Sinter manufacturing method

Abstract

To provide a method for producing sintered ore that has good reducibility by forming a predetermined amount of pores inside the sintered ore even when the sintered ore is produced using ore with a low content of water of crystallization. A method for producing sintered ore from a sintering raw material that contains 15.0 mass% or more of iron ore having an iron content of 58.00 mass% or more, a crystal water content of 4.00 mass% or more but less than 9.00 mass%, an Al2O3 content of 2.00 mass% or more, and an SiO2 content of less than 5.00 mass%, and in which the total crystal water contained in the total iron ore blended is 0.0 mass% or more but less than 3.0 mass%, wherein the average particle size of all the iron ores blended in the sintering raw material is 2.0 mm or less.

Description

[Technical Field]

[0001] The present invention relates to a method for producing sintered ore from sinter raw materials containing iron ore. [Background technology]

[0002] Sinter, a raw material used in blast furnace ironmaking, is produced by sintering raw materials that include iron ore powder, auxiliary materials such as limestone, and carbonaceous materials such as coke. There are many different brands of iron ore with different compositions and particle sizes, and multiple brands of iron ore are blended to produce the sinter raw material.

[0003] Iron ore used in Japan can be broadly divided into South American hematite and magnetite ores, and Australian hematite, pisolite, and Marra Mamba ores. As hematite ore began to become depleted in the 2000s, the use of Australian pisolite ore expanded. Since then, Australian pisolite ore has been widely used as iron ore. In recent years, Australian pisolite ore is also becoming depleted, and Australian iron ore is being replaced by Marra Mamba ore. South American iron ore is high-quality and has a high iron content, but its remote location poses transportation costs. As Australian pisolite ore becomes depleted, the use of South American iron ore and Australian Marra Mamba ore as sinter is expected to expand. Table 1 shows the properties and compositions of various iron ores.

[0004] [Table 1]

[0005] As shown in Table 1, Marra Mamba ore has a higher content of fine particles with a diameter of 0.15 mm or less than pisolite ore. Marra Mamba ore also has a lower content of crystal water than pisolite ore. Based on these facts, development has been carried out for the sintering of sinter raw materials using Marra Mamba ore with the aim of improving productivity by improving the permeability of the sinter raw material, and also improving the strength of the sintered ore.

[0006] Patent Document 1 discloses a method for preventing problems caused by the particle size of Marra Mamba ore by setting the blending ratio of Marra Mamba ore to 70% by mass or less of the total iron ore. According to Patent Document 1, by limiting the blending ratio of Marra Mamba ore, the proportion of fine ore with a particle size of 0.25 mm or less can be limited, thereby suppressing the impact on productivity. Furthermore, under these conditions, it is stated that by setting the blending ratio of hematite ore or magnetite ore to 20% by mass or more, high-strength sintered ore can be obtained with good productivity.

[0007] Patent Document 2 states that the average pore volume of iron ore is 0.09 cm 3 Patent Document 2 discloses a method for obtaining sintered ore with high cold strength at good productivity by blending multiple iron ores so that the average porosity of the iron ore is 1 / g or less. Even when Marra Mamba ore is used, Patent Document 2 discloses that high-strength sintered ore can be obtained at good productivity by limiting the average porosity of the iron ore.

[0008] Patent Document 3 also discloses a method for producing sintered ore. Specifically, pisolite ore is first added to Marra Mamba ore to produce a blend containing 3.0 to 5.0% by mass of SiO2 and less than 30% by mass of fine powder of 0.5 mm or less. This blend is then mixed and granulated with 5 to 10% by mass of water using a high-speed agitator mixer. Solid fuel and other ores are then added, and the mixture is mixed and granulated again, followed by sintering. According to Patent Document 3, porous pisolite ore is added to Marra Mamba ore, and an appropriate amount of water is added. The mixture is then mixed and granulated using a high-speed agitator mixer. This process results in some of the fine powder of the Marra Mamba ore adhering to the open pores of the pisolite ore, resulting in a granulated mixture with minimal fine powder. This process improves the pseudoparticle size and strength, improves permeability during the sintering process, and improves productivity and product yield. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] Patent No. 5004421 [Patent Document 2] Patent No. 4661154 [Patent Document 3] Japanese Patent Application Laid-Open No. 2004-137575 Summary of the Invention [Problem to be solved by the invention]

