Method for manufacturing sintered ore

Abstract

To reduce carbon dioxide emissions, PKS coal is mixed into the sintering raw material, and to increase the total Fe content, concentrate ore is mixed into the sintering raw material, and yet the granulation properties of the sintering raw material can be improved. A method for producing sintered ore, comprising: a raw material blending step (step S101) in which iron raw material and solid carbon material including a first carbon material and a second carbon material are blended and granulated to produce a sintering raw material; a raw material layer forming step (step S102) in which the sintering raw material is supplied onto a pallet of a sintering machine to form a raw material layer; and a sintering step (step S103) in which the upper surface of the raw material layer is ignited and fired to produce sintered ore, wherein in the raw material blending step (step S101), palm kernel shell charcoal is blended as the first carbon material, and carbon material derived from fossil fuels is blended as the second carbon material, and the arithmetic mean particle size of the palm kernel shell charcoal is smaller than the arithmetic mean particle size of the second carbon material.

Description

Technical Field

[0001] The present invention relates to a method for producing sintered ore.

Background Art

[0002] The sintering process for producing sintered ore, which is one of the iron ore raw materials for blast furnaces, is a process in which ignition occurs on the upper layer of the sintering raw materials charged into a sintering machine, and air is sucked from the lower layer of the sintering raw materials to cause the flame to propagate from the upper layer to the lower layer of the sintering raw materials to bake the entire layer of the sintering raw materials. The sintering raw materials are blended with an iron raw material, a flux for component adjustment, and a solid carbonaceous material. Examples of the iron raw material include powdered iron ores and return ore.

[0003] In the sintering process, a large amount of anthracite and pulverized coke derived from fossil fuels (hereinafter sometimes referred to as coal) are used as the solid carbonaceous material, and a part of these is replaced with a carbon-neutral material (sometimes referred to as biomass charcoal). This is to meet the requirement for reducing carbon dioxide emissions in the sintering process. Among the carbon-neutral materials, palm coconut shell charcoal (hereinafter referred to as PKS charcoal) is relatively widely distributed and is used as the carbonaceous material in the sintering process. In the sintering process, since a large amount of coal is used, due to the problem of the supply amount, the total amount of coal cannot be replaced with PKS charcoal, and only a part of the coal is replaced with PKS charcoal.

[0004] Patent Document 1 and Patent Document 2 describe a method for producing sintered ore in which a part of the carbonaceous material derived from fossil fuel is replaced with coarse-grained abura coconut shell charcoal, thereby improving the combustion rate of the sintering raw materials in the sintering process. By doing so, it is said that the productivity of the sintered ore can be improved. Note that abura coconut shell charcoal is the same as palm coconut shell charcoal, and hereinafter, they are collectively referred to as PKS charcoal.

[0005] On the other hand, there is the challenge of declining iron ore quality. To counteract the decrease in iron grade in iron ore, ore dressing is sometimes performed. Ore dressing means crushing the mined iron ore and separating it into iron ore with a high iron grade from iron ore with a low iron grade. The iron ore with a high iron grade that is separated in this way (hereinafter referred to as concentrate ore) is shipped. Concentrate ore has a low gangue component in the ore. Therefore, it is added to the sintering raw material in order to dilute the gangue component in the sintered ore produced in the sintering process. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Patent No. 6102484 [Patent Document 2] Patent No. 5786795 [Overview of the project] [Problems that the invention aims to solve]

[0007] The deterioration of iron ore quality has led to its pulverization year by year. Because the particle size of iron ore differs between the present time and before, this difference in particle size is causing differences in the granulation properties of the sintering raw material. Patent documents 1 and 2 disclose a method for replacing part of the fossil fuel-derived carbon material with PKS coal, but the particle size of the iron ore to be blended into the sintering raw material is not specified at all. Furthermore, as mentioned above, the pulverization of iron ore has progressed further since the invention of the methods described in Patent documents 1 and 2. Therefore, if, at present, part of the fossil fuel-derived carbon material is replaced with PKS coal based on the sintering ore manufacturing method described in Patent documents 1 and 2, the pulverization of iron ore may cause a deterioration in the granulation properties of the sintering raw material.

