Method for crushing ore and method for manufacturing pellet

Abstract

Provided is a method for pulverizing an iron ore that is difficult to be finely pulverized with high efficiency. The method for pulverizing an iron ore, which is a method for coarsely pulverizing the aforementioned iron ore to reduce the proportion of particles having a particle size of 1 mm or more and finely pulverizing the aforementioned iron ore to increase the proportion of particles having a particle size of less than 63 μm. Furthermore, it is preferable that the aforementioned iron ore have an average pore diameter of 10 μm or less; the proportion of particles having a particle size of 1 mm or more be 30% by mass or more, so that the proportion of particles having a particle size of 1 mm or more of the aforementioned iron ore becomes 20% by mass or less; the aforementioned iron ore be finely pulverized so that the proportion of particles having a particle size of less than 63 μm becomes 70% by mass or more; and the fine pulverization be performed using a wet-type ball mill. A method for manufacturing a pellet, which pellets are manufactured by granulating a raw material containing the iron ore that is pulverized using the method for pulverizing an iron ore.

Description

Technical Field

[0001] This invention relates to a method for crushing ore, and to a method for manufacturing pellets using iron ore processed by the crushing method as raw material. Background Technology

[0002] When iron ore is used in the ironmaking process, sinter and pellets (neither sintered nor calcined) are produced through a granulation process. For improvements in the granulation operation to increase the yield and productivity of sinter and pellets, ore crushing is known to be effective.

[0003] For example, Patent Document 1 discloses a technique for using pre-crushed micro-powdered ore as a granulation raw material when manufacturing sintered ore.

[0004] Furthermore, Patent Document 2 discloses a method for pulverizing iron ore raw materials using a roller mill. In this method, a second iron ore raw material with a higher hardness than the first iron ore raw material is mixed with a first iron ore raw material as a pulverizing aid. The mixed first and second iron ore raw materials are then fed into the roller mill for pulverization. The pulverized iron ore is then granulated to form sintering raw material pellets.

[0005] In addition, Patent Documents 3 and 4 disclose a method for manufacturing sintered ore by crushing iron ore and other materials that pass through a sieve with a specified sieve aperture, mixing them with iron ore and other materials that pass through the sieve, and then granulating them, in order to granulate iron ore containing a large amount of water of crystallization; and a method for pre-treating sintered raw materials by compressing and crushing them with a roller press and then granulating them.

[0006] In addition, Patent Document 5 discloses a method for manufacturing sintered ore by crushing porous iron ore before granulation.

[0007] Existing technical documents

[0008] Patent documents

[0009] Patent Document 1: Japanese Patent Application Publication No. 2016-17211

[0010] Patent Document 2: International Publication No. 2010 / 113571

[0011] Patent Document 3: Japanese Patent Application Publication No. 2008-261016

[0012] Patent Document 4: Japanese Patent Application Publication No. 2007-162127

[0013] Patent Document 5: Japanese Patent Application Publication No. 2007-138244 Summary of the Invention

[0014] The problem that the invention aims to solve

[0015] However, the aforementioned prior art has the following problems.

[0016] In other words, there is a problem that the technology for pulverizing iron ore containing coarse particles that are difficult to grind into fine powder is insufficient. Patent Document 1 only describes pulverization and does not mention countermeasures when poorly pulverizable ore is mixed in. Furthermore, the technology in Patent Document 2 is not a technology for pulverizing high-hardness iron ore raw materials used as pulverizing aids.

[0017] The technologies described in patent documents 3 and 4 are not technologies for solving the problem of mixed-in ores that are difficult to crush.

[0018] The technology described in Patent Document 5 is a technology for solving the problem of needing a large amount of water during the granulation process of porous raw materials, not a technology for solving the problem of mixed in ores that are difficult to crush.

[0019] The object of this invention is to provide a pulverizing method for iron ore that is difficult to micronize. Furthermore, the object of this invention is to provide a method for manufacturing pellets using iron ore processed by this pulverizing method as raw material.

[0020] Methods for solving problems

[0021] The inventors of this application have discovered that by pre-crushing iron ore into coarse powder, iron ore can be efficiently micro-crushed.

[0022] The ore crushing method of the present invention, which advantageously solves the above-mentioned problems, is a crushing method for ore containing iron ore. It is characterized in that, after coarsely crushing the iron ore to reduce the proportion of particles with a diameter of 1 mm or more, the coarsely crushed iron ore is then micro-crushed to increase the proportion of particles with a diameter of less than 63 μm.

[0023] Furthermore, the following aspects of the ore crushing method involved in this invention are considered to be a more preferred solution:

[0024] (a) The average pore size of the aforementioned iron ore before coarse crushing is less than 10 μm;

[0025] (b) The iron ore is coarsely crushed such that the proportion of the aforementioned iron ore with a particle size of 1 mm or more is 30% or more by mass, and the proportion of the aforementioned iron ore with a particle size of 1 mm or more is reduced to 20% or less by mass.

