JP6361335B2 - Method for producing sintered ore - Google Patents

Description

  The present invention relates to a method for producing a sintered ore.

  Among the iron ores used as raw materials in the ironmaking process, fine ores with an average particle size of 10 mm or less (average particle size of 1 to 3 mm) have a small particle size, so if they are put into a blast furnace as they are, they may cause clogging in the blast furnace. There is a possibility. That is, the flow path of the reducing gas in the blast furnace may be hindered by the fine ore. Therefore, the powdered ore is not put into the blast furnace as it is, but agglomerates (carbon materials such as powdered coke and anthracite), auxiliary materials (limestone, peridotite, serpentine, silica, etc.) and miscellaneous materials (scale, return). Sintered ore together with ore etc.) and put into the blast furnace. Hereinafter, the raw materials used for the production of sintered ore are collectively referred to as a raw material for sintering. A raw material in which all or part of the raw materials for sintering are blended at a predetermined ratio is also referred to as a blended raw material.

  In addition, in recent years, in view of the fact that the supply of high-grade fine ore (which contains a lot of hematite and contains a small amount of gangue components (silicon dioxide, alumina, etc.)) has been reduced, etc. It is expected to be used as a raw material. The fine ore is a concentrate produced by pulverizing a raw ore that originally has a low iron content until the particle size is usually 0.1 mm or less, and selecting the crushed raw material to increase the iron content. For example, fine ore contains 60 mass% or more of iron with respect to the total mass. Fine ore is usually used as a raw material for pellets (fired pellets). The surplus fine powder ore is called pellet feed (hereinafter also referred to as “PF”) and is distributed as a raw material for sintering.

  The fine ore and fine ore are granulated together with a binder such as quick lime and slaked lime as necessary in addition to the coagulant, the auxiliary raw material, and the miscellaneous raw material for the purpose of increasing the productivity of the sintered ore. As shown in Patent Document 1, finely pulverized iron ore may be added to a blended raw material. The finely pulverized iron ore assists the binder. Then, a packed bed of granulated material is formed in the sintering machine, and this packed bed is baked and hardened (fired) to produce a sintered cake. Specifically, the surface of the packed bed is ignited, and air is sucked downward through the packed bed. Thereby, the carbonaceous material in a mixing raw material burns, and the temperature of a packed bed is heated to about 1300 degreeC. When the temperature of the packed bed exceeds 1200 ° C, the calcium oxide source (for example, limestone) in the blended raw material reacts with a part of the iron ore and melts. When the charcoal combustion is completed, the packed bed is subsequently cooled by the sucked air. This melt is mainly solidified as calcium ferrite, and the remaining (unmelted) iron ore is combined to form a sintered body (sintered cake). And a sintered ore is produced by crushing and sizing the sintered cake.

JP 2013-32568 A

By the way, in recent years, the content of silicon dioxide is 3 to 6% by mass with respect to the total mass of fine ore, and the content of particles having a particle size of 63 μm or more is 90% by mass or more with respect to the total mass of fine ore. There is an increasing need to use certain fine ores. Hereinafter, such fine ore is also referred to as high SiO ₂ fine ore. High SiO ₂ fine ore is produced, for example, in Canada.

The blended raw material forms pseudo particles (granulated material) after granulation. At this time, since the fine ore is fine, it is usually located in the adhered powder layer in the pseudo particles. Since the high SiO ₂ fine powder ore contains a relatively large number of coarse particles, when the sintering raw material containing the high SiO ₂ fine powder ore is granulated as it is, many large pores are formed in the adhering powder layer of the pseudo particles. . The high SiO ₂ fine ores, because it contains a relatively large number of coarse grains decreases the contact area between the limestone and the high SiO ₂ fine ore. Therefore, it becomes difficult to produce calcium ferrite during sintering. On the other hand, high SiO ₂ fine ore has a high silicon dioxide content. Therefore, a large amount of silicon dioxide melt is produced during sintering. The melt of silicon dioxide is also called silicate slag. This silicate slag has a higher viscosity than calcium ferrite.

Therefore, since the ratio of the silicate slag in the melt of calcium ferrite and silicate slag is increased, the viscosity of the melt is increased. Furthermore, as described above, many large pores are formed in the adhered powder layer. Therefore, the melt is liable to stay in the pores, so that it is difficult for the melt to reach the entire adhered powder layer. As a result, the strength of the sintered ore, that is, the yield is lowered, and the production rate is also lowered. Thus, when the raw material for sintering comprising high SiO ₂ fine ore directly granulated, yield and production rate of the sinter is lowered. As will be described later, this problem becomes prominent when the amount of the calcium oxide source adhering to the high SiO ₂ fine ore is small (CaO / Ore is low). In addition, since the technique disclosed in Patent Document 1 is intended to improve the granulation property of the raw material for sintering, this problem cannot be solved at all.

Therefore, the present invention has been made in view of the above problems, and the object of the present invention is to obtain a sintered ore yield when a sintered ore is produced using a high SiO ₂ fine ore. And it is providing the manufacturing method of the new and improved sintered ore which can improve a production rate.

