JP7587142B2 - Sinter manufacturing method - Google Patents

Description

The present invention relates to a method for granulating fine raw materials in the production of sintered ore. In particular, the present invention relates to a method for granulating fine raw materials using a separate granulation method.

In recent years, the amount of gangue components ( _SiO2 · _Al2O3 ) in iron ore has increased due to the depletion and deterioration of iron ore resources. Therefore, it will be important in the future to increase the amount of fine ore (also called concentrate or pellet feed ₍ PF)) that has been artificially treated to have a high Fe content in the ore _dressing process and maintain or reduce the gangue components ( _SiO2 · _Al2O3 ) in iron ore in the production of sintered ore.

Therefore, technological development is being carried out to granulate fine ore using selective and separate granulation equipment to produce coarse granules with diameters of 5 to 15 mm, which are then charged into a sintering machine together with raw materials processed using conventional granulation equipment to reduce the amount of ungranulated powder, and to avoid the deterioration of the air permeability of the raw material packed bed caused by the fine ore and the drop in productivity [Non-Patent Document 1].

Known types of fine ore include hematite (Fe ₂ O ₃ ) fine ore and magnetite (Fe ₃ O ₄ (FeO.Fe ₂ O ₃ )) fine ore. Patent Document 1 discloses a method of using magnetite fine ore alone.

Also, Non-Patent Document 2 indicates the finding that magnetite-based fine ore, even without the addition of CaO, has a post-sintering strength equivalent to that of hematite-based fine ore to which CaO is added.
Furthermore, Patent Document 2 shows that when granulating hematite-based fine ore, the strength of the granulated product is improved by adding fine ore as nuclei to the fine ore in a ratio (fine ore/fine ore) of 1.5/1 or more and less than 3/1.

JP 2013-253281 A JP 2016-191122 A

T. K. Sandeep et al: Metallurgical and Materials Transaction B, Volume 46B, No 2 (2015), 635 T. K. Sandeep et al. :Metallurgical and Materials Transaction B, Volume 47B, No. 1 (2016), 309

As will be described in detail later, when a large amount of magnetite-based fine ore is used, for example, the strength of sintered ore increases. For this reason, there is a growing demand to produce sintered ore using as much magnetite-based fine ore as possible. However, magnetite-based fine ore is often processed into pellets at a pellet factory near the mine or at the shipping port before being shipped. For this reason, the amount of magnetite-based fine ore currently circulating in the iron ore sea trade market is small. Therefore, as in the method described in Patent Document 1, it is not feasible to use magnetite-based fine ore as the entire amount of iron ore used as the raw material for sintered ore without using hematite-based fine ore. In addition, there has been no study to date on the use of hematite-based fine ore and magnetite-based fine ore in combination. In the method described in Patent Document 2, the addition of fine ore as a nucleus is considered, but there has been no study to date on the use of hematite-based fine ore and magnetite-based fine ore in combination while using such fine ore as a nucleus.

The object of the present invention is to provide a method for producing sintered ore that can replace magnetite-based fine ore with easily purchased hematite-based fine ore while suppressing a decrease in the strength of the sintered ore after firing. In other words, the present invention clarifies the range of substitution in which a granulated material in which a portion of magnetite-based fine ore has been replaced with hematite-based fine ore is equivalent to a granulated material made only of magnetite-based fine ore in terms of handleability during sintered ore production and sintered ore strength after firing.

The inventor first conducted a basic experiment using an electric furnace to measure the strength of a mixture of magnetite-based fine ore and hematite-based fine ore after sintering. The inventor then clarified that if the mixture contains magnetite-based fine ore at a mixing ratio of 50% by mass or more, the sintered product of the mixture exhibits a strength equivalent to that of a sintered product containing only magnetite-based fine ore. Next, the inventor conducted a sintering experiment under practical raw material blending conditions. As a result, the inventor confirmed that the strength of the sintered ore can be obtained by setting the mixing ratio of magnetite-based fine ore to the total mass of hematite-based fine ore and magnetite-based fine ore within the above range, as well as the strength of the sintered ore, which is equivalent to that of the magnetite-based fine ore alone (i.e., the magnetite-based fine ore alone is used as the fine ore of the iron-containing raw material).
The present invention was devised based on the results of such investigations, and the gist of the present invention is as follows.

