Method for producing sintered ore

Abstract

The present invention provides a method for producing a sintered ore, with which it is possible to improve granulation properties of a sintering starting material even in cases where PKS charcoal is mixed with the sintering starting material in order to reduce the discharge amount of carbon dioxide, and ore concentrate is mixed with the sintering starting material in order to increase the total Fe amount.　The method for producing a sintered ore comprises: a starting material blending step (step S101) for blending and granulating an iron starting material and a solid carbonaceous material that contains a first carbonaceous material and a second carbonaceous material so as to produce a sintering starting material; a starting material layer formation step (step S102) for supplying the sintering starting material onto a pallet of a sintering machine so as to form a starting material layer; and a sintering step (step S103) for igniting and firing the upper surface of the starting material layer so as to produce a sintered ore. In the starting material blending step (step S101), palm shell charcoal is blended as the first carbonaceous material, and a carbonaceous material derived from a fossil fuel is blended as the second carbonaceous material. The arithmetic average particle diameter of the palm shell charcoal is smaller than the arithmetic average particle diameter of the second carbonaceous material.

Description

Method for manufacturing sintered ore

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

[0002] The sintering process for manufacturing sintered ore, which is one of the iron ore raw materials for blast furnaces, is a process in which ignition occurs in 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 propagate the flame from the upper layer to the lower layer of the sintering raw materials to sinter the entire layer of the sintering raw materials. The sintering raw materials are blended with iron raw materials, flux for component adjustment, and solid carbonaceous materials. Examples of iron raw materials include powdered iron ores and return ore.

[0003] In the sintering process, a large amount of anthracite or pulverized coke derived from fossil fuels (hereinafter sometimes referred to as coal) is used as the solid carbonaceous material, and a part of these is replaced with carbon neutral materials (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 circulated and is used as a 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 manufacturing sintered ore in which the combustion rate of the sintering raw materials in the sintering process is improved by replacing a part of the carbonaceous material derived from fossil fuels with coarse-grained abura coconut shell charcoal. By doing so, it is said that the productivity of sintered ore can be improved. 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.

[0006] Patent No. 6102484 Patent No. 5786795

[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 a portion of fossil fuel-derived carbon material with PKS carbon, 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 a portion of fossil fuel-derived carbon material is replaced with PKS carbon based on the sintering ore manufacturing method described in Patent documents 1 and 2 at present, 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 ore even when PKS carbon is mixed into the sintered ore to reduce carbon dioxide emissions, and concentrate ore is mixed into the sintered ore to increase the total Fe content.

[0010] The means for solving 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 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. [2] The method for producing sintered ore according to [1], wherein in the raw material blending step, palm kernel shell charcoal having an arithmetic mean particle size of 1.10 mm or less is blended. [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 so 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 with the solid carbon material so that the blending ratio of the palm kernel shell charcoal to the solid carbon material is 10.0 to 50.0% by mass.

[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.

[0012] This is a diagram illustrating the method for manufacturing sintered ore according to this embodiment. This is a diagram illustrating an example of a sintered ore manufacturing facility to which the method for manufacturing sintered ore according to this embodiment can be applied. This is a diagram illustrating the manufacturing of PKS coal and the method for adjusting the particle size.

[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-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 not easily agglomerating. 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 fossil fuel-derived carbon materials such as powdered coke and anthracite, and biomass-derived palm kernel shell charcoal (hereinafter referred to as PKS charcoal). In this embodiment, in order to reduce the amount of carbon dioxide emitted when manufacturing sintered ore, PKS charcoal is blended with fossil fuel-derived carbon materials. It is preferable that the arithmetic mean particle size (hereinafter simply referred to as average particle size) of PKS charcoal is smaller than the average particle size of powdered coke. This is to improve granulation properties. In addition, the surface of PKS charcoal is smooth and has few open pores, making it less able to retain moisture compared to powdered coke. Therefore, by crushing the PKS charcoal to reduce its particle size, the specific surface area is increased, allowing moisture to be retained on the surface of the PKS charcoal. Specifically, since the average particle size of powdered coke is about 1.20 mm, it is preferable to crush the PKS charcoal to reduce its average particle size to 1.10 mm or less, which is smaller than the average particle size of powdered coke. This is because when the average particle size of PKS coal exceeds 1.10 mm, the mass ratio of iron raw material in the granulated particles becomes excessively low, and the surface of the PKS coal cannot retain moisture, making it difficult to form granulated particles.

[0017] Furthermore, the proportion of PKS coal in the solid carbon material is preferably around 10.0 to 50.0%. This is because, as will be described later, if the proportion of PKS coal is less than 10.0%, it becomes difficult to agglomerate the concentrate ore when the iron raw material contains concentrate ore. If the proportion of PKS coal exceeds 50.0%, the high combustibility of PKS coal may cause an excessive decrease in the yield of sintered ore. Of the carbon materials described above, PKS coal corresponds to the first carbon material in this embodiment, and powdered coke and anthracite correspond to the second carbon material in this embodiment. PKS coal will be described later.