[0008] Furthermore, if some of the iron raw materials used in the sintering raw material are replaced with concentrate ore, the poor wettability of concentrate ore can also worsen the granulation properties of the sintering raw material. When the granulation properties of the sintering raw material worsen, operating conditions deteriorate when firing the sintering raw material in the sintering machine, such as misfires and a decrease in combustion rate due to poor permeability. As a result, there is a problem of reduced productivity of sintered ore.

[0009] The present invention was made to solve the above problems, and aims to provide a method for producing sintered ore that can improve the granulation properties of the sintered raw material, even when PKS carbon is mixed into the sintered raw material to reduce carbon dioxide emissions, and concentrate ore is mixed into the sintered raw material to increase the total Fe content. [Means for solving the problem]

[0010] The means to solve the above problems are as follows: [1] A method for producing sintered ore, comprising: a raw material blending step of blending and granulating an iron raw material containing concentrate ore and powdered iron ore with a solid carbon material containing a first carbon material and a second carbon material having a higher combustion start temperature than the first carbon material to produce a sintering raw material; a raw material layer forming step of supplying the sintering raw material onto a pallet of a sintering machine to form a raw material layer; and a sintering step of igniting the upper surface of the raw material layer to fire the sintering raw material to produce sintered ore, wherein in the raw material blending step, palm kernel shell charcoal is blended as the first carbon material, and fossil fuel-derived charcoal is blended as the second carbon material, and the arithmetic mean particle size of the palm kernel shell charcoal is smaller than the arithmetic mean particle size of the second carbon material. [2] The method for producing sintered ore according to [1], wherein the raw material blending step involves blending palm kernel shell charcoal having an arithmetic mean particle size of 1.10 mm or less. [3] The method for producing sintered ore according to [1] or [2], wherein in the raw material blending step, the concentrate ore is blended with the iron raw material such that the blending ratio of the concentrate ore to the iron raw material is 5.0 to 30.0% by mass. [4] The method for producing sintered ore according to any one of [1] to [3], wherein in the raw material blending step, the palm kernel shell charcoal is blended into the solid carbon material such that the blending ratio of the palm kernel shell charcoal to the solid carbon material is 10.0 to 50.0% by mass. [Effects of the Invention]

[0011] According to the present invention, even when PKS carbon is mixed into the sintering raw material to reduce carbon dioxide emissions, and concentrate ore is mixed into the sintering raw material to increase the total Fe content, the granulation properties of the sintering raw material can be improved. [Brief explanation of the drawing]

[0012] [Figure 1] This is a diagram illustrating the manufacturing method of the sintered ore according to this embodiment. [Figure 2] This figure shows an example of a sintering ore manufacturing facility to which the sintering ore manufacturing method of this embodiment can be applied. [Figure 3] This diagram illustrates the manufacturing process of PKS charcoal and the method for adjusting its particle size. [Modes for carrying out the invention]

[0013] Hereinafter, embodiments of the present invention (hereinafter referred to as "this embodiment") will be described with reference to the drawings. Figure 1 is a diagram illustrating the method for manufacturing sintered ore according to this embodiment. In the example shown in Figure 1, first, a sintering raw material is produced by mixing a plurality of raw materials in predetermined proportions (step S101, raw material mixing step). Figure 2 is a diagram showing an example of a sintered ore manufacturing facility to which the method for manufacturing sintered ore according to this embodiment can be applied. As shown in Figure 2, a plurality of hoppers 1 are provided in the sintered ore manufacturing facility. Each raw material is stored in one of these hoppers 1.

[0014] The raw materials for sintering include iron raw materials, auxiliary raw materials, and solid carbon materials (hereinafter simply referred to as carbon materials). Examples of iron raw materials include powdered iron ore, return ore, and concentrate ore. Concentrate ore refers to high-iron grade iron ore separated from mined iron ore by ore dressing. Concentrate ore has less gangue component compared to iron ore before ore dressing. Therefore, in this embodiment, it is blended into the iron raw material to dilute the gangue component in the sintered ore produced using degraded iron ore and increase the total Fe content. The blending ratio of concentrate ore in the iron raw material is preferably 5.0 to 30.0% by mass. This is because if the blending ratio of concentrate ore is less than 5.0% by mass, the gangue component cannot be diluted. If the blending ratio of concentrate ore exceeds 30.0% by mass, it becomes difficult to form granulated particles, as described later. Furthermore, concentrate ore has the characteristic of not easily retaining moisture on its surface, and therefore is less prone to aggregation. To facilitate the aggregation of concentrate ore, PKS coal with a smaller particle size than powdered coke is added to the sintering raw material, as will be described later. In the following explanation, "mass%" will simply be written as "%".

