Method for manufacturing sintered ore

Abstract

This invention provides a method for manufacturing sintered ore, which maintains good reducibility even when using ore with low water of crystallization content, by forming a predetermined amount of pores internally. The method comprises a sintering raw material containing 15.0% by mass or more of iron ore, wherein the total water of crystallization in the total iron ore is 0.0% by mass or more but less than 3.0% by mass. The iron ore has an iron content of 58.00% by mass or more, a water of crystallization content of 4.00% by mass or more but less than 9.00% by mass, an Al2O3 content of 2.00% by mass or more, and a SiO2 content of less than 5.00% by mass. The average particle size of the total iron ore in the sintering raw material is 2.0 mm or less.

Description

[Technical Field]

[0001] This invention relates to a method for manufacturing sintered ore from sintering raw materials containing iron ore. [Previous Technology]

[0002] Sintered ore, which belongs to the raw materials of blast furnace ironmaking, is manufactured by sintering raw materials containing iron ore powder, limestone and other by-products, and coke and other carbon materials. Iron ore, which belongs to the raw materials, exists in various varieties with different compositions or particle sizes, and multiple varieties of iron ore are mixed as sintering raw materials.

[0003] Iron ore used in Japan is broadly categorized into: hematite and magnetite from South America, hematite from Australia, pisolite ore, and Marramanba ore. Regarding Australian iron ore, since the 2000s, with the depletion of hematite, the use of pisolite ore has expanded. Since then, Australian pisolite ore has been widely used as iron ore. In recent years, Australian pisolite ore has also become depleted, and Australian iron ore is being replaced by Marramanba ore. In addition, although South American iron ore has a high Fe content and is of high quality, its remote location presents transportation cost issues. In the future, with the depletion of Australian pisolite ore, it is predicted that the use of South American iron ore and Australian Marramanba ore as sintered ore will expand. The properties and composition of various iron ores are shown in Table 1.

[0004] [Table 1] iron ore Iron content [quality%] SiO2 content [quality%] Al2O3 content [quality%] Micron content [quality%] Water of crystallization content [quality%] Australian pebbles A 56.50 6.50 1.70 0 10.09 Australian Mara Mamba Mine B 60.50 4.40 2.35 31 5.94 High-quality micronized mineral C 65.80 4.70 0.16 35 0.24 Australian pebbles D 56.00 5.70 3.20 4 9.90 South American Mine E 62.85 4.95 1.35 34 2.85 South American mine F 65.00 1.90 1.40 18 3.20 South American mine G 62.00 7.50 0.70 55 1.66

[0005] As shown in Table 1, compared to pebbles, the Maramanba mineral series contains more micron powder with a diameter of less than 0.15 mm. Furthermore, compared to pebbles, the Maramanba mineral series contains less water of crystallization. In view of these factors, development is being carried out on sintering using Maramanba mineral as sintering raw material with the aim of improving productivity by enhancing the permeability of the sintering raw material and increasing the strength of the sinter.

[0006] Patent Document 1 discloses a method for preventing problems caused by the particle size of Malamamba ore by setting the blending rate of Malamamba ore in the total iron ore to 70% by mass or less. According to Patent Document 1, by limiting the blending rate of Malamamba ore, the proportion of fine-grained ore with a particle size of 0.25 mm or less can be limited, thereby suppressing the impact on productivity. Furthermore, under this condition, by setting the blending rate of hematite or magnetite to 20% by mass or more, high-strength sinter can be obtained with good productivity.

[0007] Patent Document 2 discloses a method for obtaining sinter with high cold-rolled strength with good productivity by blending multiple iron ores in such a way that the average porosity of the iron ores is less than 0.09 cm3 / g. According to Patent Document 2, even when using Maramanba ore, high-strength sinter can still be obtained with good productivity by limiting the average porosity of the iron ores.