The gist of the present invention is as follows.
According to one aspect of the present invention, there is provided a method for producing sintered ore, which comprises: dividing a sintering raw material into a main sintering raw material and a sub-sintering raw material containing fine ore; performing a main granulation process for mixing and granulating the main sintering raw material in parallel with a sub-granulation process for mixing and granulating the sub-sintering raw material; combining the granulated products produced in the main granulation process and the sub-granulation process; and firing the combined granulated product to produce sintered ore. The fine ore used in the sub-granulation process is a mixture of magnetite-based fine ore and hematite-based fine ore, and the mixing ratio of the magnetite-based fine ore to the total mass of the magnetite-based fine ore and the hematite-based fine ore is 50% by mass or more and less than 100% by mass.
Here, the particle size of the magnetite-based fine ore is preferably equal to or smaller than the particle size of the hematite-based fine ore.
Furthermore, it is preferable that the auxiliary sintering raw material further contains fine ore, and the mass ratio of the fine ore to the fine ore is 1.5/1 or more and less than 3/1.

Magnetite-based fine ore can be replaced with hematite-based fine ore while preventing a decrease in the strength of the sintered ore after firing.

FIG. 1 is a schematic diagram of an apparatus used in a basic experiment using an electric furnace. FIG. 1 is a diagram showing the relationship between the mixing ratio (mass%) of magnetite-based fine ore and the average particle size (mm) after dropping. FIG. 2 is a diagram showing a schematic flow of a granulation processing system (granulation device). FIG. 2 is a diagram showing a schematic configuration of an apparatus used in a sintering experiment (pot test).

A preferred embodiment of the present invention will be described in detail below with reference to the attached drawings. Each raw material used in this embodiment is an aggregate of many particles. Unless otherwise specified, the name of each raw material refers to the aggregate of particles that make up that raw material. A numerical range expressed using "~" refers to a range that includes the numerical values written before and after "~" as the lower and upper limits. Numerical values indicated as "greater than" or "less than" are not included in the numerical range.

<Basic studies leading to the present invention>
When hematite fine ore is mixed with magnetite fine ore, it is considered that the strength changes depending on the mixing ratio of magnetite fine ore due to the difference in the properties of hematite fine ore and magnetite fine ore. Therefore, the change in strength when hematite fine ore is mixed with magnetite fine ore was experimentally investigated.

(Experimental Method and Conditions)
Hematite-based fine ore (sometimes referred to as H in this experiment) and magnetite-based fine ore (sometimes referred to as M in this experiment) were used as samples (Table 1). In order to examine the effects of the mixing ratio and particle size combination of magnetite-based fine ore, each ore was sieved into 20-45 μm and 63-125 μm. Here, in the particle size range by sieve classification, "A-B μm" indicates the particle size range of the ore that remains on the sieve with mesh size A (μm) and falls through the sieve with mesh size B (μm). In sieve classification, "A-B μm" indicates A or more and less than B. Hereinafter, hematite fine ore with a size of 20 to 45 μm will be referred to as H-fine, and 63 to 125 μm as H-coarse. Similarly, magnetite fine ore with a size of 20 to 45 μm will be referred to as M-fine, and 63 to 125 μm as M-coarse. Table 1 also shows the compositions of H-fine, H-coarse, M-fine, and M-coarse. The compositions were determined by chemical analysis.

A total of 29 samples were prepared by changing the mixing ratio by 7 to 9 levels under four combination conditions (two levels of ore type and two levels of particle size). These samples were then used to examine the effects of the mixing ratio and particle size combination of magnetite-based fine ore.