[0015] Examples of auxiliary raw materials include limestone, dolomite, and quicklime.

[0016] Examples of carbon materials include pulverized coke and anthracite, which are carbon materials derived from fossil fuels, and palm coconut shell charcoal (hereinafter referred to as PKS charcoal), which is derived from biomass. In this embodiment, in order to reduce the amount of carbon dioxide emissions generated when producing sintered ore, PKS charcoal is blended with carbon materials derived from fossil fuels. The arithmetic average particle size of PKS charcoal (hereinafter simply referred to as the average particle size) is preferably smaller than the average particle size of pulverized coke. This is for improving granulation properties. Also, the surface of PKS charcoal is smooth and has few open pores, and it is less likely to retain moisture compared to pulverized coke. Therefore, by pulverizing PKS charcoal to reduce its particle size, the specific surface area is increased so that moisture can be retained on the surface of PKS charcoal. Specifically, since the average particle size of pulverized coke is about 1.20 mm, it is preferable to pulverize PKS charcoal so that its average particle size is 1.10 mm or less, which is smaller than the average particle size of pulverized coke. If the average particle size of PKS charcoal exceeds 1.10 mm, the mass ratio of the iron raw material in the granulated particles becomes excessively small, and moisture cannot be retained on the surface of PKS charcoal, making it difficult to form granulated particles.

[0017] Furthermore, the blending ratio of PKS charcoal in the solid carbon material is preferably about 10.0 to 50.0%. This is because, as will be described later, when the blending ratio of PKS charcoal is less than 10.0%, it becomes difficult to agglomerate the concentrate ore when the iron raw material contains the concentrate ore. When the blending ratio of PKS charcoal exceeds 50.0%, the high combustibility of PKS charcoal may cause the yield of sintered ore to decrease excessively. Note that PKS charcoal among the above-described carbon materials corresponds to the first carbon material of this embodiment, and pulverized coke and anthracite correspond to the second carbon material of this embodiment. PKS charcoal will be described later.

[0018] [[ID=z]] In the example shown in FIG. 2, each raw material is supplied from the hopper 1 storing various raw materials onto a conveyor not shown at a predetermined ratio, and is conveyed to the drum mixer 2 by the conveyor.

[0019] In the drum mixer 2, each raw material is mixed, water is added to the mixture of each raw material for humidity adjustment, and a sintering raw material containing granulated particles (sometimes referred to as pseudo-particles) granulated to a predetermined average particle size is produced. Then, the sintering raw material is conveyed to the surge hopper 3 by a conveyor and temporarily stored. The process of manufacturing the sintering raw material as described above corresponds to the raw material blending process of the present embodiment.

[0020] Return to the description of FIG. 1. Following the raw material blending process of step S\(_{101}\), proceed to the raw material layer forming process of step S\(_{102}\). In the raw material layer forming process, the sintering raw material is charged onto the pallet 10 of the sintering machine 9, and a raw material layer 7 is formed on the pallet 10. That is, the sintering raw material stored in the surge hopper 3 shown in FIG. 2 is cut out by the drum feeder 4 and charged onto the bedding ore layer 6 through the chute 5. Thus, the raw material layer 7 is formed.

[0021] In the example shown in FIG. 2, a bedding ore hopper 8 is provided upstream of the surge hopper 3 in the conveying direction of the sintering raw material in the sintering machine 9. The bedding ore is stored in the bedding ore hopper 8. The bedding ore is cut out from the drum feeder of the bedding ore hopper 8 and charged onto the pallet 10 of the sintering machine 9 through the chute to form the bedding ore layer 6.

[0022] A cutoff gate 11 is installed downstream of the surge hopper 3 in the conveying direction of the sintering raw material to level the surface of the raw material layer 7 on the pallet 10 and make the thickness of the raw material layer 7 substantially uniform. By passing through the cutoff gate 11, a raw material layer 7 with a predetermined thickness is formed. Thus, the process of charging onto the pallet 10 to form a raw material layer 7 with a predetermined thickness corresponds to the raw material layer forming process of the present embodiment.

