JP6780779B2 - Sintered ore manufacturing method - Google Patents

Description

The present invention relates to a method for producing a sinter for the purpose of improving the strength of the sinter as a raw material for a blast furnace.

The blast furnace used in the iron manufacturing industry uses lump ore and sinter as the iron source. The iron source is melted and reduced by inserting the blast furnace raw material containing the iron source from the upper part and blowing the reducing gas from the lower part. It is a facility to do. In order to promote the reaction between the reducing gas and the iron source, it is necessary for a sufficient amount of gas to flow in the blast furnace, and improving the air permeability in the furnace will improve the production rate of hot metal and reduce costs. Is important.
In order to improve the air permeability in the blast furnace, it is necessary to suppress the powder ratio (5 mm or less) of the blast furnace raw material, and it is desired to use a high-strength blast furnace raw material in order to reduce the powder ratio. For this reason, various methods have been implemented to improve the strength of sinter, which is the main raw material.

Conventionally, for example, the method shown in Patent Document 1 is known as a method for producing a sinter for improving the strength of the sinter.
The method for producing sinter shown in Patent Document 1 is a method for producing sinter by supplying various gas fuels from the charging layer of the sinter raw material deposited on the pallet of the sinter. As the gas fuel supplied from above the charging layer on the pallet, a gas fuel diluted to the combustion lower limit concentration or less is used, and when the gas fuel is supplied and sintered, the supply position and the charging layer are the highest. The sinter is produced by adjusting either one or more of the ultimate temperature and the holding time in the high temperature range.
By this method for producing sinter, in the operation of the downward suction type sinter, by supplying diluted gaseous fuel into the charge layer, high strength is achieved without deteriorating the air permeability of the entire charge layer. Sintered ore can be produced at a high yield.

Further, as another example of a method for producing a sinter for improving the strength of the sinter, conventionally, for example, the one shown in Patent Document 2 is also known.
The method for producing sinter shown in Patent Document 2 is a method for producing sinter using high crystalline water ore as a raw material, in which dromite is used as an MgO source and sinter as an auxiliary raw material, and the lower layer of the pallet of the sintering machine is used. Dolomite is preferentially distributed to the parts and fired.

Further, as another example of a method for producing a sinter for improving the strength of the sinter, conventionally, for example, the one shown in Patent Document 3 is also known.
The method for supplying sinter to the blast furnace shown in Patent Document 3 is performed once or multiple times in advance or in the middle of the transport path in the transport path of the sinter from the sinter excretion section to the charging into the blast furnace. A total of 200 to 600 J / kg of impact energy is applied separately, and then the sinter is classified.

Japanese Unexamined Patent Publication No. 2008-95170 Japanese Unexamined Patent Publication No. 2000-336434 Japanese Unexamined Patent Publication No. 2000-336434

However, even in the sintered ore produced by the conventional methods for producing the sintered ore shown in Patent Document 1 and Patent Document 2, a portion having a low strength is partially included, and the overall strength is lowered. There was a problem.
Further, in the case shown in Patent Document 3, control is performed by impact energy, but for sinter, which is a brittle material, crushing does not proceed even if a small impact energy is applied, and the strength of the sinter There was a problem that it was difficult to obtain improvement.
Therefore, the present invention has been made to solve this problem, and an object of the present invention is to provide a method for producing a sinter in which a portion having a low strength is partially removed and the overall strength is improved. It is in.

In order to achieve the above object, the method for producing a sinter according to one aspect of the present invention applies an impact force to the sinter after the primary crushing, and then sifts the sinter given the impact force. The gist is that.

According to the method for producing a sinter according to the present invention, an impact force is applied to the sinter after the primary crushing, and then the impacted sinter is sieved to partially increase the strength. It is possible to provide a method for producing a sinter in which the low portion is removed and the overall strength is improved.