[0008] Patent Document 3 also discloses a method for manufacturing sintered ore. Specifically, firstly, pebbles are added to Maramamba ore to produce a blend with SiO2 content of 3.0-5.0% by mass and micropowder content of less than 0.5 mm of less than 30% by mass. Water content of 5-10% by mass is added, and the blend is granulated using a high-speed mixer. Then, the method for manufacturing sintered ore discloses adding solid fuel and other ores, mixing and granulating again, and then sintering. According to Patent Document 3, adding porous pebbles to Maramamba ore, adding an appropriate amount of water, and performing mixing and granulation using a high-speed mixer allows some Maramamba ore micropowder to adhere to the open pores of the pebbles, resulting in a mixed granulated product with less micropowder. The results show that simulated particle size or simulated particle strength is improved, air permeability during sintering is increased, and productivity or finished product yield is improved. [Prior Art Documents] [Patent Documents]

[0009] Patent Document 1: Japanese Patent No. 5004421; Patent Document 2: Japanese Patent No. 4661154; Patent Document 3: Japanese Patent Application Publication No. 2004-137575 [Summary of the Invention]

[0010] (Problem to be Solved by the Invention) As disclosed in Patent Documents 1-3, the conventional technology for manufacturing sinter using Maramanba ore is developed to improve the permeability of sintering raw materials, the productivity of sinter, and the strength of sinter during the sintering process. On the other hand, the effect of the reducibility of sinter manufactured using Maramanba ore on its suitability for blast furnace operation has not yet been developed. The reducibility of sinter is a factor that has a significant impact on blast furnace operation. In particular, when the reducibility of sinter decreases, the proportion of reducing material in the blast furnace increases, leading to increased CO2 emissions and higher costs for reducing materials. For this reason, a high reducibility is required for sinter used as a blast furnace feedstock.

[0011] Therefore, the inventors investigated the effect of using Maramamba ore on the reducibility of sinter. The results confirmed that sinter produced using Maramamba ore has lower porosity and lower reducibility compared to sinter produced using pebbles. Furthermore, when sinter is produced using both South American ore and Maramamba ore, which have a lower water of crystallization content than Maramamba ore, its reducibility is further reduced.

[0012] Here, regarding the manufacture of sinter using iron ore, the water of crystallization contained in the iron ore will detach from the iron ore during the heating process of sintering, and form pores inside the iron ore. Therefore, the higher the water of crystallization content of the iron ore, the higher the porosity of the manufactured sinter, which will improve the reducibility of the sinter when applied to blast furnace operation.

[0013] In view of this, it is predicted that the water content of iron ore used in sintering processes will continue to decrease as pebbly ore with a higher water content of crystallization becomes depleted. Therefore, it is also predicted that it will be more difficult to manufacture sinter that meets the requirements of high reducibility. Therefore, regarding the manufacture of sinter, it is required to develop a method for manufacturing sinter that can still form a certain amount of porosity even when using Maramanba ore, which has a lower water content of crystallization than pebbly ore.

[0014] This invention was made in view of these circumstances, and its object is to provide a method for manufacturing sintered ore with good reducibility even when using ores with low water of crystallization content to manufacture sintered ore, by forming a predetermined amount of pores inside. (Technical means to solve the problem)

[0015] The main structure of the present invention that solves the above-mentioned problems is as follows. [1] A method for manufacturing sintered ore, comprising a sintering raw material containing 15.0% by mass or more of iron ore, wherein the total water of crystallization contained in the total iron ore is 0.0% by mass or more and less than 3.0% by mass, wherein the iron ore has an iron content of 58.00% by mass or more, a water of crystallization content of 4.00% by mass or more and less than 9.00% by mass, an Al2O3 content of 2.00% by mass or more, and a SiO2 content of less than 5.00% by mass; wherein the average particle size of the total iron ore contained in the sintering raw material is 2.0 mm or less. [2] The method for manufacturing sintered ore as described in [1], wherein the amount of coke powder contained in the sintering raw material is less than 4.0% by mass. [3] The method for manufacturing sinter as described in [1] or [2], wherein the formulation of the sintering raw material is adjusted such that the CaO content of the sintering ore is 11.0% by mass or more. (Effects compared to prior art)

[0016] Even when sinter is manufactured using ores with low water of crystallization content, its reducibility remains good due to the formation of a predetermined amount of pores inside.