[0023] Returning to the explanation of Figure 1, the process proceeds from the raw material layer formation step in step S102 to the sintering step in step S103. In the sintering step, the raw material layer 7 formed on the pallet 10 of the sintering machine 9 is ignited, and the sintering material is sintered. As shown in Figure 2, an ignition furnace 12 is provided downstream of the cutoff gate 11 in the transport direction. The ignition furnace 12 ignites the carbon material present on the surface (upper surface) of the raw material layer 7. In addition, multiple window boxes 13 are arranged below the pallet 10 in the vertical direction of the sintering machine 9. A sintering fan 15 is connected to each window box 13 via an exhaust pipe 14. The sintering fan 15 draws in air from inside the window boxes 13. This causes air to circulate from top to bottom in the thickness direction of the raw material layer 7. This also causes the combustion of the carbon material in the sintering material to proceed from top to bottom of the raw material layer 7. The sintering raw materials are heated by the combustion heat of the carbon material, causing at least a portion of the iron raw materials to melt and bond together, and the sintering of the raw materials progresses from the top to the bottom of the raw material layer 7. In this way, a sintered raw material layer (sometimes called a sintered cake) is formed on the pallet 10 of the sintering machine 9. This process of sintering the raw materials corresponds to the sintering process described above.

[0024] In the example shown in Figure 2, a dust collector 16 is provided upstream of the sintering fan 15 in the direction of airflow to collect dust from the air and fine particles from the sintering material. A chimney 17 is provided downstream of the sintering fan 15 in the direction of airflow. The air drawn in by the sintering fan 15 is discharged to the outside through the chimney 17.

[0025] The sintered cake formed on the pallet 10 of the sintering machine 9 is discharged to the outside of the sintering machine 9 from the ore discharge section on the downstream side of the sintering machine 9 in the transport direction. Subsequently, the sintered cake is crushed and separated by the crusher 18, and sintered ore of predetermined particle sizes is recovered as finished sintered ore.

[0026] (PKS charcoal) Here, we will explain PKS charcoal. PKS charcoal is a charcoal material produced by dry distillation of palm kernel shells (hereinafter referred to as PKS). PKS, which is the raw material for PKS charcoal, absorbs carbon dioxide during its growth. Therefore, when PKS charcoal, which is produced by dry distillation of PKS, is burned, it can be considered that there are no carbon dioxide emissions into the environment from the perspective of carbon neutrality. Thus, from the perspective of carbon neutrality, if biomass charcoal such as PKS charcoal is blended into the sintering raw material, carbon dioxide emissions can be reduced accordingly.

[0027] One of the characteristics of PKS is that, compared to powdered coke and anthracite, it has a higher proportion of volatile matter and a lower combustion start temperature. The volatile matter of PKS is 70-80%. By dry distillation of PKS, it becomes PKS coal, and the volatile matter is reduced to about 3-5%. The combustion start temperature of PKS coal is 420°C, which is lower than the combustion start temperature of powdered coke, which is 624°C. Also, as mentioned above, the surface of PKS coal is smooth and has few open pores, making it difficult to retain moisture on the surface. Therefore, in this embodiment, the specific surface area is increased by crushing the PKS coal, making it possible to retain moisture on its surface. By doing so, when concentrate ore and PKS coal are blended into the sintering raw material, the concentrate ore is made more likely to aggregate, improving the granulation properties of the sintering raw material.

[0028] (Manufacturing method for PKS charcoal and method for adjusting particle size) Figure 3 is a diagram illustrating the production of PKS coal and the method for adjusting particle size. In Figure 3, for example, first, PKS is carbonized at 1000°C for 1 hour (step S201). The carbonization method of PKS is not limited, and PKS may be carbonized using a batch-type carbonization furnace (not shown). Alternatively, PKS may be carbonized using a kiln-type continuous carbonization furnace instead of a batch-type carbonization furnace. Furthermore, carbonization of PKS reduces the volatile content of the PKS coal to less than 5%. This is to suppress problems such as smoke generation during exhaust gas treatment in the sintering process. Although uncarbonized PKS is difficult to crush, carbonization improves the crushability after carbonization compared to before carbonization. To ensure the crushability of PKS coal, the hard globe crushability index (HGI) of PKS coal is preferably 25 or higher, and more preferably 30 or higher, the same as the HGI of powdered coke. HGI can be measured using the method described in JIS M 8801:2008. Furthermore, HGI can be changed by altering the carbonization time.