It is a diagram schematically showing a sinter, (A) is a schematic view showing a state in which a sinter is cracked, and (B) is a schematic view in a state where a fragile portion is formed in the sinter. It is a figure which shows the flow of the manufacturing method of the sinter which concerns on one Embodiment of this invention. It is a graph which shows the relationship between the impact force applied to the sinter in the drop method and the drop height. 6 is a graph showing the relationship between the weight percentage for each particle size and the number of drop tests in the drop test of Example 1. 6 is a graph showing the relationship between the weight percentage for each particle size and the number of drop tests in the drop test of Example 2. It is a graph which shows the relationship between the drop strength index increase value in the drop test of Example 1 and Example 2 and the number of drop tests. It is a graph which shows by contrasting the drop strength index when the rotation processing by a rotary drum method is not performed, and the drop strength index when the rotation processing is performed.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. It should be noted that the drawings are schematic, and the dimensional relationship of each element, the ratio of each element, etc. may differ from the realistic ones. Even between drawings, there may be parts with different dimensional relationships and ratios.

First, the inventors considered that the sinter was not uniform, and that both a low-strength portion and a high-strength portion were mixed. For example, as shown in FIG. 1A, there are many cracks 2 and defects that are the starting points of fracture in the sinter 1. Further, as shown in FIG. 1 (B), it is difficult to uniformly sinter not only the crack 2 but also in the firing process, and a large number of fragile portions 3 are formed in terms of structure and structure. Is inevitable. Therefore, the present inventors remove the portions that cause the strength decrease such as the cracks 2 and the fragile portions 3 formed in the manufacturing process in advance before the sinter is completed, and remove the portions having high strength. I came up with the idea of increasing the ratio and increasing the strength of the sinter as a whole.

The present inventors have found that, in order to remove a low-strength portion, the low-strength portion is broken by an external force and separated from the high-strength portion as this method.
Therefore, in the method for producing a sinter according to the present embodiment, an impact force is applied to the sinter 1 after the primary crushing, and then the sinter 1 to which the impact force is applied is sieved. By sieving the impacted sinter 1, it is possible to remove parts such as cracks 2 and fragile parts 3 with low strength, increase the ratio of high-strength parts, and increase the strength of the sinter as a whole. be able to.
Since the sinter that is impacted is the sinter after the primary crushing, the sinter portion of the brittle material is removed by the primary crushing, and even if a small impact energy is applied, it becomes the sinter. Crushing progresses, and the strength of the sinter can be easily improved.

The method for producing the sinter according to the present embodiment will be described. As shown in FIG. 2, first, the sinter 1 is produced in step S101. In the production of this sinter 1, a general method is adopted, and a downward suction type is adopted from raw materials containing CaO such as iron ore powder, limestone and dolomite, granulation aids such as quicklime, and raw materials such as coke powder and smokeless coal. Sinter 1 is produced using the Dwightroid (DL) sinter.
Next, the process proceeds to step S102, and the produced sinter 1 is first crushed. As a result, it is possible to obtain a sinter in which the sinter portion of the brittle material has been removed by primary crushing.
Next, an impact force is applied to the sinter 1 primary crushed in step S102 in step S103.

This impact force is applied to the sinter 1 by the drop method or the rotary drum method. The drop method is a method in which the sinter 1 is dropped from a predetermined height and damaged by acceleration due to gravity and impact with the floor, and is considered to be an effective method for sinter 1 containing iron having a relatively heavy specific gravity. .. Here, any floor material can be used as long as it can withstand impact, but compared to elastic materials such as conveyor belts, highly rigid materials such as metal and ceramic are sinter 1 It was observed that the impact force applied to the bearing was stable and the damage was stable. Further, as a floor material, hard resin has lower rigidity than metal or ceramic, but can reduce the weight, so that it is suitable when the scaffolding for replacement work is narrow. It is also possible to fill a box-shaped container with sinter and drop the sinter 1 onto the sinter, which is suitable when the replacement work is difficult because the floor does not need to be replaced. Further, in the rotary drum method, the sintered ore 1 is put into a rotating rotary drum and a rotation process is performed, and an external force is applied to a portion such as a crack 2 or a fragile portion 3 having low strength multiple times. This is an effective method for destroying the relevant part.

Here, when an impact force is applied to the sinter 1, there is a possibility that even a high-strength portion of the sinter 1 may be destroyed depending on the magnitude of the impact force. Therefore, the magnitude of the impact force on the sinter 1 with respect to the drop height in the drop method was examined.
The impact force P (kgf) was calculated by the following equation (1) using agglomerates and steel materials based on the conventional model.

