Sintered ore and method for producing same, and sintered ore for hydrogen reduction and method for producing same

Abstract

Provided are: a sintered ore having both improved reducibility and low reduction degradation properties; and a method for producing the sintered ore. Also provided are: sintered ore for hydrogen reduction; and a method for producing the sintered ore. A sintered ore having a ratio PA / PB of 0.23 or more, the ratio PA / PB being the ratio of the porosity PA (vol%) of sintered ore having a particle diameter of 5 mm or more as measured by mercury intrusion after crushing the sintered ore such that the average particle diameter is in the range of 1-2 mm, and the porosity PB being calculated using the apparent density and true density for the sintered ore. The apparent density is determined by using water through a liquid weighing method, and the true density is determined by crushing the sintered ore, screening the crushed sintered ore until the particle size is 250 microns and then determining the screened sintered ore through a boiling method or a vacuum suction method. A method for producing sintered ore uses a raw material containing ore having a crystal water content of 4% by mass or more. And a sintered ore for hydrogen reduction having a porosity ratio (PA / PB) of 0.25 or more.

Description

Technical Field

[0001] The present invention relates to a sintered ore having an excellent balance between reducibility and reduction pulverization property and a method for producing the same, and a sintered ore for hydrogen reduction and a method for producing the same. Background Art

[0002] As one of the iron-making methods for reducing iron from a raw material containing iron oxide, the direct reduction iron-making method is known. The direct reduction iron-making method has been continuously developed on the basis that the equipment used to carry out the method is inexpensive to build, easy to operate, and can be operated even on a small scale. In particular, various improvements have been made in the vertical furnace direct reduction furnace in order to effectively utilize the reducing gas in the furnace.

[0003] For the direct reduction furnace using the vertical furnace method to perform stable operation, the improvement of reducibility and low reduction pulverization brought about by ensuring stable ventilation of the reducing gas and ensuring the logistics of the iron oxide raw material have become important technical issues. In the high-temperature area at the bottom of the vertical furnace, when the iron oxide raw material is reduced and pulverized, the ventilation resistance increases, which not only reduces the productivity in the vertical vertical furnace, but also causes the iron oxide raw material to descend poorly, leading to production obstacles. The increase in ventilation resistance and reduction in productivity when the iron oxide raw material is reduced and pulverized also occur in the blast furnace method. However, unlike the blast furnace method, in the direct reduction ironmaking method in which the iron oxide raw material is directly reduced and discharged in a solid state, if reduction pulverization occurs during the process in which the iron oxide raw material is directly reduced in a solid particle state, the particles will fuse with each other (called clusters), hindering the discharge from the reduction furnace. Therefore, compared with the blast furnace method, the direct reduction ironmaking method needs to suppress the reduction pulverization of the iron oxide raw material more.

[0004] Regarding the improvement of reducibility, for example, Patent Document 1 discloses that the pores remaining in the sintered ore have a pore diameter of 2 to 5 mm, with pores above that being open and pores below that being closed. In particular, closed pores with a pore diameter of 0.5 mm or less dominate reducibility.

[0005] In addition, Non-Patent Document 1 reports that the proportion and structure of large pores that supply reducing gas to each structure play an important role in determining the reducibility of the sintered ore as a whole. In Non-Patent Document 1, large pores are defined as nearly spherical pores with a pore diameter greater than about 50 μm.

[0006] For such reasons, reports on pore structure analysis have increased, and as in Non-Patent Documents 2 and 3, models for predicting porosity and models for predicting reduction rates have been reported.

[0007] Patent document 2 discloses a sintered ore with high reducing property, wherein, as a preparation index of sintered ore for blast furnace, an organic binder containing 3 mass % or more of H is added and granulated to thereby have a structure having a fine porosity ratio of 0.42 or more with a pore diameter of 100 μm or less.

[0008] In addition, regarding the quality during hydrogen reduction, Patent Document 3 discloses that when a raw material for direct reduction such as pellets is reduced using a vertical furnace, reduction pulverization can be suppressed by constructing a raw material and a coating layer covering the raw material and having a porous structure with a porosity of 20% by volume or more.

