desirable to limit the area% ratio between the amount of the hematite phase and the amount of the magnetite phase to about 0.1 or more.

As described above, the sintered ore of the present invention should be limited to the one in which the ratio of the area percentage between the amount of hematite phase and the amount of magnetite phase is adjusted to 0.5 or less with respect to the average constituent mineral structure. .

(4) Average porosity (area%) ≧ 15% This condition is another one of the two most important requirements in the present invention. In order to improve the reducibility of the sinter, it is better to increase the content of open pores formed in the surface of the sinter per unit weight of the sinter. There is a certain correlation between the open porosity and the porosity based on the area% that appears on the cut plane. Therefore, in the present invention, for convenience of measurement, the porosity based on the area% is employed instead of the open porosity. In order to improve the reducibility of sinter,
It is effective to increase the porosity (content porosity) on an arbitrary cross section of the sintered ore. However, the average value of the measurement results of the contained porosity in a number of visual fields (average contained porosity)
If the area% is less than 15%, it is not enough to improve the reducibility of the sintered ore at around 900 ° C. to a high level.

On the other hand, the larger the porosity, the more the above-mentioned reducibility increases. However, when this value is too large, the strength of the sintered ore is insufficient for practical use, as described in the above section (3). In order to keep the sintered ore sufficiently strong for practical use, the porosity of the sintered ore is set to 50% by area%.
% Or less.

As described above, the sintered ore of the present invention should be limited to the one whose average porosity (area%) is adjusted to 15% or more. In the above description, the amount of the hematite phase and the amount of the magnetite phase are indicated by area% with respect to the composition ratio of the mineral structure of the sintered ore, and the porosity content is also indicated by area%. It is defined as the area% measured on the plane cut by the sinter. The reason for this definition is that, at present, as a method capable of measuring each of the above quantities with high accuracy, for example, the area%
Because it is better to ask for On the other hand, it is possible to convert the area% to the volume% geometrically by a known calculation formula. Therefore, the above-mentioned area% in the present invention is effective even when converted to volume% by using a method capable of measuring with high accuracy.

(5) The ratio of the volume sum of the open pores having the virtual diameter of 10 to 100 μm to the volume sum of the fully open pores is 30% or more. The reduction reaction of the sinter in the blast furnace is performed by contact of the reducing gas in the blast furnace with the exposed surface of the sinter and gas diffusion into the sinter. The reaction mainly depends on the contact area. Therefore, the higher the open porosity, the better the reducibility of the sintered ore. However, if the entrance diameter of the open pores is too small, the entrance of the open pores is closed due to the process of transferring the sinter or load in the blast furnace. The inlet diameter of the open pore can be considered to be proportional to the virtual diameter. Here, the virtual diameter of the open pore is defined to indicate the diameter of the sphere when the volume of the open pore is assumed to be the volume of the sphere. The virtual diameter can be measured using, for example, a commercially available mercury intrusion porosimeter. According to the experimental results of the present inventors, when the open porosity is constant, the reducibility of the sinter is determined by the ratio of the volume sum of the open pores having a virtual diameter of 10 to 100 μm to the volume sum of all the open pores. It was found that it increased as the number increased. And the ratio is 30%
Above, the reducibility is remarkably improved. Further, since the volume ratio of the open pores having a virtual diameter of 10 to 100 μm does not become too large, and the strength of the sinter does not decrease, there is no need to set an upper limit.

(6) Slag content ≦ 12 wt.% In the present invention, the slag content of the sinter refers to the total amount of Fe oxides and components other than Fe based on chemical composition analysis, and the slag content based on image processing. Not a percentage. Reducing the slag content in the sinter increases the reducibility,
When the content is not more than wt.%, the reducibility is further improved. Therefore, the quality of the sintered ore of the present invention is further improved. In addition, when the slag content is too low, the reduction in strength becomes a problem. Therefore, it is desirable to secure a slag of such a degree that the strength is not a problem, for example, about 5 wt.%.

[0035]

Next, the high-quality sintered ore of the present invention will be described in more detail with reference to examples. According to the production flow of the sintered ore shown in FIG.
6) and sintered ores outside the scope of the present invention (conventional methods and Comparative Examples 1 to 5) were produced. However, the coke breeze was contained in pseudo particles.

Tables 1 and 2 show the raw material composition of each Example, conventional method and Comparative Example, respectively. Table 3 shows the composition of each iron ore used. As shown in Tables 1 and 2, the target value of the SiO ₂ content of the sintered ore was set to various values between 3.0 and 5.0 in the examples according to the above-described conventional raw material blending. In Comparative Examples, various values were set between 4.2 and 5.5. On the other hand, the target value of the basicity (CaO / SiO ₂ ) was a constant value of 2.0 for all of the examples, the conventional method, and the comparative example. Further, in the embodiment, the target value of the porosity of the sinter is adjusted to various values of 15 area% or more by the blending amount of iron ore and the blending amount of coke fine in consideration of the moisture content in the iron ore, Care was taken to ensure that the ratio of those with relatively small virtual diameters was somewhat high.

[0037]

[Table 1]

[0038]

[Table 2]

[0039]

[Table 3]

On the other hand, in the test production process of the sintered ore, in the case of the examples, a part of the hematite phase in the pseudo particles was reduced to magnetite by blowing a reducing gas from the upper part of the firing furnace in the firing process. Table 4 shows the components of the reducing gas used and the blowing conditions. On the other hand, in the case of the conventional method and the comparative example, the blowing of the reducing gas was not performed in the firing process.