[0026] (c) The aforementioned iron ore is micronized in such a manner that the proportion of particles smaller than 63 μm is 70% or more by mass;

[0027] (d) Fine grinding using a wet ball mill;

[0028] etc.

[0029] The present invention, which advantageously solves the above-mentioned problems, is characterized in that a raw material comprising iron ore pulverized by any of the above-mentioned ore pulverization methods is granulated and pelletized.

[0030] Invention Effects

[0031] According to the present invention, even in the case of iron ore that is difficult to micronize, micronization can be carried out efficiently by pre-coarse crushing, and therefore it is preferred for use as raw material for sintering ore and for the manufacture of pellets. Attached Figure Description

[0032] [ Figure 1 [Illustration] is a schematic diagram showing the structure of a preferred ball mill used in micronization according to an embodiment of the present invention. Detailed Implementation

[0033] The embodiments of the present invention will now be described in detail. It should be noted that the accompanying drawings are schematic and may sometimes differ from reality. Furthermore, the following embodiments illustrate apparatus and methods for embodying the technical concept of the present invention, and the configuration is not limited to the described configuration. That is, various modifications can be made to the technical concept of the present invention within the scope of the claims.

[0034] Figure 1 A schematic diagram of a preferred ball mill used in micronization according to one embodiment of the present invention is shown. The ball mill 10 consists of approximately spherical balls 2 (a hard material such as alumina), a process material 3 (to be pulverized), and a liquid composition as needed, fed into a generally cylindrical rotating container 1. The balls roll as the rotating container 1 rotates, thereby micronizing the process material 3 between the balls 2 and between the balls 2 and the rotating container 1. For example, a rotating container 1 with a cylinder diameter of 0.67 m, a cylinder length of 0.5 m, a rotational power of 3.7 kW, a ball 2 made of alumina with a diameter of 20-25 mm, a ball filling weight of 140 kg, and a rotational speed of approximately 40 revolutions per minute can be used. It should be noted that, in addition to the ball mill described above, bead mills, air jet mills, roller mills, etc., can also be used as the pulverizer 10. In this embodiment, micronization is primarily a grinding process that increases the proportion of iron ore particles with a diameter of -63μm; it is a grinding process that increases the proportion of iron ore particles with a diameter of -63μm compared to the decrease in the proportion of particles with a diameter of +1mm. It should be noted that in this embodiment, a particle diameter of -63μm refers to the material passing through a sieve with a mesh size of 63μm, also described as particles with a diameter less than 63μm. On the other hand, a particle diameter of +1mm refers to the material passing through a sieve with a mesh size of 1mm, also described as particles with a diameter of 1mm or larger.

[0035] For the granulation properties of iron ore, a higher proportion of -63 μm particles resulted in better granulation. The three types of iron ore listed in Table 1 were micro-milled for 30 minutes using the ball mill described above. The proportion of -63 μm particles was then evaluated by sieving. The results are shown in Table 1 below. As shown in Table 1, despite micro-milling for the same duration, the average pore size d... A Smaller iron ore particles have a lower proportion of particles with a diameter of -63 μm. This result indicates that the average pore size d... A For iron ores with a diameter of less than 10 μm, OreB and OreC are related to the average pore size d. A Compared to OreA iron ore with a diameter greater than 10 μm, this type of iron ore has poor micronization properties and is difficult to micronize. Here, the average pore size d... A According to JIS R1655:2003, the pore size distribution was determined by mercury porosimetry, and the cumulative pore volume of pore sizes from 3.6 nm to 200 μm was used as 50% of the value. Here, pore size refers to the diameter of the cylinder calculated using the Washburn formula in equation (1) assuming the pores are cylindrical.

[0036] d=-4σ(cosθ) / P (1)

[0037] Here, in equation (1) above, d represents the pore size (m), σ represents the surface tension of mercury (N / m), θ represents the contact angle between the sample and mercury (°), and P represents the pressure applied to the mercury (Pa). For example, an AutoPore IV9520 (manufactured by Micromeritics) can be used as the measuring device, with a surface tension of mercury of 0.48 N / m and a contact angle between mercury and sample of 140°.