[0029] Following step S201, the PKS coal is crushed to make its particle size smaller than that of fossil fuel-derived carbon material (step S202). This is done to increase the specific surface area of ​​the PKS coal, thereby making it easier to retain moisture on its surface. This also improves the granulation properties of the sintering raw material by making it easier for the concentrate ore to aggregate when the concentrate ore and PKS coal are blended together. The method of crushing the PKS coal is not limited, but for example, the PKS coal may be crushed using a jaw crusher or a disc mill. As for fossil fuel-derived carbon material, powdered coke can be the main example.

[0030] Next, the crushed PKS coal is sieved using a sieve with the same mesh size as the average particle size of the coke powder to separate it into PKS coal with a particle size greater than or equal to the average particle size of the coke powder and PKS coal with a particle size less than or equal to the average particle size of the coke powder (step S203). Since the average particle size of the coke powder is about 1.20 mm, it is preferable to use a sieve with a mesh size of about 1.10 mm to sieve the crushed PKS coal. For PKS coal with a particle size greater than or equal to the average particle size of the coke powder (No in step S203), the process is repeated in step S202 to crush the PKS coal again. For PKS coal with a particle size less than the average particle size of the coke powder (Yes in step S203), the PKS coal is recovered as a charcoal material to be blended into the sintering raw material (step S204).

[0031] (Effects / Actions) In this embodiment, the PKS coal is crushed to reduce its particle size, which increases its specific surface area and makes it easier to retain moisture on its surface. Therefore, even if the concentrate ore does not retain moisture well and does not agglomerate easily, the moisture retained by the PKS coal can agglomerate the concentrate ore, improving the granulation properties of the sintering raw material. In addition, because the PKS coal is crushed and its particle size is reduced, it burns more easily compared to before crushing. Therefore, it is possible to suppress the remaining unburned carbon material on the pallet 10 when firing the sintering raw material. In other words, the combustibility of the sintering raw material on the pallet 10 is improved, and the overall production yield of the sintered ore can be improved. Furthermore, in this embodiment, since a portion of the carbon material is replaced with PKS coal, the amount of carbon dioxide emitted in the sintering process can be reduced. [Examples]

[0032] Example 1, which verified the effects of this embodiment, will now be described. First, PKS was divided into small portions in small dishes and placed together in a batch-type carbonization furnace (hereinafter referred to as the carbonization furnace). In the carbonization furnace, PKS was carbonized at 1000°C for 6 hours under a nitrogen atmosphere to produce PKS coal. Next, the PKS coal was crushed using a jaw crusher and a disc mill to produce three types of PKS coal A, B, and C with different average particle sizes. Powdered coke was also prepared as a fossil fuel-derived carbon material. The particle size distribution of powdered coke and each of the PKS coals A, B, and C is summarized in Table 1. In the following description, "mass %" will simply be written as "%".

[0033] [Table 1]

[0034] Furthermore, the volume of open pores per unit mass of PKS coals A, B, and C, and the volume of open pores per unit mass of powdered coke were measured using the mercury porosimeter method. The volume of open pores for each of PKS coals A, B, and C was 0.11 cm³. 3 The volume of open pores in powdered coke per unit mass is 0.67 cm³ / g. 3 The value was / g. Thus, the volume of open pores per unit mass of each PKS coal A, B, and C is less than the volume of open pores per unit mass of powdered coke.

[0035] Iron raw materials, a solvent for adjusting the composition, and carbon materials were mixed in predetermined proportions, and granulated particles were formed by adding small amounts of water to the mixture. Examples of iron raw materials include powdered iron ore, return ore, and concentrate ore. In this Example 1, a portion of the powdered iron ore was replaced with concentrate ore. Examples of a solvent for adjusting the composition include limestone. Examples of carbon materials include PKS coal A, B, and C, and powdered coke. In this Example 1, one of each of PKS coal A, B, and C and powdered coke were used as the carbon material. In other words, a portion of the powdered coke was replaced with one of PKS coal A, B, or C. The proportions (mass%) of each raw material are summarized in Table 2. As shown in Table 2, the proportion of concentrate ore in the iron raw materials excluding return ore is 5.0%, 20.0%, or 30.0%. The proportion of PKS charcoal in the charcoal material is 10.0%, 25.0%, or 50.0%.