[0018] In the example shown in Figure 2, various raw materials are supplied in predetermined proportions from a hopper 1, which stores various raw materials, onto a conveyor (not shown), and then transported by the conveyor to a drum mixer 2.

[0019] In the drum mixer 2, each raw material is mixed, and water is added to the mixture of raw materials to adjust the humidity. A sintering raw material is then produced that contains granulated particles (sometimes called pseudo-particles) granulated to a predetermined average particle size. The sintering raw material is then transported by a conveyor to the surge hopper 3 and temporarily stored. The process of producing the sintering raw material as described above corresponds to the raw material blending process in this embodiment.

[0020] Returning to the explanation of Figure 1, the process proceeds from the raw material blending step S101 to the raw material layer formation step S102. In the raw material layer formation step, sintering raw materials are loaded 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 materials stored in the surge hopper 3 shown in Figure 2 are cut out by the drum feeder 4 and loaded onto the bed ore layer 6 via the chute 5. In this way, the raw material layer 7 is formed.

[0021] In the example shown in Figure 2, a bed ore hopper 8 is provided upstream of the surge hopper 3 in the direction of transporting the sintering raw material in the sintering machine 9. Bed ore is stored in the bed ore hopper 8. The bed ore is cut from the drum feeder of the bed ore hopper 8 and loaded onto the pallet 10 of the sintering machine 9 via a chute to form a bed ore layer 6.

[0022] A cutoff gate 11 is installed downstream of the surge hopper 3 in the direction of conveying the sintering raw materials, which levels the surface of the raw material layer 7 on the pallet 10 to make the thickness of the raw material layer 7 nearly uniform. By passing through the cutoff gate 11, a raw material layer 7 of a predetermined thickness is formed. The process of loading the raw material onto the pallet 10 and forming a raw material layer 7 of a predetermined thickness corresponds to the raw material layer formation process in this 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 raw 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, a plurality of 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 the air 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 raw 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 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. For this reason, from the perspective of carbon neutrality, if PKS charcoal, which is a biomass 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 carbonizing 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. Furthermore, as mentioned above, the surface of PKS coal is smooth with few open pores and does not easily retain moisture on its 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 agglomerated, improving the granulation properties of the sintering raw material.

[0028] (Method for manufacturing PKS coal and adjusting particle size) Figure 3 is a diagram illustrating the method for manufacturing PKS coal and adjusting particle size. In Figure 3, for example, first, PKS is carbonized at 1000°C for 1 hour (step S201). The carbonization method for 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. It should be noted that uncarbonized PKS is difficult to crush, but carbonization of PKS improves its pulverability after carbonization compared to before carbonization. To ensure the pulverability of PKS coal, the Hard Globe Grindability Index (HGI) of PKS coal is preferably 25 or higher, and more preferably 30 or higher, the same as the HGI of powdered coke. The HGI can be measured by the method described in JIS M 8801:2008. The HGI can be changed by changing 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 to increase the specific surface area of ​​the PKS coal, thereby making it easier to retain moisture on the surface of the PKS coal. 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 into the sintering raw material. 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 charcoal is sieved using a sieve with the same mesh size as the average particle size of the coke powder to separate it into PKS charcoal with a particle size greater than or equal to the average particle size of the coke powder and PKS charcoal 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 charcoal. For PKS charcoal 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 charcoal again. For PKS charcoal with a particle size less than the average particle size of the coke powder (Yes in step S203), the PKS charcoal is recovered as a charcoal material to be blended into the sintering raw material (step S204).

[0031] (Effects and Benefits) 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 and improve the granulation properties of the sintering raw material. In addition, because the PKS coal is crushed to reduce its particle size, it burns more easily compared to before crushing. Therefore, it is possible to suppress the remaining unburned coal 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 coal material is replaced with PKS coal, the amount of carbon dioxide emitted in the sintering process can be reduced.

[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 charcoal. Next, the PKS charcoal was crushed using a jaw crusher and a disc mill to produce three types of PKS charcoal A, B, and C with different average particle sizes. Powdered coke was also prepared as a fossil fuel-derived charcoal material. The particle size distribution of powdered coke and each of the PKS charcoals A, B, and C is summarized in Table 1. In the following description, "mass %" will simply be written as "%".

[0033]

[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 is per gram, and the volume of open pores in powdered coke per unit mass is 0.67 cm³. ３ The value was / g. Thus, the volume of open pores in each PKS coal A, B, and C per unit mass is less than the volume of open pores in powdered coke per unit mass.