[0009] Prior art literature

[0010] Patent Literature

[0011] Patent Document 1: Japanese Patent Application Laid-Open No. 10-324929

[0012] Patent Document 2: Japanese Patent Application Publication No. 2017-75348

[0013] Patent Document 3: International Publication No. 2015 / 016145

[0014] Non-patent literature

[0015] Non-patent document 1: Maeda Noriyuki, Ono Yoichi: Iron and Steel, 72 (1986) 7, pp775-782

[0016] Non-patent document 2: Kawaguchi Takazo, Sato Shun, Takada Kozo: Iron and Steel, 73 (1987) 15, pp1940-1947

[0017] Non-patent document 3: Sato Shun, Kawaguchi Takazo, Ichiida Minoru, Yoshinaga Mayumi: Iron and Steel, 73 (1987) 7, pp804-811 Summary of the invention

[0018] Problems to be solved by the invention

[0019] It can be seen from the above-mentioned prior art that the pore structure affects the reducibility and the reduction pulverization property, and its control is important.

[0020] However, it is generally known that improvement in reducing property and low reducing powdering property are in a conflicting relationship, and therefore, if reducing powdering is suppressed, reducing property deteriorates.

[0021] That is, in order to take into account both the improvement of reducibility and the low reduction pulverization, it is necessary to control the porosity and pore structure from large to small. However, in the above-mentioned prior art, only a certain range of porosity is focused on, and no such attempt is made. It becomes a problem to propose a pore structure that can take into account both the improvement of reducibility and the low reduction pulverization.

[0022] An object of the present invention is to provide a sintered ore or a sintered ore for hydrogen reduction, and a method for producing the sintered ore or the sintered ore for hydrogen reduction, wherein the sintered ore or the sintered ore for hydrogen reduction is used in a blast furnace process or direct reduction and has both improved reducibility and low reduction pulverization.

[0023] Means for solving problems

[0024] The inventors have understood the pore structures that contribute to the reducibility and the reduction-powdering properties, respectively, and have attempted to construct a concept related to new pores that can achieve both.

[0025] The sintered ore according to the present invention, which advantageously solves the above-mentioned problems, is characterized in that the porosity P A (Volume %) and porosity P B (volume %) ratio P A / P B is 0.23 or more, the porosity P A The porosity P is measured by the mercury intrusion method after the sintered ore having a particle size of 5 mm or more is crushed so that the average particle size is in the range of 1 to 2 mm. B The apparent density is determined by weighing the sintered ore in a liquid using water, and the true density is determined by boiling or vacuuming the sintered ore after the sintered ore is crushed and sieved to a particle size of -250 μm.

[0026] In addition, for the sintered ore according to the present invention, the following means are considered to be more preferable solutions.

[0027] (a) The porosity P A The range is 3 to 13% by volume,

[0028] (b) The porosity P B In the range of 10 to 42% by volume,

[0029] (c) The average pore diameter d measured by the above mercury intrusion method A 0.7μm or less,

[0030] etc.

[0031] The sintered ore for hydrogen reduction according to the present invention, which advantageously solves the above-mentioned problems, is characterized in that, in any of the above-mentioned sintered ore, the porosity ratio P A / P B It is 0.25 or more.

[0032] The method for producing sintered ore according to the present invention, which advantageously solves the above-mentioned problems, is characterized in that, in any of the above-mentioned methods for producing sintered ore, a raw material containing an ore having a crystal water content of 4% by mass or more is used. For the method for producing sintered ore according to the present invention, it is considered that the following means can be a more preferred solution, that is, including blowing a gas fuel as a sintering fuel, and the gas fuel is a combustible gas selected from any one of hydrogen, blast furnace gas, coke oven gas, blast furnace and coke oven mixed gas, town gas, natural gas, methane gas, ethane gas, propane gas, butane gas, and a mixed gas thereof.

[0033] The method for producing a sintered ore for hydrogen reduction according to the present invention, which advantageously solves the above-mentioned problems, is characterized in that, in any of the above-mentioned methods for producing a sintered ore, the porosity ratio P of the sintered ore is set to A / P B It is 0.25 or more.