Implementation Method

[0017] Hereinafter, the present invention will be described through embodiments thereof.

[0018] In the manufacture of sinter, when Maramamba ore is used instead of pebbles, the total amount of water of crystallization inside the sintering raw material is less compared to the case where pebbles are used. Therefore, it has been found that when this raw material is sintered using a sintering process, the reducibility of the sinter decreases due to the reduced porosity inside the sinter. Therefore, even when Maramamba ore is used in the manufacture of sinter, in order to form a certain amount of porosity inside and obtain a sinter with good reducibility, it is necessary to perform porosity formation by other methods in addition to the porosity formed by the water of crystallization contained in the iron ore.

[0019] Here, it is known that the porosity of sinter is affected not only by the crystal water content of the iron ore used, but also by the particle size of the iron ore and the amount of fuel such as coke blended in the sintering raw materials. Therefore, even when using Maramanba ore, in order to form a certain amount of porosity inside the sinter, it is necessary to review the particle size and blending conditions of the iron ore in the sintering raw materials supplied to the sintering process.

[0020] In view of this, the inventors prepared a sintering raw material by blending various iron ores such as Maramamba ore, and provided the sintering raw material to a sintering process to produce sintered ore. They then conducted in-depth research on the effects of iron ore particle size and the amount of fuel such as coke on the sintered ore. They then discovered a method for producing sintered ore with good reducibility even when using Maramamba ore, which has a lower water content than pebbles, by forming a predetermined amount of pores inside.

[0021] Furthermore, the inventors, through their review, discovered that for sintered ore using pebbles, the JIS-RI (reducibility index) must be 65% or higher, and that to obtain sintered ore with a JIS-RI of 65% or higher, the porosity of the sintered ore must be set to 20% or higher. In other words, it was found that in order to manufacture sintered ore with the same reduceability as conventionally used pebbles, a manufacturing method with a porosity of 20% or higher is necessary. Here, the JIS-RI for reduceability refers to the "achievement of JIS reduction rate RI" as specified in "JIS M8713". The manufacturing method of the sintered ore of the present invention will be described below.

[0022] The method for manufacturing sintered ore of the present invention involves blending iron ore with 15.0% or more by mass into the sintering raw material. The iron ore has an iron content of 58.00% or more by mass, a water content of 4.00% or more by mass but less than 9.00% by mass, an Al2O3 content of 2.00% or more by mass, and a SiO2 content of less than 5.00% by mass.

[0023] Iron ore with an iron content of 58.00% by mass or more, a water of crystallization content of 4.00% by mass or more but less than 9.00% by mass, an Al2O3 content of 2.00% by mass or more, and a SiO2 content of less than 5.00% by mass, as shown in Table 1, refers to Maramanba ore. Furthermore, Maramanba ore is used to replace pebbles; therefore, the amount of Maramanba ore in the sintering raw materials is set to 15% by mass or more.

[0024] Furthermore, in this invention, sintered ore is manufactured from sintering raw materials containing a total water of crystallization of 0.0% or more but less than 3.0% by mass in the total iron ore. That is, in the case of low total water of crystallization content in the sintered raw materials, this invention employs methods for forming pores in the manufactured sinter, in addition to pores formed due to the water of crystallization content of the iron ore (Maramanba ore), using methods performed according to other methods. Therefore, a porosity of 20% by volume or more can be achieved, resulting in sintered ore with good reducibility.

[0025] In the method for manufacturing sintered ore of the present invention, the average particle size of the total iron ore mixed in the sintering raw material is set to be 2.0 mm or less.

[0026] By setting the average particle size of all iron ore (including Maramanba ore) incorporated into the sintering raw materials to 2.0 mm or less, uniform and fine pores can be formed inside the sinter after the sintering process, and pore loss during the crushing of the sinter can be suppressed. Therefore, the amount of residual pores in the finished sinter increases, and a sinter with a porosity of 20% by volume or more and a JIS-RI of 65% or more of reduction can be obtained. Here, the average particle size of the iron ore can also be the arithmetic mean diameter of all iron ore particles incorporated into the formulation raw materials. Furthermore, the JIS-RI of reduction can also be the "achievement of JIS reduction rate RI" as specified in "JIS M8713".