Here, Κ can be expressed by the following equation (2).

Further, V ₀ : relative velocity at the time of collision (m / s) can be expressed by the following equation (3).

Here, M: mass of sinter (kg), r: radius of sinter (m), ν _S : Poisson's ratio of sinter (−), ν _W : Poisson's ratio of floor (−), E _S: Young's modulus of the sinter (Pa), _{E W:} Young's modulus of the floor (Pa), h: drop height (m), g: acceleration of gravity (Pa). 0.3 As Poisson's ratio [nu _S sinter, using 1GPa as Young's modulus E _S of sintered ore, with physical properties of carbon steel assuming use a steel high strength as a floor, the floor Poisson the ratio ν _W 0.3, the Young's modulus _{E W} of the floor was 210GPa. The radius r of the sinter was generally 2 cm, the density was 3 g / cm ^3, and it was treated as a true sphere.

As a result, as shown in FIG. 3, it can be confirmed that the higher the drop height, the higher the impact force on the sinter 1. It is considered that the strength of the sinter 1 as a raw material for the blast furnace requires an impact resistance of 100 kgf. Therefore, the impact force applied to the sinter 1 must be suppressed to 100 kgf or less. This is because if an impact force larger than 100 kgf is applied to the sinter 1, even a high-strength portion having sufficient strength may be destroyed. With reference to FIG. 3, it can be seen that the drop height must be 2 m or less in order to suppress the impact force applied to the sinter 1 to 100 kgf or less. Therefore, the drop height of the sinter 1 by the drop method was set to 2.0 m or less.

On the other hand, considering the lower limit of the drop height of the sinter 1, the present inventors focused on calcium silicate as a structure having a weak strength in the sinter 1. Calcium silicate is known to be weak among the structures in the sinter 1, and the following documents report that the tensile strength of calcium silicate is 19 MPa.
"Mineral Engineering", ASAKURA PUBLISHING CO. , LTD, 1976, p. 175
Since the tensile strength of this calcium silicate is 19 MPa and the size of the finished product of the sinter 1 is +5 mm, the force required to break the potassium silicate (assuming a circular shape) having a diameter of 5 mm is calculated.
19MPa x (0.0025) ² x π = 38kgf
Will be.

With reference to FIG. 3, this 38 kgf is worth 0.45 m as the drop height of the sinter 1. Therefore, a drop height of 0.45 m or more is required to destroy weak parts such as cracks 2 and fragile parts 3 in the sinter 1, and a drop height of 0.5 m or more is required in consideration of safety. It becomes.
Therefore, in the present embodiment, the drop height of the sinter 1 by the drop method is set to 0.5 m or more and 2.0 m or less.
In this drop method, in order to give an impact force to the sinter 1, the number of drops may be not limited to one, but may be multiple. When the number of drops is set to a plurality of times, partially weak parts such as cracks 2 and fragile parts 3 can be destroyed more than one drop.

When an impact force is applied to the sinter 1 by the rotary drum method, the inner diameter of the rotary drum into which the sinter 1 is placed is 1 m or more and 4 m or less, although not shown. Assuming that the inner diameter of the rotating drum is 1 m or more, the angle of repose of the sinter 1 is 45 ° or more, so it is considered that the sinter 1 is falling from a height of 0.5 m or more during rotation. Therefore, by setting the inner diameter of the rotary drum into which the sinter 1 is placed to 1 m or more, the impact force applied to the sinter 1 becomes 38 kgf or more, and partially weak parts such as cracks 2 and fragile parts 3 are removed. Can be destroyed. On the other hand, if the inner diameter of the rotating drum is made larger than 4 m, the drop height of the sinter 1 becomes larger than 2 m, so that the impact force applied to the sinter 1 cannot be suppressed to 100 kgf or less. Therefore, the inner diameter of the rotary drum in which the sinter 1 is placed is set to 1 m or more and 4 m or less.