[0034] Effects of the Invention

[0035] According to the sintered ore and the sintered ore for hydrogen reduction of the present invention, the pore structure can be controlled to obtain a sintered ore and a sintered ore for hydrogen reduction that have both improved reducibility and low reduction pulverization, and thus are suitable as raw materials for direct reduction ironmaking using a blast furnace method, a shaft furnace, etc. In addition, according to the method for producing a sintered ore and the method for producing a sintered ore for hydrogen reduction of the present invention, the pore structure of the sintered ore can be appropriately controlled. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] [ Figure 1 ] is a flow chart showing a method for measuring the porosity of a sintered ore according to one embodiment of the present invention.

[0037] [ Figure 2 ] is a graph showing the relationship between the JIS reduction ratio (JIS-RI) and the reduction pulverization index (JIS-RDI) of sintered ore.

[0038] [ Figure 3 ] is the micro porosity P A A graph showing the relationship with the JIS reduction ratio (JIS-RI).

[0039] [ Figure 4 ] is the micro porosity P A A graph showing the relationship with the reduced powdering index (JIS-RDI).

[0040] [ Figure 5 ] is the ratio of microporosity to macroporosity P A / P B A graph showing the influence of JIS reduction rate and reduction powdering index ratio JIS-RI / JIS-RDI.

[0041] [ Figure 6 ] is the ratio of microporosity to macroporosity P A / P B This is a graph showing the influence of the average pore diameter of sintered ore measured by mercury intrusion porosimetry on the ratio of JIS reduction rate to reduction powdering index JIS-RI / JIS-RDI of 0.25 or more. DETAILED DESCRIPTION

[0042] Hereinafter, the embodiments of the present invention will be described in detail with reference to the accompanying drawings. The following embodiments illustrate methods for implementing the technical concept of the present invention, and the configuration thereof is not limited to the following configuration. That is, the technical concept of the present invention can be subjected to various changes within the technical scope described in the claims.

[0043] The inventors measured and quantified the micropores with a pore diameter of 200 μm or less that affect the reducibility of sintered ore and the large pores that affect the strength of sintered ore. Then, they studied the preferred characteristics of sintered ore, especially sintered ore for hydrogen reduction. The flow of the evaluation method is shown in Figure 1 .

[0044] The sintered ore S0, which is the object of porosity measurement, uses a particle size of +5mm as the finished sintered ore. Here, the particle size of +5mm represents the oversize obtained by screening with a sieve with a mesh opening of 5mm. In addition, for example, the particle size of -5mm represents the undersize obtained by screening with a sieve with a mesh opening of 5mm. First, the sintered ore S0 is screened as needed, for example, so that the particle size is consistent with about 19 to 21mm (S1). As long as it is a finished sintered ore with a particle size of +5mm, it does not matter what the particle size is, and there is no problem even if it is used without screening. By making the particle size consistent to a certain extent, the subsequent crushing load can be reduced.

[0045] The porosity P of the micropores of the obtained sintered ore S1 with uniform particle size was determined as follows: A and pore diameter d A .

[0046] (S11) The sintered ore S1 is crushed and sieved into a particle size of +1 mm to 2 mm. As a crushing method, it is preferable to use a crushing device such as a disc mill or a jaw crusher, which prevents the crushed material from being further crushed after being crushed to a particle size below a predetermined size.

[0047] (S12) According to JIS R 1655:2003, the pore diameter distribution of the obtained sintered ore with a particle size of +1 mm to 2 mm is measured by mercury intrusion, and the porosity P is calculated from the cumulative pore volume of pores with a diameter of 3.6 nm to 200 μm. A (S13) and average pore diameter d A(S14) Here, the pore diameter refers to the cylindrical diameter calculated by the Washburn formula of the following formula (1) assuming that the open pore is cylindrical. In addition, the average pore diameter d A It is the 50% value of the cumulative volume basis.

[0048] d=-4σ(cosθ) / P (1)

[0049] Here, d represents the pore diameter (m), σ represents the surface tension of mercury (N / m), θ represents the contact angle between the measurement sample and mercury (°), and P represents the pressure applied to mercury (Pa).