Specifically, first, about 3.6% water was added to about 1.6 g of a mixture of two types of fine ore (two types from among H fine, H coarse, M fine, and M coarse) mixed at a specified mixing ratio, and the mixture was filled into a die and subjected to a pressure of 4.8 MPa for 30 seconds. This produced a cylindrical tablet with a diameter of 8 mm and a height of about 10 mm.

The molded tablets were then fired in an electric furnace with a heat pattern simulating that of an actual sintering machine (heating rate 200°C/min, maximum temperature reached 1300°C, maximum temperature holding time 0 seconds, cooling rate 67°C/min). The equipment used for firing is shown diagrammatically in Figure 1. A drop weight test was conducted in which a 300g load was dropped from a height of 30cm three times on the fired tablets. After the drop weight test, the samples were sieved to calculate the average particle size (average particle size) and evaluate the strength. (Hereinafter, this will be referred to as the average particle size after dropping.) Specifically, sieves with mesh sizes of 4.75 mm, 2.8 mm, 2.0 mm, 1.0 mm, 0.5 mm, 0.25 mm, and 0.125 mm were stacked to perform sieving, and the average value of each sieve and the next higher sieve was taken as the representative particle size (for example, 2.4 mm for 2.0 to 2.8 mm), and the weighted average value was calculated as the sum of the products of the representative particle size and the weight ratio. From the perspective of the strength of the actual sintered ore, it is considered necessary for the average particle size after dropping to be 1.5 mm or more in order to ensure the minimum sintered ore strength without forming localized weak parts. It is more preferable for the average particle size after dropping to be 2.5 mm or more, as this will provide sufficiently high strength.

Four tablets of each level were fired, three were subjected to a drop weight test, and one was embedded in resin and polished for cross-sectional structure observation and image analysis. In addition, one tablet each with a mixing ratio of magnetite-based fine powder ore of 25 mass%, 50 mass%, and 75 mass% was molded, and then embedded in resin without firing, polished, and subjected to cross-sectional structure observation and image analysis.

(Experimental Results)
The change in the average particle size after the weight drop is shown in Figure 2. Under all different particle size combination conditions, the average particle size after the weight drop, i.e., the strength after firing, increased with an increase in the mixing ratio of magnetite-based fine ore (here, M fine or M coarse). However, the increase in strength was not constant; when the mixing ratio of magnetite-based fine ore was less than 25 mass%, there was almost no increase, and when the mixing ratio was 25 to 50 mass%, the increase was particularly large, and after 50 mass%, the slope became gentle again, and when the mixing ratio was 75 mass% to 80 mass%, the strength value was roughly equivalent to that of magnetite-based fine ore alone (100%). It was also found that the tablet had a higher strength in the combination containing M fine.

(Action)
There are three bonding mechanisms for the granulated product of magnetite-based fine ore and hematite-based fine ore: (1) bonding between magnetite particles, (2) bonding between magnetite particles and hematite particles, and (3) bonding between hematite particles. Of these, (1) has a stronger bonding strength than (2) and (3). This is thought to be because magnetite particles are oxidized by the temperature rise accompanying the sintering reaction and change into hematite particles, and the changes in crystal structure and volume at that time promote diffusion bonding between particles. Therefore, the strength is improved by increasing the amount of magnetite-based fine ore.

Furthermore, when the mixing ratio of magnetite-based fine ore is 50% by mass or more, the bonds in (1) form a network throughout the entire granulated material. Once this network is formed throughout the entire granulated material, the strength improvement thereafter becomes gradual. Therefore, when the mixing ratio of magnetite-based fine ore is 50% by mass or more, the strength of the tablet becomes roughly equal to the strength value of a tablet made from magnetite-based fine ore alone.