[0010] As disclosed in Patent Documents 1 to 3, in the past, technologies have been developed for the production of sintered ore using Marra Mamba ore, to improve the permeability of the sintered raw material during the sintering process, to improve the productivity of sintered ore, and to improve the strength of sintered ore. However, no development has been done on the impact of sintered ore produced using Marra Mamba ore on reducibility when applied to blast furnace operation. The reducibility of sintered ore can be said to be a factor that significantly affects blast furnace operation. In particular, if the reducibility of sintered ore decreases, the reducing agent ratio in the blast furnace increases, leading to increased CO2 emissions and increased costs for reducing agents. For these reasons, sintered ore used as a raw material for blast furnaces requires high reducibility.

[0011] Therefore, the present inventors investigated the effect on reducibility of sintered ore produced using Marra Mamba ore. As a result, it was confirmed that sintered ore produced using Marra Mamba ore has lower porosity and lower reducibility than sintered ore produced using pisolite ore. It was also confirmed that when sintered ore is produced using Marra Mamba ore in combination with South American ore, which has a lower water of crystallization content than Marra Mamba ore, the reducibility is further reduced.

[0012] In the production of sintered ore using iron ore, the water of crystallization contained in the iron ore is released from the iron ore during the temperature rise process that accompanies the sintering process, forming pores inside the iron ore. Therefore, the higher the content of water of crystallization in the iron ore, the higher the porosity of the produced sintered ore, and the better the reducibility of the sintered ore when applied to blast furnace operation.

[0013] In light of this, it is expected that the amount of water of crystallization in iron ore used in the sintering process will continue to decrease as pisolite ore, which has a high water of crystallization, becomes increasingly depleted. Therefore, it is expected that it will become difficult to produce sintered ore that satisfies high reducibility. Therefore, there is a need to develop a method for producing sintered ore that can form a predetermined amount of pores inside, even when Marra Mamba ore, which has a lower water of crystallization than pisolite ore, is used.

[0014] The present invention has been made in view of the above circumstances, and aims to provide a method for producing sintered ore that has good reducibility by forming a predetermined amount of pores inside the sintered ore, even when the sintered ore is produced using an ore with a low content of water of crystallization. [Means for solving the problem]

[0015] The gist and configuration of the present invention to solve the above problems are as follows. [1] A method for producing sintered ore from a sintering raw material that contains 15.0 mass% or more of iron ore having an iron content of 58.00 mass% or more, a crystal water content of 4.00 mass% or more but less than 9.00 mass%, an Al2O3 content of 2.00 mass% or more, and an SiO2 content of less than 5.00 mass%, and the total crystal water contained in the total iron ore to be blended is 0.0 mass% or more but less than 3.0 mass%, wherein the average particle size of all the iron ores blended in the sintering raw material is 2.0 mm or less. [2] The method for producing sintered ore according to [1], wherein the amount of coke fines mixed in the sintering raw material is less than 4.0 mass %. [3] The method for producing sintered ore according to [1] or [2], wherein the blending of the sintering raw materials is adjusted so that the CaO content of the sintered ore is 11.0 mass % or more. [Effects of the Invention]

[0016] Even when sintered ore is produced using ore with a low content of water of crystallization, by forming a predetermined amount of pores inside the sintered ore, the reducibility is improved. DETAILED DESCRIPTION OF THE INVENTION

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

[0018] When Marra Mamba ore is used as a substitute for pisolite ore in the production of sintered ore, the total amount of crystallization water contained within the sinter raw material is lower than when pisolite ore is used. It has been discovered that, due to this, when the sinter raw material is sintered in a sintering process, the porosity within the produced sintered ore decreases, resulting in a decrease in the reducibility of the sintered ore. Therefore, even when Marra Mamba ore is used in the production of sintered ore, in order to form a predetermined amount of pores within the sintered ore and obtain sintered ore with good reducibility, it is necessary to form pores by other methods in addition to the formation of pores due to the crystallization water contained in the iron ore.