[0050] In addition, the porosity P of the large pores of the sintered ore S1 obtained by uniforming the particle size is B The determination was performed as follows.

[0051] (S21) The apparent density of the sintered ore S1 was measured by the liquid weighing method using the Archimedean principle in accordance with JIS Z8807: 2012. First, the sintered ore S1 was weighed in a dry state.

[0052] (S22) Next, the same sintered ore S1 is weighed in water. The apparent density of the sintered ore S1 is determined by the submerged weighing method based on the density of water as a standard substance at the measurement temperature.

[0053] (S23) The sintered ore S1 is pulverized, and the true density of the sieve-undersized material having a particle size of -250 μm is measured by a boiling method or a vacuum suction method in accordance with JIS R1634:1998.

[0054] (S24) Compare the apparent density of the sintered ore S1 with the true density after crushing, and calculate the porosity P of the large pores. B .

[0055] (Example)

[0056] Sintered ores produced under various operating conditions were collected from the sampler of the actual sintering machine by mixing various raw materials within the range of the component composition in Table 1. The reduction rate JIS-RI (mass %) was measured in accordance with JIS M8713:2009 for the reducibility of the sintered ores. In addition, the reduction pulverization index JIS-RDI (mass %) was measured in accordance with JIS M8720:2017 for the reduction pulverization of the sintered ores. Figure 2The relationship between the reducibility and reduction pulverization of sintered ores manufactured with various mix ratios and various operating conditions is shown in a graph. The reducibility is represented by the reduction rate JIS-RI on the horizontal axis, and the reduction pulverization is represented by the reduction pulverization index JIS-RDI on the vertical axis. As long as it is a normal mix ratio and operating conditions, a positive correlation is obtained as depicted by the hollow circle (○). The higher the reduction rate JIS-RI and the lower the reduction pulverization index JIS-RDI, the better. If this situation is taken into account, it can be seen that the reducibility and reduction pulverization are usually opposite and difficult to meet at the same time. In a part, the depiction of the solid circle (●) obtained a sintered ores with excellent reducibility and reduction pulverization, so the relationship with the porosity was investigated.

[0057] [Table 1]

[0058]

[0059] exist Figure 3 and Figure 4 The porosity P of the micropores is shown in the graphs. A Relationship with reduction rate JIS-RI and reduction powdering index JIS-RDI. Porosity P of micropores A As is known in the past, the reduction rate JIS-RI has a positive correlation. A No clear correlation was found between the reduction pulverization index JIS-RDI. Therefore, it is difficult to obtain a sintered ore excellent in both reducibility and reduction pulverization by simply controlling the porosity of micropores.

[0060] As appropriate operating conditions, the ratio of reduction rate to reduction pulverization index (JIS-RI / JIS-RDI) was analyzed for conditions that can obtain sintered ore with a reduction rate JIS-RI of 70% by mass or more. The larger the value, the more likely it is to obtain conditions that take both reduction and reduction pulverization into account.

[0061] It was found that if the porosity ratio of micropores to macropores (P A / P B ) for finishing, the conditions that take into account both appropriate reducibility and reductive powdering properties can be obtained. Figure 5 The ratio of microporosity to macroporosity is shown in the graph A / P B The influence of JIS reduction rate and reduction powder index ratio JIS-RI / JIS-RDI. It can be seen that by making the porosity ratio P A / P B 0.23 or more, a sintered ore having a JIS-RI / JIS-RDI of 2.0 or more and excellent reducibility and reduction pulverization properties can be obtained. A / PB The porosity ratio P is 0.25 or more, and JIS-RI / JIS-RDI can be 2.5 or more, which is preferable as a sintered ore for hydrogen reduction. A / P B The upper limit of is not particularly limited, but is preferably based on the microporosity P described below. A , atmospheric porosity P B Set an upper limit for the appropriate range.