Next, an impact force is applied to the sinter 1 after the primary crushing in step S103, and then the sinter 1 to which the impact force is applied is sieved in step S104.
Here, when an impact force is applied to the sinter 1 by the drop method, when the number of drops is one, the sinter 1 is sieved after the sinter 1 has fallen. As a result, partially weak portions such as cracks 2 and fragile portions 3 destroyed by the impact force are removed from the sinter 1, and the sinter 1 having improved overall strength can be produced.

Further, when an impact force is applied to the sinter 1 by the drop method, if the number of drops is a plurality of times, the sinter 1 is sieved between the drops, and further, after the final drop. The sinter 1 may be sieved, or the sinter 1 may be sieved after being dropped a plurality of times. In this way, when the sinter 1 is dropped a plurality of times, the sinter 1 is sieved between the drops, and the sinter 1 is further sieved after the final drop, or a plurality. By sieving the sinter 1 after dropping it once, partially weak parts such as cracks 2 and fragile parts 3 that were destroyed more than one drop can be removed from the sinter 1, and the overall strength can be improved. A more improved sinter 1 can be produced.
When an impact force is applied to the sinter 1 by the rotary drum method, the sinter 1 is sieved after the impact force is applied. Also by this, partially weak portions such as cracks 2 and fragile portions 3 destroyed by the impact force are removed from the sinter 1, and the sinter 1 having improved overall strength can be produced.
When the sinter 1 is sieved in step S104, the production of the sinter 1 is completed.

Although the embodiments of the present invention have been described above, the present invention is not limited to this, and various modifications and improvements can be made.
For example, the impact force may be applied to the sinter 1 by a method other than the drop method or the rotary drum method, for example, the vibration method.
Further, the impact force can be changed according to the strength required for the blast furnace raw material, and the drop height of the sinter 1 in the drop method is not limited to 0.5 m or more and 2.0 m or less.
Similarly, the inner diameter of the rotating drum in the rotating drum method is not limited to the case of 1 m or more and 4 m or less.

Further, before applying an impact force to the sinter after the primary crushing, the sinter is classified, the impact force is applied to the sinter only under the sieve, and the impact force is applied to the sinter. The sinter may be mixed with the sinter on the sieve and then the mixed sinter may be sieved. The number of times the impact force is applied to the sinter after the primary crushing may be one or more times. In the case of one time, the sinter is classified before the one impact force is applied, and only under the sieve is baked. The impact force is applied to the ore so that the impacted sinter under the sieve is mixed with the sinter on the sieve. When applying an impact force to the sinter multiple times, the sinter is classified before the impact force is applied at least once, and the impact force is applied to the sinter only under the sieve to apply the impact force. The sinter under the given sieve is to be mixed with the sinter on the sieve.

In order to verify the effect of the present invention, an impact force is applied to the sinter by the drop method and the sinter is sieved, and a test 1 and an impact force is applied to the sinter by the rotary drum method to sieve the sinter. Three types of tests were performed: Test 2 and Test 3 in which an impact force was applied only to the portion of the sinter that was easily pulverized to sieve the sinter.

(Test 1)
In Test 1, two tests, Example 1 and Example 2, were performed.
In Example 1, five sets of sinter having a particle size distribution of 10-30 mm and a particle ratio of 30-50 mm at a ratio of 50:50 were prepared, and each set of sinter was made into JIS M 8711 (drop height 2 m). ), A drop test (first time) was performed to measure the drop strength index (%). Then, each set of sinter was sieved, -10 mm of powder was removed, and a drop test (second time) was performed according to JIS M 8711 to measure the drop strength index (%). Then, each set of sinter was further sieved, -10 mm of powder was removed, and a drop test (third time) was performed according to JIS M 8711 to measure the drop strength index (%). Finally, each set of sinter was sieved, -10 mm of powder was removed, and a drop test (fourth time) was performed according to JIS M 8711 to measure the drop strength index (%).
FIG. 4 shows the relationship between the ratio of the particle size distribution (10-30 mm, 30-50 mm) in the drop test of Example 1 and the number of drop tests. Here, when calculating the ratio of the particle size distribution in Example 1 and Example 2 described below, the ratio of the mass passing through the sieve with the nominal opening according to JIS Z 8801-1 is obtained, and the ratio of the particle size distribution is calculated. I asked.