Here, it is considered that the combination of raw materials with different particle sizes affects the network formation. In the case of the combination of H coarse and M fine, the fine magnetite particles fill the periphery of the hematite particles and the gaps between the particles, and the network of (1) with high bonding strength is easily formed as in the combination of H fine and M fine. On the other hand, in the case of the combination of H fine and M coarse, the fine hematite particles with weak bonding strength fill the periphery of the magnetite particles and the gaps between the particles, and the network of (1) with high bonding strength is inhibited.
In the case of the combination of H coarse and M coarse, the number of particles and therefore the number of contact points between the particles are small, so the strength is also low. However, in any combination of particle sizes, if the mixing ratio of magnetite fine ore is 50 mass% or more, the average particle size after dropping is 1.5 mm or more.

<Embodiments>
The present invention has been devised based on the above-mentioned fundamental studies, and is a method for producing sintered ore having a secondary granulation process for selectively strengthening the granulation of fine raw materials, characterized in that the fine raw materials are a mixture of hematite-based fine ore and magnetite-based fine ore, and the mixing ratio of the magnetite-based fine ore to the total mass of both is 50 mass% or more and less than 100 mass%.
Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

(Overall composition)
Fig. 3 shows the flow of the granulation process system in this embodiment. This granulation process is a raw material processing method known as selective granulation or divided granulation. As shown in Fig. 3, in this granulation process, the sintering raw material is divided into a main sintering raw material group 11 and a sub-sintering raw material group 21, and these are mixed and granulated. Specifically, in this granulation process, a main granulation process 1 for granulating the main sintering raw material group 11 and a sub-granulation process 2 for granulating the sub-sintering raw material group 21 are performed in parallel. After that, the granulated products 3 produced in the main granulation process 1 and the sub-granulation process 2 are combined, and the combined granulated products 3 are fired in a sintering machine 4.

(Main granulation process)
In the main granulation process 1, a predetermined amount of the main sintering raw material group 11 is supplied from a hopper 111 to a conveyor 112, and the main sintering raw material group 11 is blended on the conveyor 112. The conveyor 112 supplies the blended raw materials of the main sintering raw material group 11 to a drum mixer 12. The blended raw materials of the main sintering raw material 11 are mixed and granulated in the drum mixer 12 to produce granulated products 13 of pseudo particles. The main sintering raw material group 11 includes an iron-containing raw material, an auxiliary raw material, return ore, dust, and carbonaceous material. The main sintering raw material group 11 is the remaining raw materials excluding the raw materials selected as the auxiliary sintering raw material group 21 described below.

In Figure 3, a connected tandem type drum mixer is arranged, but multiple drum mixers may be arranged in series, or mixing and granulation may be performed using a single drum mixer.

(Secondary granulation process)
In the secondary granulation process 2, a predetermined amount of the secondary sintering raw material group 21 is supplied from a hopper 2111 to a conveyor 2112, and the secondary sintering raw material group 21 is blended on the conveyor 2112. The conveyor 2112 supplies the blended raw material of the secondary sintering raw material group 21 to a granulator. The blended raw material of the secondary sintering raw material 11 is then mixed and granulated in the granulator to produce a granulated product 24 of pseudo-particles. The granulator is preferably, for example, a combination of a high-speed stirring mixer 22 and a dish-type pelletizer 23 in this order. The granulator is not limited to the above example, as long as the former has a high mixing and stirring function and the latter has a high granulation function.

Table 2 shows an example of the composition of the auxiliary sintering raw material group 21. The mixing ratio of the auxiliary sintering raw material group 21 is preferably in the range of 15% by mass to 30% by mass with respect to the total mass of the entire blended raw materials (the blended raw materials of the main sintering raw material 11 and the auxiliary sintering raw material 21). If it is less than 15% by mass, the effect of improving productivity is low, and if it exceeds 30% by mass, there is a possibility that processing will not be possible due to insufficient equipment capacity.