[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, and 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]

[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]

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

[0040]

[0041] (Evaluation) Experimental Example 1, Experimental Example 2, and Comparative Example 1 are examples where the blending ratio of the concentrated ore in the carbon material is 5.0%, and the types of PKS carbon, i.e., the particle sizes, are different from each other. In Experimental Example 1, Experimental Example 2, and Comparative Example 1, as shown in Table 4, it was found that the harmonic mean diameter of the granulated particles decreased with an increase in the particle size of the PKS carbon. The harmonic mean diameter of the granulated particles in Comparative Example 1 is less than 0.60 mm, and fine particles invade the voids through which air can pass when filled. As a result, it is considered that the voids are blocked, leading to a deterioration in the air permeability of the raw material layer on the pallet of the sintering machine.

[0042] Experimental Examples 2 to 4 are examples where the blending ratio of the concentrated ore was increased to 5.0%, 20.0%, and 30.0%, and the type and blending ratio of the PKS carbon were kept constant. In Experimental Examples 2 to 4, the harmonic mean diameter decreased with an increase in the blending ratio of the concentrated ore. In Experimental Example 4, although the harmonic mean diameter is 0.60 mm or more, among Experimental Examples 2 to 4, the particle size of the granulated particles is the smallest and closest to the threshold value (harmonic mean diameter of 0.60 mm). Therefore, it is considered preferable that the blending ratio of the concentrated ore is 30.0% or less with respect to the powdered iron ore.

[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 carbon was increased compared to Experimental Example 4. As shown in Table 4, the harmonic mean diameter of the granulated particles in Comparative Example 2 was 0.57 mm, which was smaller than the harmonic mean diameter of the granulated particles in Experimental Example 4. This is considered to be due to an increase in the particle size of the PKS carbon. Also, in Comparative Example 2, since the harmonic mean diameter is less than 0.60 mm, it is considered that, similar to Comparative Example 1, there is a deterioration in the air permeability of the raw material layer on the pallet of the sintering machine.

[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 blending ratio of PKS charcoal 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 blending ratio of PKS charcoal was 50.0%. In Experimental Example 3, Experimental Example 5, and Experimental Example 6, as shown in Table 4, the harmonic mean diameter of the granulated particles increases as the blending ratio of PKS charcoal increases. From this result, it is considered that the granulation property improves as the blending ratio of PKS charcoal increases.

[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 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 was smaller than the harmonic mean diameter of the granulated particles in Experimental Example 6. This is considered to be due to an increase in the particle size of PKS charcoal. In addition, in Comparative Example 3, since the harmonic mean diameter is less than 0.60 mm, it is considered that, similar to Comparative Example 1, the air permeability of the raw material layer has deteriorated on the pallet of the sintering machine.

[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. That is, the granulated particles of Experimental Examples 1 to 6 and Comparative Examples 1 to 3 were charged into a batch-type sintering pot test apparatus (hereinafter simply referred to as the apparatus) and fired. In this way, sintered ores of Experimental Examples 1 to 6 and Comparative Examples 1 to 3 were produced respectively. The above-mentioned apparatus has a raw material charging part with a diameter of 300 mm and a height of 400 mm, and is equipped with a ignition furnace and exhaust gas facilities such as a wind box and a blower. Therefore, it is possible to conduct a production test of sintered ore simulating an actual sintering machine.

[0047] After firing, the sintered ore was taken out from the apparatus, and the yield and productivity of the sintered ore were measured respectively. Here, the yield means the mass ratio of the sintered ore having a particle size of 5.00 mm or more in the total amount of the sintered ore, which was obtained by dropping the sintered ore from a height of 2 m onto the placement surface 4 times and pulverizing it. The productivity is a value obtained by dividing the amount of the sintered ore having a particle size of 5.00 mm or more by the time required for the production of the sintered ore and the area of the raw material layer in the apparatus. A larger value means better productivity. The yields and productivities of the sintered ores of Experimental Examples 1 to 6 and Comparative Examples 1 to 3 are summarized in Table 5.

[0048]

[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 the 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 the 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 when the particle size of PKS coal decreases, the specific surface area of ​​the PKS coal increases accordingly. This is thought to be due to an improvement in the combustion rate of the 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 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 firing 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, it was found that while the production rate improved with increasing PKS coal content, the yield decreased. The reason for the increased production rate is examined. PKS coal has higher combustibility than powdered coke. Therefore, it is thought that increasing the PKS coal content improves the firing rate in the raw material layer. The reason for the decreased yield is also examined. As mentioned above, PKS coal has higher combustibility than powdered coke. This means that the PKS coal burns at a high rate. On the other hand, the high burning rate may lead to increased incomplete combustion of the 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, these results suggest that the PKS coal content in the charcoal material should preferably 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 thought to be 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.

[0055] 1 Hopper 2 Drum mixer 3 Surge hopper 4 Drum feeder 5 Chute 6 Substrate layer 7 Raw material layer 8 Substrate layer hopper 9 Sintering machine 10 Pallet 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 mixing process S2 Raw material layer formation process S3 Sintering process

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 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 claim 1, wherein the raw material blending step includes blending the 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 any one of claims 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.

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