[0036] [Table 2]

[0037] Table 3 summarizes the brand names and particle size distributions of the iron ore powder used in this embodiment, as well as the particle size distribution of the concentrate ore.

[0038] [Table 3]

[0039] Table 4 summarizes the particle size distribution of the granulated particles after drying. The particle size, or harmonic mean diameter, of the granulated particles was calculated by sieving after drying.

[0040] [Table 4]

[0041] (evaluation) Experimental Examples 1, 2, and Comparative Example 1 all involve a concentration ore content of 5.0% in the carbon material, and the types of PKS coal, i.e., the particle sizes, differ from one another. In Experimental Examples 1, 2, and Comparative Example 1, as shown in Table 4, it was found that the harmonic mean diameter of the granulated particles decreased as the particle size of the PKS coal increased. The harmonic mean diameter of the granulated particles in Comparative Example 1 was less than 0.60 mm, and fine particles penetrated the voids through which air could pass when packed. As a result, the voids were blocked, which is thought to be causing a deterioration in the permeability of the raw material layer on the sintering machine pallet.

[0042] Experimental Examples 2-4 show cases where the proportion of concentrate ore was increased to 5.0%, 20.0%, and 30.0%, while the type and proportion of PKS coal were kept constant. In Experimental Examples 2-4, the harmonic mean diameter decreased as the proportion of concentrate ore increased. In Experimental Example 4, although the harmonic mean diameter is 0.60 mm or more, the particle size of the granulated particles is the smallest among Experimental Examples 2-4 and is close to the threshold (harmonic mean diameter of 0.60 mm). Therefore, it is considered preferable that the proportion of concentrate ore relative to the powdered iron ore be 30.0% or less.

[0043] Comparative Example 2 is an example in which granulated particles were formed in the same manner as in Experimental Example 4, except that the particle size of the PKS charcoal was increased. As shown in Table 4, the harmonic mean diameter of the granulated particles in Comparative Example 2 was 0.57 mm, which is smaller than the harmonic mean diameter of the granulated particles in Experimental Example 4. This is thought to be due to the increase in the particle size of the PKS charcoal. Also, since the harmonic mean diameter in Comparative Example 2 is less than 0.60 mm, it is thought that, similar to Comparative Example 1, deterioration in the permeability of the raw material layer on the sintering machine pallet occurred.

[0044] Experimental Example 5 is an example in which granulated particles were formed in the same manner as in Experimental Example 3, except that the PKS coal blending ratio was 25.0%. Experimental Example 6 is an example in which granulated particles were formed in the same manner as in Experimental Example 3, except that the PKS coal blending ratio was 50.0%. In Experimental Examples 3, 5, and 6, as shown in Table 4, the harmonic mean diameter of the granulated particles increased with increasing PKS coal blending ratio. From these results, it can be concluded that granulation performance improves with increasing PKS coal blending ratio.

[0045] Comparative Example 3 is an example in which granulated particles were formed in the same manner as in Experimental Example 6, except that the particle size of the PKS charcoal was increased. As shown in Table 4, the harmonic mean diameter of the granulated particles in Comparative Example 3 was 0.56 mm, which is smaller than the harmonic mean diameter of the granulated particles in Experimental Example 6. This is thought to be due to the increase in the particle size of the PKS charcoal. Also, in Comparative Example 3, since the harmonic mean diameter is less than 0.60 mm, it is thought that, similar to Comparative Example 1, deterioration in the permeability of the raw material layer on the sintering machine pallet occurred. [Examples]

[0046] (Sintered ore production test) Based on the results of the granulation test in Example 1, a sintered ore production test was conducted as Example 2. Specifically, the granulated particles from Experimental Examples 1-6 and Comparative Examples 1-3 were charged into a batch-type sintering pot test apparatus (hereinafter simply referred to as "apparatus") and fired. In this way, sintered ores for Experimental Examples 1-6 and Comparative Examples 1-3 were produced. The apparatus described above has a raw material charging section with a diameter of 300 mm and a height of 400 mm, and is equipped with an ignition furnace and exhaust gas equipment such as a wind box and blower. Therefore, it is possible to conduct sintered ore production tests that simulate an actual sintering machine.