[0027] As described above, by employing the sinter manufacturing method of the present invention, even when using ore with low crystal water content to manufacture sinter, its reducibility remains good by forming a predetermined amount of pores inside.

[0028] Furthermore, in this invention, it is preferable to set the amount of coke powder incorporated into the sintering raw material to be 3.5% by mass or more but less than 4.0% by mass. By limiting the amount of solid fuel (coke powder) burned in the sintering process, excessive generation of melt inside the sinter cake during the sintering process is suppressed, thereby suppressing the blockage of pores as the melt permeates. Therefore, the sintered ore after the sintering process can have increased porosity and improved reducibility of the blast furnace feedstock used in blast furnace operation. In this case, the porosity of the sintered ore after the sintering process can be increased to 27% by volume or more, and the JIS-RI of reducibility can be increased to 70% or more.

[0029] Here, when examining the application of sinter in blast furnace operation, it is preferable to also examine the low-temperature reduction pulverization property of the sinter. Low-temperature reduction pulverization property is used as an indicator of deterioration in productivity and energy efficiency during blast furnace operation. More specifically, sinter in the blast furnace will pulverize in the initial stage of the reduction reaction. Moreover, the pulverization process deteriorates the ventilation within the furnace, leading to an unstable blast furnace operation. Therefore, low-temperature reduction pulverization property is used as an indicator of the pulverization property of sinter in the blast furnace during the initial stage of reduction.

[0030] Furthermore, it is known that the low-temperature reductive pulverization property of sinter has an inverse relationship with the reducibility of blast furnace feedstock when used in blast furnace operation. That is, increasing the porosity of sinter will improve the reducibility of blast furnace feedstock, but on the other hand, it may induce reductive pulverization of sinter. Therefore, in the production of sinter, it is preferable to increase the porosity of the sinter to improve the reducibility of blast furnace feedstock while suppressing the low-temperature reductive pulverization property of the sinter.

[0031] The inventors have also conducted in-depth research on a method for manufacturing sinter that increases the porosity of the sinter to improve the reducibility of the blast furnace feedstock and suppresses low-temperature reductive pulverization. Therefore, it has been found that the low-temperature reductive pulverization of sinter depends on the blending conditions of various raw materials in the sintering feedstock before the sintering process.

[0032] In view of this, in order to suppress the low-temperature reductive pulverization of sinter, it is preferable to adjust the formulation of the sintering raw materials so that the CaO content of the sinter is 11.0% by mass or more. Specifically, the CaO content in the sintering raw materials is increased by adjusting the blending ratio of limestone or quicklime contained in the sintering raw materials. The reason is that by increasing the CaO content in the sintering raw materials, calcium ferrite formation is promoted during the sintering process, thereby suppressing the formation of hematite, which is the cause of low-temperature reductive pulverization. Furthermore, when the CaO content of the sintering ore is excessively increased, the amount of slag generated in the blast furnace increases, which leads to a decrease in the energy efficiency during blast furnace operation. Therefore, it is preferable to adjust the CaO content in the sintering raw materials to a level that suppresses low-temperature reductive pulverization and is 12.0% by mass or less.

[0033] Therefore, the average particle size of the iron ore (Maramanba ore) and other iron ores blended in the sintering raw materials is set to 2.0 mm or less, and the blending amount of coke powder blended in the same sintering raw materials is set to less than 4.0% by mass. Furthermore, the formulation of the sintering raw materials is adjusted so that the CaO content of the sinter is 11.0% by mass or more. In this way, a sinter with a porosity of 27% by volume or more, a JIS-RI of reducibility of 70% or more, and a low-temperature reductive pulverization RDI of less than 30% can be obtained. That is, a sinter that balances good reducibility and suppression of low-temperature reductive pulverization can be obtained. Here, the low-temperature reductive pulverization RDI can also be the "reduction pulverization index RDI" specified in "JIS M8720". In addition, the reduction pulverization index RDI of sinter produced using pebbles is approximately 30%. Therefore, by adjusting the CaO content of the sinter to a predetermined value, the low-temperature reduction pulverization can be suppressed compared to the case of manufacturing using pebbles.