[0038] [Table 1]

[0039]

[0040] Next, for the average pore size d with poor micronization... A For iron ore OreB and d with a diameter of less than 10 μm A For OreA iron ore with a particle size greater than 10 μm, the ore was first coarsely crushed using a jaw crusher, and the particle size ±1 mm ratio was measured. Then, the coarsely crushed iron ore was used in a dry state. Figure 1The ball mill shown was used for 30 minutes of micro-grinding. The proportion of iron ore with a particle size of -63 μm in the micro-grinded iron ore was measured. Then, 2% by mass of slaked lime was added to the micro-grinded iron ore and mixed, and then granulated using a granulator with a moisture content of 7% by mass. The crushing strength of the granulated pellets was measured using Autogrip at a speed of 1 mm / min. The crushing strength was taken as the average of 10 values. From the viewpoint of suppressing pulverization during transport, the crushing strength of the granulated pellets is generally preferred to be 49 N or higher. The test conditions and the results of the crushing strength measurement are shown in Tables 2 and 3 below. In this embodiment, coarse grinding is mainly a grinding process that reduces the proportion of iron ore with a particle size of +1 mm, and a grinding process that reduces the proportion of iron ore with a particle size of +1 mm compared to the increase in the proportion of iron ore with a particle size of -63 μm.

[0041] [Table 2]

[0042]

[0043] Table 2 shows the results for OreB iron ore. As shown in Table 2, the more the poorly pulverizable OreB iron ore is pre-crushed to reduce the proportion of particles with a diameter of +1 mm, the more the proportion of particles with a diameter of -63 μm after 30 minutes of fine pulverization increases. This result indicates that when the average pore size d... A In the case of micro-pulverizing iron ore with a particle size of less than 10 μm, by pre-coarsely pulverizing to reduce the proportion of particles larger than 1 mm, it is possible to efficiently carry out micro-pulverization that increases the proportion of particles with a particle size of -63 μm.

[0044] Furthermore, it takes approximately 10 seconds to coarsely crush OreB iron ore with a particle size of +1 mm (42.7% by mass) to a particle size of +1 mm (18.9% by mass) using a jaw crusher. On the other hand, it takes approximately an additional 30 minutes to finely crush OreB iron ore with a particle size of -63 μm (60.7% by mass) to a particle size of -63 μm (73.3% by mass) using a ball mill.

[0045] Therefore, it can be seen that by pre-crushing 42.7% by mass of iron ore with a particle size of +1 mm of 30% or more, and reducing the particle size of +1 mm to 18.9% by mass of 20% or less, it is possible to achieve a particle size of -63 μm of 70% or more in a short time. Furthermore, by granulating iron ore with a particle size of -63 μm of 70% or more into pellets, it is possible to produce pellets with a crushing strength of 49 N or more that can suppress pulverization during transport.

[0046] [Table 3]

[0047]

[0048] Table 3 shows the results for OreA iron ore. As shown in Table 3, in the case of OreA iron ore, the more the proportion of +1mm particles is reduced by pre-coarse grinding, the more the proportion of -63μm particles increases after 30 minutes of fine grinding. Furthermore, the time required to coarsely grind OreA iron ore with a +1mm particle size of 37.2% by mass to 13.3% by mass is achieved using a jaw crusher is approximately 10 seconds. On the other hand, to finely grind OreA iron ore with a -63μm particle size of 71.6% by mass to 82.8% by mass is achieved using a ball mill, an additional 12 minutes is required. Thus, with an average pore size d... A Coarse grinding followed by fine grinding of iron ore (OreA) with a diameter greater than 10 μm can reduce the grinding time by approximately 12 minutes. In contrast, with an average pore size d... A For OreB iron ore with a particle size of less than 10 μm, a time reduction of approximately 30 minutes can be achieved. These results indicate that the ore crushing method described in this embodiment is more preferably applied to ore with an average pore size d. A Iron ore with a particle size of less than 10 μm.

[0049] It should be noted that the ore pulverization method described in this embodiment can also be applied to iron ore where it is uncertain whether the iron ore contains iron ore that is difficult to pulverize. Therefore, even if the iron ore contains iron ore that is difficult to pulverize, pulverization can be carried out efficiently to increase the proportion of iron ore with a particle size of -63μm.

[0050] (First Embodiment)

[0051] Based on the aforementioned research, the inventors of this application have discovered a first embodiment for improving the crushing efficiency of iron ore. Specifically, the iron ore is pre-crushed using a crushing device such as a roller press or jaw crusher to reduce the proportion of particles with a diameter greater than 1 mm, and then finely crushed using a crushing device such as a ball mill to increase the proportion of particles with a diameter less than 63 μm. In this way, by pre-crushing the iron ore, even if the iron ore contains particles that are difficult to finely crush, it can be efficiently finely crushed. It should be noted that the iron ore may also contain other ores. In this case, as long as they are all coarsely crushed together to reduce the proportion of iron ore particles with a diameter greater than 1 mm, then fine crushing can be performed.