The secondary sintered raw material group 21 mainly contains fine powder raw material 211, which is the target for strengthening granulation. In the secondary granulation process 2, the fine powder raw material 211 is selectively strengthened in granulation. This is because the drum mixer 12 used as a granulator in the main granulation process 1 is not suitable for granulating the fine powder raw material 211.

The feature of the present invention is that the fine powder raw material 211 is a mixture of hematite-based fine ore 211a and magnetite-based fine ore 211b. Furthermore, the mixing ratio of magnetite-based fine ore 211b is 50 mass% or more and less than 100 mass% with respect to the total mass of magnetite-based fine ore 211b and hematite-based fine ore 211a. As explained in FIG. 2, by making the mixing ratio of magnetite-based fine ore 211b 50 mass% or more, the same post-sintering strength as when magnetite-based fine ore is used alone can be obtained.

In embodiment 1 of Table 2, the mixing ratio of magnetite-based fine ore and hematite-based fine ore is 50 mass % each. Examples of hematite-based fine ore include concentrates from Brazil and Canada. Examples of magnetite-based fine ore include concentrates from North America, South America, Europe, Australia, and Africa.

Because the fine raw materials are shipped after being dressed at each iron mine, they have a certain particle size distribution according to their mineralogical characteristics and processing process. Methods for measuring particle size distribution include sieve passing weight rate and laser diffraction/scattering method, and evaluation indices include median diameter (cumulative 50% mass diameter) and average particle size.

In the above-mentioned basic study results, the post-sintering strength was low in the case of the combination of H-coarse + M-coarse, in which both the hematite-based fine ore and the magnetite-based fine ore were 63 to 125 μm, but sufficient strength was obtained in other combinations. In addition, the post-sintering strength was particularly high in the combination of H-fine and M-fine, and in the combination of H-fine and M-coarse. Therefore, in the method described in the present invention, it is preferable that the particle size of the magnetite-based fine ore is equal to or smaller than the particle size of the hematite-based fine ore. In addition, the preferred particle size of the hematite-based fine ore is less than 125 μm, and the preferred particle size of the magnetite-based fine ore is less than 45 μm. More preferably, the particle sizes of both the hematite-based fine ore and the magnetite-based fine ore are less than 45 μm. The smaller the particle size of the magnetite-based fine ore, the more the productivity and the like tend to improve. The more preferred particle size of the magnetite-based fine ore is 15 μm or less. Additionally, there is no particular lower limit on the particle size for any of the fine ores.

In order to promote the granulation of the fine raw material in the secondary granulation process 2, fine ore (core ore) 212, which serves as the nucleus of granulation, may be used in addition. The strength of the granulated product after granulation is highest when the mass ratio of the fine ore to the fine ore (core ore) is 1.5/1 or more and less than 3/1 (fine ore/fine ore). The core ore may be sinter feed (hereinafter referred to as SF), which is usually used in the production of sintered ore. Specifically, limonite-based ores are preferred because the fine raw material has strong adhesion when the ore is used as a granulation nucleus. The embodiment 2 shown in Table 2 is an example in which 1/3 mass% (mass% of the total mass of the fine ore and the fine ore) of Australian limonite is used as the core ore.

To promote granulation of the fine powder raw materials, a binder such as quicklime can be used as appropriate. In the case of quicklime, it is preferable to use 5 mass% or less of the total mass of the auxiliary sintering raw materials. In embodiment 3, in addition to embodiment 2, quicklime is used in an amount of 0.5 mass% of the total mass of the entire blended raw materials (2.2 mass% of the total mass of the auxiliary sintering raw materials).

In addition, the raw materials mixed in the secondary granulation process 2 can contain any sintered raw materials as long as they do not inhibit the granulation of the fine powder raw materials.

In order to confirm the feasibility and effectiveness of the present invention, a sinter pot test was conducted to investigate the effect of the ratio of fine ore used in the secondary granulation process on sinter productivity and sinter strength in the granulation process shown in Figure 3. The results are described below as an example. The present invention is not limited to this example. Various conditions can be adopted in the present invention as long as they do not deviate from the gist of the present invention and the object of the present invention is achieved.