[0019] It is known that the porosity of sintered ore is affected not only by the water of crystallization content of the iron ore used, but also by the particle size of the iron ore and the amount of fuel such as coke breeze mixed in the sintering raw material. Therefore, even when Marra Mamba ore is used, in order to form a predetermined amount of pores inside the sintered ore, it is necessary to consider the particle size and mixing conditions of the iron ore in the sintering raw material used in the sintering process.

[0020] Based on these findings, the present inventors prepared sintering raw materials containing various iron ores, such as Marra Mamba ore, and subjected the sintering raw materials to a sintering process to produce sintered ore, and conducted extensive research into the effects of the particle size of the iron ore and the amount of fuel, such as coke fines, on the sintered ore.As a result, they discovered a method for producing sintered ore that has good reducibility by forming a predetermined amount of pores inside, even when producing sintered ore using Marra Mamba ore, which has a lower water of crystallization content than pisolite ore.

[0021] Furthermore, as a result of the inventors' investigations, they found that for sintered ore using pisolite ore, the JIS-RI, an index of reducibility, is 65% or more, and that to obtain sintered ore with a JIS-RI of 65% or more, the porosity of the sintered ore must be 20% or more. In other words, they found that a manufacturing method that achieves a porosity of 20% or more is required to produce sintered ore with reducibility equivalent to that of conventionally used pisolite ore. Here, JIS-RI as reducibility refers to the "achieved JIS reduction ratio RI" specified in "JIS M8713." The manufacturing method of sintered ore of the present invention is described below.

[0022] The method for producing sintered ore of the present invention comprises blending, as a raw material for sintering, 15.0% by mass or more of iron ore having an iron content of 58.00% by mass or more, a crystal water 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.

[0023] Iron ore with an iron content of 58.00% by mass or more, a crystal water 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 an SiO2 content of less than 5.00% by mass is called Marra Mamba ore, as shown in Table 1. Since Marra Mamba ore is used as a substitute for pisolite ore, the raw material blend amount of Marra Mamba ore in the sintering raw material is set to 15% by mass or more.

[0024] Furthermore, in the present invention, sintered ore is produced from a sintering raw material in which the total amount of crystal water contained in the total iron ore blended is 0.0% by mass or more but less than 3.0% by mass. That is, even when the total amount of crystal water blended inside the sintering raw material is low, the present invention employs a method for forming pores in the produced sintered ore by forming pores based on a method other than the formation of pores due to the crystal water content of the iron ore (Marra Mamba ore). This makes it possible to obtain sintered ore with a porosity of 20% by volume or more and good reducibility.

[0025] In the method for producing sintered ore according to the present invention, the average particle size of all iron ores blended in the sintering raw material is set to 2.0 mm or less.

[0026] By setting the average particle size of all iron ores (including Marra Mamba ore) blended into the sintering raw materials to 2.0 mm or less, the pores inside the sintered ore that has undergone the sintering process are uniform and fine, and the loss of pores during the sintering process can be suppressed. This increases the amount of pores remaining in the finished sintered ore, resulting in sintered ore with a porosity of 20% by volume or more and a JIS-RI of 65% or more, which indicates reducibility. Here, the average particle size of the iron ore may be the arithmetic mean diameter of all the iron ore particles blended into the raw materials. Furthermore, the JIS-RI, which indicates reducibility, may be the "achieved JIS reduction ratio RI" specified in "JIS M8713."

[0027] From the above, by using the method for producing sintered ore of the present invention, even when sintered ore is produced using ore with a low content of water of crystallization, a predetermined amount of pores can be formed inside the sintered ore, thereby improving reducibility.

[0028] Furthermore, in the present invention, it is preferable that the amount of coke fines blended into the sintering raw material be 3.5 mass% or more but less than 4.0 mass%. By limiting the amount of solid fuel (coke fines) burned during the sintering process in the sintering raw material, excessive production of molten liquid inside the sintered cake during the sintering process is suppressed, and pore blockage due to penetration of the molten liquid is suppressed. Therefore, the porosity of the sintered ore that has undergone the sintering process can be improved, and the reducibility of the blast furnace raw material when applied to blast furnace operation can be improved. In this case, the porosity of the sintered ore that has undergone the sintering process can be improved to 27% by volume or more, and the JIS-RI, which indicates reducibility, can be improved to 70% or more.