[0052] (Second Implementation)

[0053] In the second embodiment, the average pore diameter d was found to be... A This is related to the fineness of iron ore. Specifically, it relates to the average pore size d.A Iron ore with a diameter greater than 10 μm exhibits good micronization properties and can therefore be directly fed into grinding devices such as ball mills. On the other hand, the average pore size d... A Since iron ore with a particle size of less than 10 μm has poor micro-grindability, it is preferable to pre-crush it to reduce the proportion of particles with a diameter of +1 mm before feeding it into a grinding device such as a ball mill, where micro-grinding is also performed. In this way, by identifying iron ore with poor micro-grindability and pre-crushing it, the amount of iron ore that needs to be pre-crushed can be reduced, and the iron ore can be ground more efficiently.

[0054] (Third Implementation)

[0055] The inventors of this application have discovered a third embodiment for improving the crushing efficiency of iron ore with a particle size of 1 mm or more accounting for 30% or more by mass, based on the above-mentioned research. Specifically, iron ore with a particle size of 1 mm or more accounting for 30% or more by mass is coarsely crushed using a crushing device such as a roller press or jaw crusher to reduce the proportion of iron ore with a particle size of 1 mm or more to 20% or less by mass, and then finely crushed using a crushing device such as a ball mill. In this way, by pre-crushing the iron ore coarsely, it is possible to efficiently finely crush the iron ore. It should be noted that the proportion of particle size + 1 mm after coarse crushing is preferably 10% or less by mass. The lower limit of the proportion of particle size + 1 mm is not particularly limited and can also be 0. Furthermore, the iron ore may contain other ores; as long as these are coarsely crushed together to reduce the proportion of iron ore with a particle size of 1 mm or more to 20% or less by mass, and then finely crushed, it is acceptable.

[0056] (Fourth implementation)

[0057] The fourth embodiment is based on insights gained from granulating crushed iron ore into pellets. Specifically, in the micro-grinding process of iron ore, the ore is micro-grinded such that the proportion of particles with a diameter of -63 μm is 70% by mass or more. This improves the crushing strength of the granulated pellets and suppresses pulverization during pellet transport. Preferably, the micro-grinding is performed such that the proportion of particles with a diameter of -63 μm is 80% by mass or more. While there is no particular upper limit to the proportion of particles with a diameter of -63 μm, it is set to approximately 98% by mass, taking into account the grinding load.

[0058] (Fifth Embodiment)

[0059] The fifth embodiment was developed from the viewpoint of preventing dust during micro-grinding. Specifically, a wet ball mill was used as the micro-grinding device. Iron ore that had undergone coarse grinding as in Test No. 2 of Table 2 was micro-grinded using both a dry ball mill (Test 2) and a wet ball mill (Test 5), and then granulated into pellets as in Table 2, and the crushing strength was measured. The proportion of particles with a diameter of +1 mm before micro-grinding, the proportion of particles with a diameter of -63 μm after micro-grinding, and the results of the crushing strength measurements of the pellets are shown in Table 4 below. As shown in Table 4, the proportion of particles with a diameter of -63 μm in Test No. 5 was larger than that in Test No. 2. This result indicates that the micro-grinding efficiency of iron ore is higher when using a wet ball mill compared to using a dry ball mill.

[0060] [Table 4]

[0061]

[0062] Industrial availability

[0063] The ore crushing method of the present invention can efficiently pulverize iron ore into fine particles even when the iron ore contains iron ore that is difficult to finely pulverize, by pre-coarse crushing. In this way, the finely pulverized iron ore exhibits excellent granulation properties, and therefore this crushing method is industrially useful for use as a raw material for sintered ore and in the manufacture of pellets.

[0064] Explanation of reference numerals in the attached figures

[0065] 1. Rotating container

[0066] 2 balls

[0067] 3. Processing materials

[0068] 10. Crusher (Ball Mill)

Claims

1. A method for crushing ore, specifically a method for crushing ore containing iron ore, wherein... After coarsely crushing the iron ore with an average pore size of less than 10 μm to reduce the proportion of particles larger than 1 mm, the coarsely crushed iron ore is then micro-crushed to increase the proportion of particles smaller than 63 μm. The average pore size was determined by mercury porosimetry according to JIS R1655:2003, with the pore size distribution calculated as 50% of the cumulative pore volume from pore size 3.6 nm to 200 μm.

2. The ore crushing method as described in claim 1, wherein, The iron ore is coarsely crushed such that the proportion of particles with a diameter of 1 mm or more is 30% or more by mass before coarse crushing, and the proportion of particles with a diameter of 1 mm or more is reduced to 20% or less by mass.

3. The ore crushing method as described in claim 1 or 2, wherein, The iron ore is micronized in such a way that the proportion of particles smaller than 63 μm is 70% or more by mass.

4. The method for crushing ore according to any one of claims 1 to 3, wherein, Micronization was performed using a wet ball mill.

5. A method for manufacturing iron ore pellets, wherein, Iron ore raw materials comprising iron ore crushed by the crushing method according to any one of claims 1 to 4 are granulated to produce pellets.

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