In Example 2, five sets of sinter having a particle size distribution of 10-30 mm and a particle ratio of 30-50 mm at a ratio of 50:50 were prepared, and each set of sinter was prepared as JIS M 8711 (drop height 2 m). ), A drop test (first time) was performed to measure the drop strength index (%). After that, each set of sinter was sieved to remove -10 mm powder and a part of 10-30 mm powder, and the ratio of particles having a particle size distribution of 10-30 mm and 30-50 mm was set to 50:50. A drop test (second time) was performed according to JIS M 8711, and the drop strength index (%) was measured. After that, each set of sinter is further sieved to remove -10 mm powder and a part of 10-30 mm powder, and the ratio of particles having a particle size distribution of 10-30 mm and 30-50 mm is 50:50. Then, a drop test (third time) was performed according to JIS M 8711, and the drop strength index (%) was measured. Finally, each set of sinter is sieved to remove -10 mm flour and part of the 10-30 mm flour, with a particle size distribution of 10-30 mm and 30-50 mm particles at a ratio of 50:50. , JIS M 8711 was used to perform a drop test (fourth time) to measure the drop strength index (%).
FIG. 5 shows the relationship between the ratio of the particle size distribution (10-30 mm, 30-50 mm) in the drop test of Example 2 and the number of drop tests.

FIG. 6 shows the relationship between the drop strength index increase value and the number of drop tests in the drop tests of Examples 1 and 2.
Here, the drop strength index increase value is a value (%) obtained by subtracting the drop strength index in the first drop test from the drop strength index in each drop test.
As a result, in the case of Example 1, the sinter of each set was sieved after the first drop test, -10 mm of powder was removed, and the drop strength index (%) when the second drop test was performed was obtained. It increased by about 0.2%, and in the case of Example 2, the sinter of each set was sieved after the first drop test to remove -10 mm powder and a part of 10-30 mm powder. It can be confirmed that the drop strength index (%) when the second drop test is performed has increased by about 2.2%. As a result, when an impact force is applied to the sinter 1 by the drop method, when the number of drops is one, the sinter 1 is sieved after the sinter 1 has fallen, thereby increasing the drop strength of the sinter. Was found to rise. Sintered ore powder with a particle size smaller than 10 mm and a part of the particle size of 10 mm-30 mm are considered to be equivalent to cracks and fragile parts.

Further, in the case of Example 1, the sinter of each set was sieved after the first drop test, -10 mm of powder was removed, and the drop strength index (%) when the second drop test was performed was about. It increased by 0.2%, and after the second drop test, each set of sinter was sieved to remove -10 mm of powder, and the drop strength index (%) when the third drop test was performed was about. It increased by 1.2%, and after the third drop test, each set of sinter was sieved to remove -10 mm of powder, and the drop strength index (%) when the fourth drop test was performed was about. It can be confirmed that it has increased by 2.0%. Further, in the case of Example 2, after the first drop test, each set of sinter is sieved to remove -10 mm powder and a part of 10-30 mm powder is removed, and the second drop test is performed. The drop strength index (%) increased by about 2.2% after the second drop test, and after the second drop test, each set of sinter was sieved to remove -10 mm powder and one of 10-30 mm powder. Excluding the part, the drop strength index (%) when the third drop test was performed increased by about 2.5%, and after the third drop test, each set of sinter was sieved and -10 mm powder was added. It can be confirmed that the drop strength index (%) in the fourth drop test is increased by about 4.5% by removing a part of the powder of 10-30 mm. As a result, when an impact force is applied to the sinter 1 by the drop method, when the number of drops is multiple (3 times), the sinter 1 is sieved between the drops, and finally. By sieving the sinter 1 after the fall of the sinter, the drop strength of the sinter 1 increases as compared with the case of one drop, and the drop strength of the sinter 1 increases as the number of drops increases. all right.

Further, comparing the case where the drop test of Example 1 was performed and the case where the drop test of Example 2 was performed, when the sinter 1 was sieved between drops, a powder of 10-30 mm was used. It was confirmed that in the drop test of Example 2 except for a part, the increase value of the drop strength of the sinter 1 was larger. The reason for this is that 10-30 mm particles are presumed to have more fragile points than 30-50 mm particles, and by removing some of the 10-30 mm particles that have more fragile points, the entire sinter This is because the average strength increases.