(Experimental Equipment)
The main specifications of the experimental equipment used in the sintering experiment are shown in Table 3, and the configuration of the experimental equipment is shown in Figure 4. The sintering pot consists of the pot body and a wind box located below it. A thermocouple is inserted in the wind box, and the sintering completion point is determined based on the point at which the temperature reaches its maximum. A pressure gauge is inserted in the wind box to measure the negative pressure under the pot. The wind box is connected to the suction blower by piping. The piping is equipped with a gas sampling probe (pump for component analysis) connected to a gas component analyzer (component analysis device), and an orifice flow meter for measuring the flow rate. The ignition furnace is installed above the sintering pot during ignition and can be moved to a retreat position during sintering. The granulators (not shown) used to granulate the raw materials were drum-type for the main line and Eirich-type and pan-type batch-type for the side line.

(Experimental Method and Conditions)
(Raw material blend)
In this embodiment, the hematite-based fine ore 211a was made of ore H1 produced in Brazil, and the magnetite-based fine ore 211b was made of ore M1 produced in Sweden. The particle sizes were measured by a laser diffraction/scattering method, and the average particle sizes were calculated to be 26 μm and 19 μm, respectively.

Furthermore, as a verification example of the use of finer magnetite-based fine ore, Australian magnetite-based fine ore M2 was used. The average particle size was 14 μm.

Tables 4 and 5 show the raw material blends for the main granulation process and the secondary granulation process. The raw material blends for the main granulation process were all constant. The mixing ratio of magnetite-based fine ore and hematite-based fine ore in the secondary granulation process was set to a total of 15.0 mass% (relative to the total mass of the blended raw materials of the main sintering raw materials and the secondary sintering raw materials), and tests were conducted in which the mixing ratio of magnetite-based fine ore (mass% relative to the total mass of the hematite-based fine ore and the magnetite-based fine ore) was changed to 0 mass%, 25 mass%, 50 mass%, 75 mass%, and 100 mass%. In addition, fine ore (core ore) that serves as the nucleus of granulation was also used. The core ore was limonite (fine ore) from Australia. The mixing ratio of the core ore was set to a constant 7.5 mass% (relative to the total mass of the blended raw materials of the main sintering raw materials and the secondary sintering raw materials).

In the sintering process, it is customary to include return ore, which is generated as a by-product during firing and recycled as a raw material, and carbonaceous materials such as coke powder that are burned and lost during firing. The total of so-called new raw materials excluding these is 100% by mass, and the total raw materials including return ore and carbonaceous materials is 119.7% by mass.

(Granulation)
In the main granulation process, the main sinter raw material, return ore and fine coke were charged into a drum mixer and mixed for 2 minutes. After that, the raw materials were further granulated by rolling for 3 minutes and 45 seconds while pouring a predetermined amount of water into the mixer so that the moisture content was 7.0%.

In the secondary granulation process, the secondary sintering raw materials were fed into a high-speed agitating mixer, water was added, and the mixture was mixed and stirred for 1 minute. Next, the mixture was fed into a pan pelletizer at 1 wet-kg, and the discharged granules were collected one by one.

Next, the granules produced in the main granulation process and the secondary granulation process were lightly mixed in the drum mixer for 15 seconds to combine these granules.

(Pot roasting)
The granulated material (combined granulated material) produced in the granulation process was charged into a sintering pot to form a raw material packed bed. Next, the surface of the raw material packed bed was ignited and time measurement was started. Here, ignition was performed by heating the surface of the raw material packed bed at 1300°C for 1 minute in an ignition furnace while continuing downward suction at a constant air volume (1.5 Nm ³ /min). After ignition, the raw material packed bed was fired at a constant negative pressure below the pot of 9.8 kPa. The firing end time was the time when the exhaust gas temperature (measured by a thermocouple installed in the wind box) showed a maximum value, and the firing time was the time from the start of ignition to the end of firing. Three minutes after the end of firing, the blower was stopped and the sintered cake was collected from the pot. Thermocouples were also placed in the middle layer, lower layer, and under the pot of the sintering pot to measure the temperature changes in each layer.