[0029] Here, when considering the application of sintered ore to blast furnace operation, it is preferable to also consider the low-temperature reduction disintegration of the sintered ore. Low-temperature reduction disintegration is used as an index of deterioration in productivity and energy efficiency in blast furnace operation. More specifically, sintered ore disintegrates in the early stage of the reduction reaction inside the blast furnace. As the disintegration progresses, the permeability inside the furnace deteriorates, resulting in unstable blast furnace operation. For this reason, low-temperature reduction disintegration is used as an index of the disintegration of sintered ore in the early stage of reduction inside the blast furnace.

[0030] It is known that the low-temperature reduction disintegration property of sintered ore is inversely related to the reducibility of the blast furnace raw material when applied to blast furnace operation. That is, while the amount of pores in sintered ore increases, improving the reducibility of the blast furnace raw material, there is a problem that reduction disintegration of the sintered ore is induced. Therefore, in the production of sintered ore, it is preferable to suppress the low-temperature reduction disintegration property of the sintered ore while increasing the amount of pores in the sintered ore to improve the reducibility of the blast furnace raw material.

[0031] The present inventors have conducted extensive research into a method for producing sintered ore that can increase the amount of pores in the sintered ore to improve the reducibility of the blast furnace raw material and suppress low-temperature reduction disintegration, and have found that the low-temperature reduction disintegration of sintered ore depends on the blending conditions of various raw materials in the sintering raw material before the sintering process.

[0032] In light of these considerations, in the present invention, in order to suppress the low-temperature reduction disintegration of sintered ore, it is preferable to adjust the blending ratio of the sintering raw material so that the CaO content of the sintered ore is 11.0 mass% or more. Specifically, it is preferable to increase the CaO content of the sintering raw material by adjusting the blending ratio of limestone or quicklime contained in the sintering raw material. This is because increasing the CaO content of the sintering raw material promotes the formation of calcium ferrite during the sintering process, which in turn suppresses the formation of hematite, which causes low-temperature reduction disintegration. Furthermore, if the CaO content of the sintered ore is excessively increased, the amount of slag produced in the blast furnace increases, resulting in a decrease in the energy efficiency of blast furnace operation. Therefore, it is preferable to adjust the CaO content of the sintering raw material so that the CaO content of the sintered ore is 12.0 mass% or less while suppressing low-temperature reduction disintegration.

[0033] Therefore, the average particle size of the iron ore (Marra Mamba ore) and other iron ores blended in the sintering raw materials is set to 2.0 mm or less, and the amount of coke fines blended in the sintering raw materials is set to less than 4.0 mass%. Furthermore, the blending ratio of the sintering raw materials is adjusted so that the CaO content of the sintered ore is 11.0 mass% or more. This allows for a porosity of 27% or more by volume, a JIS-RI (reducibility) of 70% or more, and an RDI (reducibility index) of less than 30%. In other words, sintered ore that achieves both good reducibility and suppressed low-temperature reduction disintegration can be obtained. Here, the RDI (reducibility index) defined in JIS M8720 may be used as the RDI. The RDI of sintered ore produced using pisolite ore is approximately 30%. Therefore, by adjusting the CaO content of the sintered ore to a predetermined value, it is possible to suppress low-temperature reduction disintegration compared to sintered ore produced using pisolite ore.

[0034] The method for producing sintered ore of the present invention may be carried out as follows. First, a few percent of moisture is added to iron ore powder, auxiliary materials containing CaO such as limestone, auxiliary materials containing SiO such as silica, and a carbonaceous material such as coke, and the mixture is mixed and granulated to obtain a pseudo-particled sintered raw material. Next, the pseudo-particled sintered raw material is loaded onto a fire grate to form a raw material layer, and the surface layer of the raw material layer is ignited. Then, while air is drawn downward, the combustion of the carbonaceous material progresses downward, and the sintered raw material is sintered by the combustion heat of the carbonaceous material to produce a sintered cake. The produced sintered cake is then crushed and sized, and particles of a predetermined size or larger are used as raw material for blast furnace ironmaking. [Example]

[0035] Examples carried out using the method for producing sintered ore of the present invention will be described below.