[0047] After firing, the sintered ore was removed from the apparatus, and the yield and production rate of the sintered ore were measured. Here, yield refers to the mass percentage of sintered ore with a particle size of 5.00 mm or larger relative to the total amount of sintered ore, after dropping the sintered ore from a height of 2 m onto the mounting surface four times to crush it. Production rate is the value obtained by dividing the amount of sintered ore with a particle size of 5.00 mm or larger by the time required to produce the sintered ore and the area of ​​the raw material layer in the apparatus. A higher value indicates better productivity. The yield and production rate of the sintered ore for Experimental Examples 1-6 and Comparative Examples 1-3 are summarized in Table 5.

[0048] [Table 5]

[0049] Comparing Experimental Examples 1 and 2 with Comparative Example 1, the yield and production rate of Experimental Example 1 were higher than those of Experimental Example 2, and the yield and production rate of Experimental Example 2 were higher than those of Comparative Example 1. This is thought to be because the particle size of PKS coal gradually increased in the order of Experimental Examples 1, 2, and Comparative Example 1, and consequently the particle size of the granulated particles decreased, leading to a deterioration in permeability in the raw material layer during the production of sintered ore in this order. In other words, it is thought that in Experimental Examples 1 and 2, the improved permeability compared to Comparative Example 1 allowed for more uniform firing and improved overall yield. Furthermore, since PKS coal has better combustibility than powdered coke, it is thought that the proportion of unburned carbon decreased, resulting in improved yield. Unburned carbon refers to Free-C contained in sintered ore with a particle size of less than 5.00 mm after yield measurement. The unburned carbon content in the sintered ore of Experimental Example 1 was 0.13%, in the sintered ore of Experimental Example 2 it was 0.14%, and in the sintered ore of Comparative Example 1 it was 0.21%.

[0050] We will examine the reasons for the improved production rate. This is because reducing the particle size of PKS coal increases its specific surface area. This is thought to be due to an improvement in the combustion rate of PKS coal. Furthermore, even under conditions where the proportion of concentrate ore was increased compared to Experimental Examples 1 and 2, i.e., Experimental Examples 3 and 4, and Comparative Example 2, it was found that reducing the particle size of PKS coal could improve the yield and production rate of sintered ore, as shown in Table 5.

[0051] Comparing Experimental Examples 2, 3, and 4, it was found that yield and production rates decreased with increasing concentration ore content. As shown in Table 4, this is likely because the harmonic mean diameter of the granulated particles gradually decreased in the order of Experimental Example 2, 3, and 4, leading to increased uneven firing during the calcination of the raw material layer. In other words, it is expected that the permeability of the raw material layer decreased in the order of Experimental Example 2, 3, and 4, making uniform calcination impossible. Based on these results, it is considered preferable that the concentration ore content be 30.0% or less.

[0052] Furthermore, comparing Experimental Example 4 with Comparative Example 2, Comparative Example 2 showed lower yield and production rates than Experimental Example 4. This is thought to be because the harmonic mean diameter of the granulated particles in Comparative Example 2 was smaller than that of Experimental Example 4, resulting in reduced permeability of the raw material layer.

[0053] Comparing Experimental Examples 3, 5, and 6, the production rate improved as the proportion of PKS coal increased, but the yield decreased. We will examine the reason for the increased production rate. PKS coal has higher combustibility than powdered coke. Therefore, it is thought that increasing the proportion of PKS coal increases the firing rate in the raw material layer. We will also examine the reason for the decreased yield. As mentioned above, PKS coal has higher combustibility than powdered coke. This means that the combustion rate of PKS coal is high. On the other hand, the high combustion rate may lead to increased incomplete combustion of PKS coal, potentially preventing the complete combustion of the PKS coal. This is thought to result in insufficient heat for the sintered ore, leading to a decrease in yield. Furthermore, based on these results, it is considered preferable that the proportion of PKS coal in the coal material be 50.0% or less.