[0041]

[Table 4]

For each of the sintered ores obtained under the above production conditions, the SiO ₂ content and the basicity (CaO / S
iO ₂ (wt.% ratio), the composition ratio of the mineral structure of the hematite phase and the magnetite phase, the porosity, the distribution of the pore diameter, and the slag content were tested.

The composition ratio of the mineral structure of the hematite phase and the magnetite phase can be determined by observing the mineral structure of the cut and polished surface of the sintered ore with a reflection microscope, identifying the hematite phase and the magnetite phase, and performing image processing on the basis of the identification. The phase was quantitatively analyzed to determine (amount of hematite (area%)) / (amount of magnetite phase (area%)), and the ratio was expressed as a value.

The porosity was measured by image processing of the cut and polished surface of the sintered ore. Image processing is performed on the polished surface
An area of 100 μm square per area was measured at an arbitrary 1,000 points, and the average porosity was determined and expressed as area%.

The distribution of the pore diameter was measured using a commercially available mercury intrusion porosimeter, and a predetermined diameter was determined from the virtual diameter of the open pores determined depending on the applied mercury pressure and the amount of mercury injected into the open pores at that time. The ratio of the volume occupied by the open pores having a virtual diameter within the range in the sinter ore to the volume occupied by the open pores in the sinter was determined and expressed as%.

Tables 5 and 6 show the results of the above measurements for the example, the conventional method and the comparative example, respectively. Also,
Tables 7 and 8 show the chemical analysis results of the sintered ore of the example, the conventional method, and the comparative example, respectively.

[0047]

[Table 5]

[0048]

[Table 6]

[0049]

[Table 7]

[0050]

[Table 8]

As can be seen from Table 6, in the conventional method and Comparative Examples 1 to 5, the content of SiO ₂ , (amount of hematite phase (area%)) / (amount of magnetite phase (area%)), and average porosity At least one is outside the scope of the present invention. In contrast, as can be seen from Table 5, Example 1
6 to 6 satisfy the conditions of claim 1 of the present invention, Examples 4 to 6 satisfy the conditions of claim 2, and Example 5
And 6 satisfy the condition of claim 3.

FIG. 2 and FIG.
Typical operation results for the conventional method and each comparative example
(Production rate and product yield) and strength properties of sinter
(TI ₊₁₀), Reducible (JIS-RI) and reduction resistant powder
3 shows the test results of chemical conversion (RDI).

The following matters can be seen from FIGS. In each of the conventional method and the comparative example which are out of the scope of the present invention, at least one of the reducibility and the reduction powdering resistance of the sintered ore is inferior, and none of them are excellent. .

On the other hand, the sintered ore of the present invention is excellent in all of the strength properties, reducibility and resistance to reduction powdering of the sintered ore. Moreover, the production rate and the product yield are excellent. That is, it can be seen that in the production of the sintered ore of the example, the operation is stabilized at a high level, and a product having excellent quality can be obtained.

[0055]

As described above, according to the present invention,
Without special procurement or adjustment of iron ore raw materials and auxiliary raw materials, while further reducing the fuel ratio of the blast furnace, reducing the slag ratio, and stably operating ultra-high PCI, we can produce sintered ore with excellent RI and RDI. And an industrially useful effect is provided.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of an example of a production flow of a sintered ore of the present invention.

FIG. 2 is a graph showing a typical operation result of an example, and a test result of strength characteristics, reducibility and reduction powdering resistance of a sinter.

FIG. 3 is a graph showing typical operation results of a conventional method and a comparative example, and test results of strength characteristics, reducibility, and reduction powder resistance of a sintered ore.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Raw material 1a, ... 1n Various iron ores 2 Limestone 3 Quick lime 4 Returning mineral 5 Silica 6 Coke powder 6 'Coke powder 7 Meter 8 Primary mixer 8' Moisture 9 Secondary mixer 10 Pelletizer 11 Coating mixer 12 Sintering Machine 13 Reducing gas 14 Blower

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Noboru Sakamoto 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Nihon Kokan Co., Ltd. (72) Inventor Hideaki Sato 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Sun (72) Inventor Takashi Watanabe 1-2-1 Marunouchi, Chiyoda-ku, Tokyo Nihon Kokan Co., Ltd.

Claims (3)

[Claims] 1. The method according to claim 1, wherein the content of SiO ₂ is 5 wt.
It has a chemical component having a basicity represented by aO (wt.%) / SiO ₂ (wt.%) in the range of 1.0 to 3.0, and has the following formula (1): (Area%)) / (Amount of magnetite phase (Area%)) ≦ 0.5 ------------------- (1) It has an average constituent mineral structure and 15 areas A high-quality sintered ore having an average porosity of not less than 10%. 2. The sinter of claim 1, further comprising:
The ratio of the volume occupied by the open pores having a virtual diameter of 100 μm in the sinter to the volume occupied by the fully open pores in the sinter is 3
A high-quality sintered ore characterized by adding 0% or more. 3. A high quality sintered ore according to claim 1, further comprising a slag content of 12 wt.% Or less based on chemical composition analysis.