[0036] A few percent of water was added to a blend of raw materials containing various iron ore powders, auxiliary materials containing CaO such as limestone, auxiliary materials containing SiO2 such as silica, and carbonaceous materials such as coke. The blended raw materials were mixed and granulated to obtain pseudo-particled sinter raw materials. A sintering test was conducted on the pseudo-particled sinter raw materials using a cylindrical sintering test pot with a diameter of 300 mm. A 20 mm layer of sintered ore was packed as a bedding on the fire grate inside the cylindrical sintering test pot, and the pseudo-particled sinter raw materials were packed on top of that as a sinter raw material layer. The carbonaceous material contained above the packed sinter raw material layer was ignited, and air was drawn downward while the combustion of the carbonaceous material proceeded downward. The sintered raw material layer was sintered by the combustion heat of the carbonaceous material to obtain a sintered cake. Table 2 shows the raw material blend amounts, average particle size of all iron ores, total crystallization water blend amount, and target composition of the sintered ore (sintered ore composition) for each example. Table 3 also shows the sintering process conditions for each example. Here, the total amount of crystallization water means the amount of all crystallization water contained in all iron ores blended in the sintering raw material, in the sintering raw material blended with all the raw materials listed as the raw material blending amount.

[0037] [Table 2]

[0038] [Table 3]

[0039] The resulting sinter cake was then crushed by dropping it four times from a height of 2 m. Sintered ore sized 5 mm or larger was then collected and used to evaluate its reducibility, porosity, and low-temperature reduction disintegration. The reducibility of the sintered ore was evaluated by measuring the achieved JIS reduction ratio (RI) as specified in JIS M8713. The low-temperature reduction disintegration of the sintered ore was evaluated by measuring the reduction disintegration index (RDI) as specified in JIS M8720. The porosity of the sintered ore was evaluated by first measuring the apparent density using a submerged weighing method in water, and then crushing the sintered ore and sieving it through a 250 μm mesh sieve. The porosity of the sintered ore was then calculated from the pore volume per volume of the sintered ore based on the true density obtained. The evaluation results of the sintered ore are shown in Table 4.

[0040] [Table 4]

[0041] Comparative Examples 1 and 2 are examples in which sintered ore was produced by blending pisolite ore with the sintering raw material. Because pisolite ore was used in Comparative Examples 1 and 2, the porosity was 20% by volume or more and the reducibility was 65% or more, as shown in Table 4. Furthermore, because pisolite ore was used in Comparative Examples 1 and 2, the reduction degradation index (RDI) was approximately 30%.

[0042] Comparative Examples 3 and 4 are examples in which sintered ore was produced by blending Marra Mamba ore with the sintering raw material. Comparative Examples 3 and 4 had lower porosity and reducibility values ​​than Comparative Examples 1 and 2. Although Marra Mamba ore was used in Comparative Example 3, the total amount of crystallization water exceeded 3 mass%, resulting in a porosity of 20 volume% or more and a JIS-RI of 65% or more. In Comparative Example 4, the total amount of crystallization water was less than 3 mass% (see Table 2), resulting in a porosity of less than 20 volume% and a reducibility of less than 65%. In other words, it was confirmed that when Marra Mamba ore was blended and the total amount of crystallization water was small, the porosity decreased to less than 20% and the JIS-RI decreased to less than 65%.

[0043] In Example 1, sinter was produced by blending Marra Mamba ore with the sintering raw material, and further, when the total amount of crystallization water was less than 3.0% by mass, the average particle size of all iron ores blended in the sintering raw material was set to 2.0 mm or less. In Example 1, although the total amount of crystallization water was low at 2.3% by mass, the porosity was 20% by volume or more, and the reducibility was 65% or more. In other words, by blending Marra Mamba ore with the sintering raw material and setting the average particle size of all iron ores blended in the sintering raw material to 2.0 mm or less, a predetermined amount of pores was formed within the sintered ore, thereby achieving good reducibility. This is thought to be due to the fact that the amount of pores remaining in the sintered ore after agglomeration was increased by reducing the particle size of the iron ore.