[0034] The method for manufacturing sintered ore of the present invention can also be implemented as follows. First, a few percent of water is added to iron ore powder, limestone and other by-products containing CaO, silica and other by-products containing SiO2, and coke and other charcoal materials, and the mixture is then mixed and granulated to obtain simulated particle-based sintering raw materials. Second, the simulated particle-based sintering raw materials are filled onto the furnace bed to form a raw material layer, and the surface of the raw material layer is ignited. Then, while air is drawn downwards, the charcoal materials are burned below, and the heat of combustion of the charcoal materials is used to sinter the sintering raw materials to produce sinter cakes. Then, the produced sinter cakes are crushed and granulated, and particles larger than a predetermined size are used as raw materials for blast furnace ironmaking. [Example]

[0035] Hereinafter, embodiments of the method for manufacturing sintered ore using the present invention will be described.

[0036] A few percentages of water are added to various iron ore powders, limestone and other CaO-containing by-products, silica and other SiO2-containing by-products, and coke and other carbon-containing formulation raw materials, and then mixed and granulated to obtain simulated particle-based sintering raw materials. Sintering tests are conducted on the simulated particle-based sintering raw materials using a cylindrical sintering test pot with a diameter of 300 mm. A 20 mm layer of sintered ore is filled as a bottom layer on the furnace bed inside the cylindrical sintering test pot, and then the simulated particle-based sintering raw materials are filled on top as a sintering raw material layer. The carbon material contained in the top layer of the filled sintering raw material is ignited, and air is drawn downwards while the carbon material is burned downwards. The combustion heat of the carbon material is used to sinter the sintering raw material layer to obtain a sintered cake. The raw material admixture amount, average particle size of the total iron ore, total crystal water admixture amount, and target composition of the sintered ore (sintered ore composition) in each embodiment are shown in Table 2. Furthermore, the sintering conditions of the sintering process in each embodiment are shown in Table 3. Here, the total water of crystallization content refers to the amount of total water of crystallization contained in the total iron ore in the sintering raw material among all the raw materials listed as raw material admixtures.

[0037] [Table 2] Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Invention Example 1 Invention Example 2 Invention Example 3 Invention Example 4 Raw material blending amount [quality%] Australian pebbles A 31.6 31.8 0.0 0.0 0.0 0.0 0.0 0.0 Australian Mara Mamba Mine B 0.0 0.0 31.2 18.9 22.5 22.6 25.4 25.5 High-quality micronized mineral C 0.0 0.0 0.0 0.0 10.3 10.4 6.4 6.4 Australian pebbles D 6.3 6.4 6.3 6.3 0.0 0.0 6.4 6.4 South American Mine E 25.3 25.5 25.0 25.1 32.7 33.0 25.4 25.6 South American mine F 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 South American mine G 0.0 0.0 0.0 12.6 0.0 0.0 0.0 0.0 Silicon 0.0 0.0 0.7 0.3 0.1 0.1 0.7 0.7 quicklime 0.0 1.0 0.0 1.0 1.9 1.9 1.9 1.9 Return to ore 19.1 19.0 19.1 19.1 19.2 19.2 19.1 19.2 limestone 13.4 12.0 13.4 12.4 9.0 9.1 10.4 10.5 Powdered coke 4.3 4.3 4.3 4.3 4.3 3.7 4.3 3.8 Total water of crystallization [mass %] 4.5 4.7 3.2 2.7 2.3 2.3 2.9 2.9 Average particle size of total iron ore [mm] 3.5 3.5 2.2 2.1 1.8 1.8 2.0 2.0 Composition of sintered ore [quality%] CaO 11.0 10.8 11.0 11.2 10.0 10.0 11.0 11.0 SiO2 5.8 5.7 5.8 5.6 5.0 5.0 5.8 5.8

[0038] [Table 3] Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Invention Example 1 Invention Example 2 Invention Example 3 Invention Example 4 Sintering steps Layer thickness [mm] 380 380 380 380 580 580 380 380 Negative pressure during calcination [kPa] 10.0 7.7 10.0 7.7 10.5 10.5 10.0 10.0