The sintered cake obtained after the firing was dropped four times from a height of 2 m, then classified using a square sieve with a diameter of 5 mm. The sieve-surface was regarded as the product sintered ore, and the product yield of +5 mm was evaluated. In addition, the productivity was calculated from the firing time and the product yield.

(Experimental Results)
The test results are shown in Table 6.
The productivity did not change between Comparative Example 1, in which the fine powder raw material in the secondary granulation process was only hematite fine powder, and Comparative Example 2, in which the mixing ratio of magnetite-based fine ore was 25% by mass. However, an improvement was observed from Example 1, in which the mixing ratio was 50% by mass, and Example 2, in which the mixing ratio was 75% by mass, obtained a value roughly close to that of the reference example, in which only magnetite fine powder was used.

Regarding particle size, a higher production rate was obtained in Example 3, which used finer magnetite-based fine ore M2 at a mixing ratio of 50 mass% magnetite-based fine ore, than in Example 1.

(Conclusion)
The results of the basic test described above were also confirmed in the sintering experiment. That is, it was confirmed that by setting the mixing ratio of magnetite-based fine ore to 50 mass% or more and further blending magnetite-based fine ore having a finer particle size than hematite-based fine ore, higher productivity can be obtained than by blending hematite-based fine ore alone.

Although the preferred embodiment of the present invention has been described in detail above, the present invention is not limited to such examples. It is clear that a person with ordinary knowledge in the technical field to which the present invention pertains can conceive of various modified or revised examples within the scope of the technical ideas described in the claims, and it is understood that these also naturally fall within the technical scope of the present invention.

It can be used in a sintered ore manufacturing method that can replace magnetite-based fine ore with easily purchased hematite-based fine ore while suppressing the decrease in strength of the sintered ore after firing.

1: Main granulation process 11: Main sintering raw material 12: Drum mixer 13: Granules produced in 12 2: Secondary granulation process 21: Secondary sintering raw material group 211: Fine raw material to be granulated intensively 211a: Hematite-based fine ore 211b: Magnetite-based fine ore 212: Core ore 22: High-speed stirring mixer 23: Plate-type pelletizer 24: Granules produced in 22 and 23 3: Granules produced in the main granulation process and the secondary granulation process 4: Sintering machine

Claims (5)

A method for producing sintered ore, comprising the steps of: dividing a sintering raw material into a main sintering raw material and a secondary sintering raw material containing fine iron ore; carrying out a main granulation process in which the main sintering raw material is mixed and granulated; and a secondary granulation process in which fine iron ore, fine iron ore, and a binder are mixed and granulated as the secondary sintering raw material in parallel; combining the granules produced in the main granulation process and the secondary granulation process; and firing the combined granules,
The fine ore used in the secondary granulation step is a mixture of magnetite-based fine ore and hematite-based fine ore, and a mixing ratio of the magnetite-based fine ore to the total mass of the magnetite-based fine ore and the hematite-based fine ore is 50 mass% or more and less than 100 mass%. The method for producing sintered ore according to claim 1, wherein the fine ore is limonite. 3. The method for producing sintered ore according to claim 1 , wherein the particle size of the magnetite-based fine ore is equal to or smaller than that of the hematite-based fine ore. The method for producing sintered ore according to claim 3, characterized in that the magnetite-based fine ore has a particle size of 19 μm or less. 5. The method for producing sintered ore according to claim 1, wherein the auxiliary sintering raw material further contains fine ore, and a mass ratio of the fine ore to the fine ore is 1.5/1 or more and less than 3/1.

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