[0062] Depend on Figure 3 It can be seen that if the porosity P of the micropores A If the reduction ratio is less than 3% by volume, it is difficult to make the reduction ratio JIS-RI 70% by mass or more. A If the porosity exceeds 13% by volume, the micropores will be close to each other, and the strength of the sintered ore may be reduced. A The range of 3 to 13 volume % is preferable.

[0063] In addition, the porosity P of the large pores is B It is difficult to sinter ore with a content of less than 10 vol%. B For sintered ore with a content of more than 42% by mass, the reduction rate JIS-RI is too low or the reduction powder index JIS-RDI is too high, and the balance becomes poor. B The content is preferably in the range of 10 to 42% by volume.

[0064] For sintered ore with excellent balance between reducibility and reduction pulverization, the ratio of JIS reduction rate to reduction pulverization index JIS-RI / JIS-RDI is the average pore diameter d of the relative micropores. A The relationship is shown in Figure 6 By making the average pore diameter d A When the average pore diameter is 0.7 μm or less, the strength of the sintered ore is increased, and a sintered ore having a better balance between reducibility and reduction pulverization can be obtained. A The lower limit of is not particularly limited, but considering the above-mentioned appropriate range of microporosity, it is preferably about 0.1 μm.

[0065] Conventional methods can be used to produce sintered ore. If ore containing 4% or more of crystal water is added and the crystal water is evaporated during the sintering process, fine pores can be generated in the sintered ore, which can increase the microporosity P. A , so it is preferred.

[0066] Furthermore, by injecting gaseous fuel as sintering fuel, the amount of melt can be increased during the sintering process, and the porosity P can be reduced. BHere, the gas fuel is preferably a combustible gas selected from any one of hydrogen, blast furnace gas, coke oven gas, blast furnace and coke oven mixed gas, town gas, natural gas, methane gas, ethane gas, propane gas, butane gas and their mixed gases.

[0067] Industrial Applicability

[0068] The sintered ore and its manufacturing method, and the sintered ore for hydrogen reduction and its manufacturing method according to the present invention can improve the reducibility and reduction pulverization property in a balanced manner by appropriately controlling the ratio of micropores to macropores. The obtained sintered ore is used for blast furnace applications to help stabilize the operation, and can be used as an iron source for suppressing the emission of carbon dioxide gas, especially for hydrogen reduction applications, so it is useful in industry from the viewpoint of reducing the environmental load.

Claims

1. Sintered ore, its porosity P A (Volume %) and porosity P B (volume %) ratio P A / P B is 0.23 or more, The porosity P A The sintered ore with a particle size of 5 mm or more is crushed to an average particle size of 1 to 2 mm and then measured by mercury intrusion porosimetry. The porosity P B The apparent density is determined by weighing the sintered ore in a liquid using water, and the true density is determined by boiling or vacuuming the sintered ore after the sintered ore is crushed and sieved to a particle size of -250 μm.

2. The sintered ore according to claim 1, wherein: The porosity P A The range is 3 to 13% by volume.

3. The sintered ore according to claim 1 or 2, wherein: The porosity P B The range is 10 to 42% by volume.

4. The sintered ore according to any one of claims 1 to 3, wherein The average pore diameter d measured by the mercury intrusion method is A It is less than 0.7μm.

5. Sintered ore for hydrogen reduction, wherein: In the sintered ore according to any one of claims 1 to 4, the porosity ratio P A / P B It is 0.25 or more.

6. A method for producing a sintered ore, the method being a method for producing the sintered ore according to any one of claims 1 to 4, wherein: A raw material containing ore having a crystal water content of 4 mass % or more is used.

7. The method for producing sintered ore according to claim 6, comprising injecting a gaseous fuel as a sintering fuel.

8. The method for producing sintered ore according to claim 7, wherein: The gas fuel is a combustible gas selected from any one of hydrogen, blast furnace gas, coke oven gas, blast furnace and coke oven mixed gas, town gas, natural gas, methane gas, ethane gas, propane gas, butane gas and mixed gases thereof.

9. A method for producing sintered ore for hydrogen reduction, wherein: In the method for producing a sintered ore according to any one of claims 6 to 8, the porosity ratio P of the sintered ore is A / P B It is 0.25 or more.

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