[0039] Then, by dropping the obtained sinter cake from a height of 2m four times to break it into pieces, sinter with a diameter of 5mm or larger was recovered and used for the evaluation of reducibility, porosity, and low-temperature reductive pulverization. The evaluation of the reducibility of the sinter was conducted by measuring the reduction rate RI as specified in JIS M8713. The evaluation of the low-temperature reductive pulverization of the sinter was conducted by measuring the reductive pulverization index RDI as specified in JIS M8720. The evaluation of the porosity of the sinter was conducted by first measuring its apparent density using the water utilization liquid weighing method, and then measuring the apparent density by boiling the sinter after crushing it and passing it through a sieve with a mesh size of 250μm. Then, based on the actual density obtained from the measurement results, the porosity of the sinter was calculated from the pore volume per unit volume of the sinter. The evaluation results of the sinter are shown in Table 4.

[0040] [Table 4] Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Invention Example 1 Invention Example 2 Invention Example 3 Invention Example 4 Sintered ore Porosity [volume %] 24.8 26.0 21.9 17.9 22.2 28.2 26.4 29.3 Reduceability [%] 74.8 71.1 70.4 64.0 68.9 73.1 69.8 73.3 Low-temperature reducing pulverization [%] 28.8 31.9 30.7 30.8 35.8 31.2 25.4 26.2

[0041] Comparative Examples 1 and 2 are examples of manufacturing sinter by incorporating pebbles into the sintering raw materials. Since pebbles were used in Comparative Examples 1 and 2, as shown in Table 4, they exhibited a porosity of 20% by volume or more and a reducibility of 65% or more. Furthermore, since pebbles were used in Comparative Examples 1 and 2, the reduction pulverization index (RDI) was approximately 30% in both cases.

[0042] Comparative Examples 3 and 4 are examples of manufacturing sinter by incorporating Maramamba ore into the sintering raw materials. The porosity and reducibility values ​​of Comparative Examples 3 and 4 are lower than those of Comparative Examples 1 and 2. Although Comparative Example 3 uses Maramamba ore, the total water of crystallization content exceeds 3% by mass, therefore the porosity is 20% by volume or more, and the JIS-RI is 65% or more. Furthermore, Comparative Example 4 has a total water of crystallization content of less than 3% by mass (refer to Table 2), therefore exhibiting a porosity of less than 20% by volume and a reducibility of less than 65%. That is, it can be confirmed that when Maramamba ore is incorporated and the total water of crystallization content is relatively low, the porosity decreases to less than 20%, and the JIS-RI decreases to less than 65%.

[0043] Example 1 of the invention is an embodiment in which Maramanba ore is blended into sintering raw materials, and when the total crystal water content is less than 3.0% by mass, the average particle size of the total iron ore blended in the sintering raw materials is set to 2.0 mm or less to produce sintered ore. In Example 1 of the invention, although the total crystal water content is relatively small, at 2.3% by mass, it still exhibits a porosity of 20% by volume or more and a reducibility of 65% or more. That is, it has been confirmed that by blending Maramanba ore into sintering raw materials and setting the average particle size of the total iron ore blended in the sintering raw materials to 2.0 mm or less, a certain amount of pores are formed inside the produced sintered ore, thereby obtaining good reducibility. The reason for this can be considered to be that by refining the particle size of the iron ore, the amount of residual pores in the finished sintered ore after crushing can be increased.

[0044] In Invention Example 2, Maramanba ore is blended into the sintering raw material. When the total crystal water content is less than 3.0% by mass, the average particle size of the total iron ore blended in the sintering raw material is set to 2.0 mm or less, and the content of coke powder blended in the sintering raw material is set to less than 4.0% by mass to produce sintered ore. In Invention Example 2, the porosity is 27% by volume or more and the reducibility is 70% or more. That is, Maramanba ore is blended into the sintering raw material, and the average particle size of the total iron ore blended in the sintering raw material is set to 2.0 mm or less, and the content of coke powder blended in the sintering raw material is set to less than 4.0% by mass. Therefore, it can be confirmed that the porosity and reducibility of the sintered ore after the sintering process are improved. The reason can be considered to be that by limiting the content of coke powder blended to less than 4.0% by mass, the blockage of pores due to the molten metal can be suppressed.