[0044] In Example 2, Marra Mamba ore was blended into the sintering raw material, and the total amount of crystallization water was less than 3.0% by mass. Sinter was produced by setting the average particle size of all iron ores blended into the sintering raw material to 2.0 mm or less, and further setting the amount of coke fines blended into the sintering raw material to less than 4.0% by mass. In Example 2, the porosity was 27% by volume or more, and the reducibility was 70% or more. That is, Marra Mamba ore was blended into the sintering raw material, the average particle size of all iron ores blended into the sintering raw material to 2.0 mm or less, and further setting the amount of coke fines blended into the sintering raw material to less than 4.0% by mass. Therefore, it was confirmed that the porosity and reducibility of the sintered ore that underwent the sintering process could be improved. This is thought to be due to the fact that limiting the amount of coke fines to less than 4.0% by mass suppressed pore blockage by the melt.

[0045] In Example 3, Marra Mamba ore was blended into the sintering raw material, and when the total amount of crystallization water blended was less than 3.0% by mass, the average particle size of all iron ores blended into the sintering raw material was set to 2.0 mm or less, and the blending of the sintering raw material was adjusted so that the CaO content of the sintered ore was 11.0% by mass or more. In Example 3, the amount of limestone blended was increased compared to Examples 1 and 2 to ensure that the CaO content of the sintered ore was 11.0% by mass or more. In Example 3, as in Example 1, the porosity was approximately 20% by volume or more, and the reducibility was 65% or more. Furthermore, in Example 3, low-temperature reduction disintegration was suppressed compared to Example 1. Specifically, the low-temperature reduction disintegration was less than 30%, which was a better result than Comparative Examples 1 and 2, in which pisolite ore was used. Specifically, Marra Mamba ore was blended into the sintering raw material, the average particle size of all iron ores blended in the sintering raw material was set to 2.0 mm or less, and the blending of the sintering raw material was adjusted so that the CaO content of the sintered ore was 11.0 mass% or more. It was confirmed that by forming a predetermined amount of pores inside the sintered ore that had undergone the sintering process, good reducibility was achieved and the low-temperature reduction disintegration of the sintered ore could be suppressed.

[0046] In Example 4, Marra Mamba ore was blended into the sintering raw material, and when the total amount of crystallization water was less than 3.0% by mass, the average particle size of all iron ores blended into the sintering raw material was adjusted to 2.0 mm or less, and the amount of coke fines blended into the sintering raw material was adjusted to less than 4.0% by mass. Furthermore, the blending of the sintering raw material was adjusted so that the CaO content of the sintered ore was 11.0% by mass or more, and sintered ore was produced. In Example 4, the amount of limestone blended was increased compared to Examples 1 and 2 to ensure that the CaO content of the sintered ore was 11.0% by mass or more. In Example 4, similar to Example 2, the porosity was 27% by volume or more, and the reducibility was 70% or more. Furthermore, in Example 4, low-temperature reduction disintegration was suppressed compared to Example 2. Specifically, the low-temperature reduction disintegration was less than 30%, which was a better result than Comparative Examples 1 and 2, which used pisolite ore. That is, Marra Mamba ore was blended into the sintering raw material, and the blending of the sintering raw material was adjusted so that the average particle size of all the iron ores blended in the sintering raw material was 2.0 mm or less, the blending amount of coke fines was less than 4.0 mass%, and the CaO content of the sintered ore was 11.0 mass% or more. It was confirmed that the porosity and reducibility of the sintered ore that underwent the sintering process could be improved, and that the low-temperature reduction disintegration of the sintered ore could be suppressed.

Claims

1. Iron content is 58.00 mass% or more, crystal water content is 4.00 mass% or more but less than 9.00 mass%, Al ２ O ３ The content is 2.00 mass% or more, SiO ２ A method for producing sintered ore from sinter raw materials in which 15.0% by mass or more of iron ore having a content of less than 5.00% by mass is blended, and the total amount of water of crystallization contained in all the blended iron ores is 0.0% by mass or more but less than 3.0% by mass, A method for producing sintered ore, wherein the average particle size calculated as an arithmetic mean diameter of all the iron ore particles blended in the sintering raw material is 2.0 mm or less.

2. The method for producing sintered ore according to claim 1, wherein the amount of coke fines mixed in the sintering raw material is less than 4.0 mass%.

3. The method for producing sintered ore according to claim 1 or 2, wherein the blending of the sintering raw materials is adjusted so that the CaO content of the sintered ore is 11.0 mass % or more.

Images