[0054] In Comparative Example 3, the raw material layer failed to fire during firing, preventing the firing process from being completed. As a result, sintered ore could not be produced. This is likely because the harmonic mean diameter of the granulated particles in Comparative Example 3 was the smallest among Experimental Examples 1-6 and Comparative Examples 1-3, as shown in Table 4, resulting in poor permeability. [Explanation of symbols]

[0055] 1 Hopper 2 Drum Mixer 3. Surge Hopper 4 Drum Feeder 5 shots 6. Subgrade ore layer 7 Raw material layer 8. Floor-filling ore hopper 9. Sintering machine 10 pallets 11 Cut-off gate 12 Ignition furnace 13 Window Box 14 Exhaust pipe 15 Sintering Fan 16 Dust collector 17 Chimney 18 Crusher S1 Raw Material Blending Engineering S2 Raw Material Layer Formation Engineering S3 Sintering Project

Claims

1. A method for producing sintered ore, comprising: a raw material blending step of blending and granulating an iron raw material containing concentrate ore having a particle size of less than 2.80 mm and powdered iron ore, and a solid carbon material containing a first carbon material and a second carbon material having a higher combustion start temperature than the first carbon material; a raw material layer forming step of supplying the sintered raw material onto a pallet of a sintering machine to form a raw material layer; and a sintering step of igniting the upper surface of the raw material layer to fire the sintered raw material and produce sintered ore, the method being used In the aforementioned raw material blending process, palm kernel shell charcoal is blended as the first charcoal material. The second carbon material is a carbon material derived from fossil fuels, A method for producing sintered ore, wherein the arithmetic mean particle size of the palm kernel shell char is smaller than the arithmetic mean particle size of the second char material.

2. The method for producing sintered ore according to claim 1, wherein the raw material blending step involves blending palm kernel shell charcoal having an arithmetic mean particle size of 1.10 mm or less.

3. The method for producing sintered ore according to claim 1 or 2, wherein in the raw material blending step, the concentrate ore is blended with the iron raw material such that the blending ratio of the concentrate ore to the iron raw material is 5.0 to 30.0% by mass.

4. The method for producing sintered ore according to claim 1 or 2, wherein in the raw material blending step, the palm kernel shell charcoal is blended into the solid carbon material such that the blending ratio of the palm kernel shell charcoal to the solid carbon material is 10.0 to 50.0% by mass.

5. The method for producing sintered ore according to claim 3, wherein in the raw material blending step, the palm kernel shell charcoal is blended into the solid carbon material such that the blending ratio of the palm kernel shell charcoal to the solid carbon material is 10.0 to 50.0% by mass.

6. The concentrate ore contains 1.7% by mass of particles with a particle size of 0.06 mm or less, 11.2% by mass of particles with a particle size of 0.06 to 0.13 mm, 47.3% by mass of particles with a particle size of 0.13 to 0.25 mm, 32.3% by mass of particles with a particle size of 0.25 to 0.50 mm, 6.5% by mass of particles with a particle size of 0.50 to 1.00 mm, and 0.9% by mass of particles with a particle size of 1.00 to 2.80 mm. The aforementioned iron ore powder consists of iron ore powder from Australia and iron ore powder from Brazil. The aforementioned Australian iron ore powder contains 3.5% by mass of particles with a particle size of 0.06 mm or less, 2.2% by mass of particles with a particle size of 0.06 to 0.13 mm, 4.3% by mass of particles with a particle size of 0.13 to 0.25 mm, 8.6% by mass of particles with a particle size of 0.25 to 0.50 mm, 12.7% by mass of particles with a particle size of 0.50 to 1.00 mm, 31.1% by mass of particles with a particle size of 1.00 to 2.80 mm, 16.8% by mass of particles with a particle size of 2.80 to 4.75 mm, and 20.7% by mass of particles with a particle size of 4.75 to 8.00 mm. The method for producing sintered ore according to claim 1, wherein the Brazilian powdered iron ore contains 9.9% by mass of particles with a particle size of 0.06 mm or less, 10.2% by mass of particles with a particle size of 0.06 to 0.13 mm, 11.3% by mass of particles with a particle size of 0.13 to 0.25 mm, 11.4% by mass of particles with a particle size of 0.25 to 0.50 mm, 10.5% by mass of particles with a particle size of 0.50 to 1.00 mm, 17.8% by mass of particles with a particle size of 1.00 to 2.80 mm, 16.0% by mass of particles with a particle size of 2.80 to 4.75 mm, and 12.8% by mass of particles with a particle size of 4.75 to 8.00 mm.

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