[0045] In Invention Example 3, Maramamba ore is blended into the sintering raw material. When the total crystal water content is less than 3.0% by mass, the average particle size of the total iron ore blended in the sintering raw material is set to 2.0 mm or less, and the CaO content of the sintering ore is adjusted to 11.0% by mass or more. In Invention Example 3, the CaO content of the sintering ore is set to 11.0% by mass or more, therefore, the amount of limestone blended is greater than that in Invention Examples 1 and 2. In Invention Example 3, similar to Invention Example 1, the porosity is about 20% by volume or more, and the reducibility is 65% or more. Furthermore, compared to Invention Example 1, Invention Example 3 can suppress low-temperature reduction pulverization. Specifically, the low-temperature reduction pulverization is less than 30%, which is a better result than that in Comparative Examples 1 and 2, which use pebbles. In other words, by incorporating Maramanba ore into the sintering raw materials and setting the average particle size of the total iron ore in the sintering raw materials to be less than 2.0 mm, and by adjusting the formulation of the sintering raw materials so that the CaO content of the sintering ore is 11.0% by mass or more, the formulation of the sintering raw materials is adjusted. Therefore, it can be confirmed that the sintering ore produced by the sintering process can achieve good reducibility by forming a predetermined amount of pores inside, and the low-temperature reduction pulverization of the sintering ore can be suppressed.

[0046] In Invention Example 4, Maramamba ore is blended into the sintering raw material. When the total crystal water content is less than 3.0% by mass, the average particle size of the total iron ore blended in the sintering raw material is set to 2.0 mm or less, and the content of coke blended in the sintering raw material is adjusted to less than 4.0% by mass. Furthermore, the formulation of the sintering raw material is adjusted so that the CaO content of the sintering ore is 11.0% by mass or more, in order to produce sintering ore. In Invention Example 4, the CaO content of the sintering ore is set to 11.0% by mass or more, therefore, the amount of limestone blended is greater than that in Invention Examples 1 and 2. In Invention Example 4, similar to Invention Example 2, the porosity is about 27% by volume or more, and the reducibility is 70% or more. Moreover, compared to Invention Example 2, Invention Example 4 can suppress low-temperature reduction pulverization. Specifically, the low-temperature reduction pulverization is less than 30%, which is a better result than that in Comparative Examples 1 and 2, which use pebbles. That is, by blending Maramanba ore into the sintering raw materials, setting the average particle size of the total iron ore blended in the sintering raw materials to be less than 2.0 mm, and setting the blending amount of pulverized coke to be less than 4.0% by mass, the formulation of the sintering raw materials is adjusted so that the CaO content of the sintering ore is 11.0% by mass or more. Then, for the sintering ore after the sintering process, it can be confirmed that the porosity and reducibility are improved, and the low-temperature reductive pulverization of the sintering ore can be suppressed.

Claims

1. A method for manufacturing sintered ore, comprising a method for manufacturing sintered ore from a sintering raw material containing 15.0% by mass or more of iron ore, wherein the total water of crystallization in the total iron ore contains 0.0% by mass or more and less than 3.0% by mass; wherein the iron ore has an iron content of 58.00% by mass or more, a water of crystallization content of 4.00% by mass or more and less than 9.00% by mass, an Al2O3 content of 2.00% by mass or more, and a SiO2 content of less than 5.00% by mass; wherein, The average particle size of the total iron ore mixed in the above-mentioned sintering raw materials is less than 2.0 mm.

2. The method for manufacturing sintered ore as described in claim 1, wherein, The amount of powdered coke added to the above sintering raw materials is less than 4.0% by mass.

3. The method for manufacturing sintered ore as described in claim 1 or 2, wherein, The formulation of the above-mentioned sintering raw materials is adjusted so that the CaO content of the sintered ore is 11.0% by mass or more and 12.0% by mass or less.