(Test 2)
In Test 2, three sets of reduced sinter were prepared, and one set of sinter was dropped according to JIS M 8711 (fall height 2 m), and the drop strength index (%) was measured. In addition, the remaining two sets of sinter were rotated according to JIS M 8712, and after the rotation, the sinter was sieved to remove -10 mm powder, and JIS M 8711 (dropped) per + 10 mm sinter. A drop test was performed according to (height 2 m), and the drop strength index (%) was measured.
As a result, as shown in FIG. 7, the drop strength index of one set of sinter (before treatment) that was not subjected to the rotation treatment was 93.1%, and the sinter for two sets that were sieved after the rotation treatment. The drop strength index of the ore (after treatment) was 97.6%, and it was confirmed that the drop strength index of the sintered ore sieved after the rotation treatment was significantly increased.

(Test 3)
Since it was found that fine particles may be the cause of pulverization, in Test 3, only the fine particles of the sinter were crushed to improve the strength. That is, in this test, the 5-50 mm sinter after the primary crushing is sieved (classified) with the sieves shown in Examples 4, 5 and 6 respectively, and the impact force is applied only under the sieve. The crushed material is mixed with the sinter on the sieve, and then the mixed sinter is sieved to remove powder of 5 mm or less, and the strength according to JIS M 8712, which shows the strength against both impact and abrasion. An evaluation test was conducted.

Table 1 shows, for Comparative Example 1, Example 3, Example 4, Example 5, and Example 6, a sieve for sieving into fine particles, and a sieve of 5 mm or more and each sieve or less when sieving. The lower ratio (ratio of crushing treatment), rotation treatment time (min), and rotation strength index (%) after rotation treatment are shown.
In Comparative Example 1, a strength evaluation test by JIS M 8712 was performed on a 5-50 mm sinter without any sieving or crushing.
In Example 3, for a 5-50 mm sinter, the whole was crushed by an impact force without sieving into fine particles, the crushed material was sieved, and the powder of 5 mm or less was removed, and the strength was evaluated by JIS M 8712. It was tested.

As a result, as shown in Table 1, as shown in Example 4-6, the sieve was sieved with a mesh of 8-30 mm (+ 5 mm), and only under the sieve was crushed so that the particles were not sieved into fine particles (implementation). It was found that an improvement in the rotational strength index can be obtained as compared with Example 3). The reason for this is considered to be that the normal portion of the sinter is also cracked by crushing the entire amount as in Comparative Example 1 and Example 3. Therefore, it is possible to obtain a high-strength sinter with high efficiency by applying an impact force only to the portion that is easily pulverized.
Further, crushing only under the sieve also has an effect of lowering the crushing cost as compared with crushing the entire amount as in Comparative Example 1 and Example 3.

1 Sintered ore 2 Crack 3 Vulnerable part

Claims (7)

A method for producing sintered ore to be introduced into a blast furnace.
A method for producing a sinter, which comprises applying an impact force of 38 kgf or more and 100 kgf or less to the sinter after the primary crushing, and then sieving the sinter given the impact force. The method for producing a sinter according to claim 1, wherein the impact force is applied to the sinter by a drop method or a rotary drum method. The method for producing a sinter according to claim 2, wherein the drop height of the sinter in the drop method is 0.5 m or more and 2.0 m or less. The method for producing a sinter according to claim 2 or 3, wherein the dropping method is for dropping the sinter a plurality of times. The impact force is applied once or a plurality of times, and the sinter is classified before the impact force is applied at least once, and the impact force is applied to the sinter only under the sieve. The method for producing a sinter according to any one of claims 1 to 4, wherein the sinter under the given sieve is mixed with the sinter on the sieve. The method for producing a sinter according to claim 2, wherein the rotary drum method is a method in which the sinter is placed in a rotary drum and subjected to a rotation treatment. The method for producing a sinter according to claim 6, wherein the inner diameter of the rotary drum is 1 m or more and 4 m or less.

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