  In order to solve the above problems, according to an aspect of the present invention, the content of silicon dioxide is 3 to 6% by mass with respect to the total mass of fine ore, and the content of particles having a particle size of more than 63 μm is fine. A fine ore that is 90% by mass or more with respect to the total mass of the ore, a particle having a particle size of 20 μm or less is 20% by mass or more with respect to the total mass of the fine ore, and a particle having a particle size larger than 63 μm Including a step of pre-grinding until the content of 70% by mass or less with respect to the total mass of fine ore, and a step of granulating a blended raw material containing pre-ground fine ore and a calcium oxide source A method for producing a sintered ore is provided.

Here, the mass granulation system may be used, and the CaO equivalent mass of the calcium oxide source may be 0.1 or less in mass ratio with respect to the raw material excluding the calcium oxide source .

In addition, using the selective granulation system, the raw material granulated in any one of the granulation lines constituting the selective granulation system contains finely pulverized ore and calcium oxide source, and the calcium oxide source is converted into CaO The mass may be 0.1 or less by mass ratio with respect to the raw material granulated by one granulation line excluding the calcium oxide source.

As described above, according to the present invention, since the high SiO ₂ fine ore is pre-ground to a predetermined particle size, the yield and production rate of the sintered ore can be improved.

It is explanatory drawing which shows an example of the granulation system which concerns on this embodiment. It is explanatory drawing which shows the other example of the granulation system concerning the embodiment. It is a graph which shows the correspondence of CaO / Ore and the intensity | strength of the experimental sintered compact for every kind of PF. It is a graph which shows the correspondence of CaO / Ore and the intensity | strength of the experimental sintered compact for every kind of PF. It is an optical microscope photograph which expands and shows the cross section of the experimental sintered compact produced using solid Canadian PF. It is an optical microscope photograph which expands further and shows the cross section of the experimental sintered compact produced using solid Canadian PF. It is an optical microscope photograph which expands and shows the cross section of the experimental sintered compact produced using Canadian PF after pre-grinding. It is an optical microscope photograph which expands and shows the cross section of the experimental sintered compact produced using Canadian PF after pre-grinding.

  Exemplary embodiments of the present invention will be described below in detail with reference to the accompanying drawings. In addition, in this specification and drawing, about the component which has the substantially same function structure, duplication description is abbreviate | omitted by attaching | subjecting the same code | symbol. Further, the particle size in the present embodiment is measured using, for example, sieves having different mesh sizes. For example, a sieve having an opening of 0.25 mm is prepared, and the material to be measured is passed through this sieve. The raw material that has passed through this sieve has a particle size of 0.25 mm or less. On the other hand, the raw material remaining on the sieve has a particle size larger than 0.25 mm.

<1. About High SiO ₂ Fine Ore>
In the method for producing sintered ore according to the present embodiment, the yield and production rate of sintered ore are improved while using high SiO ₂ fine ore as a raw material for sintering. Therefore, first, the characteristics of the high SiO ₂ fine ore that is the object of the present embodiment will be described.

The high SiO ₂ fine powder ore has a silicon dioxide content of 3 to 6% by mass with respect to the total mass of the high SiO ₂ fine powder ore, and the content of particles having a particle size of 63 μm or more is the total of the high SiO ₂ fine powder ore. It is 90 mass% or more with respect to mass. Thus, the high SiO ₂ fine ore contains a relatively large amount of coarse particles and has a high silicon dioxide content.

An example of the high SiO ₂ fine ore is Canadian fine ore (Canada PF). That is, the raw ore (host rock) mined from the Canadian deposit contains many iron oxide particles (crystal particles) and gangue component particles (silicon dioxide particles, etc.) having a particle size of several hundreds of μm. Moreover, the particle sizes of the iron oxide particles and the gangue component particles are distributed within a range of 63 μm to 1000 μm. The raw ore is in a state where iron oxide particles and gangue component particles are bound to each other.

  The PF is generally manufactured by the following steps. That is, the ore is pulverized to separate the ore into iron oxide simple particles and gangue component simple particles. Here, the “single particle” means a particle that is not bonded to other types of particles. Then, the PF is prepared by selecting the crushed raw ore (specifically, separating and removing gangue component simple particles from the crushed raw ore). Examples of the beneficiation method include specific gravity beneficiation (a beneficiation method that uses a difference in specific gravity between iron oxide single particles and gangue component single particles to separate them). Here, the greater the degree of pulverization of the ore (for example, the longer the pulverization time), the more the ore can be separated into single particles of iron oxide and single particles of gangue components. In specific gravity beneficiation, the more single particles occupy the ore, the higher the accuracy of the beneficiation. For example, the mass% of silicon dioxide in the fine ore after the beneficiation decreases.

  However, even if the single particles are further pulverized, only the particle size of the single particles is reduced. Even if the particle size of a single particle changes, the accuracy of specific gravity beneficiation remains almost unchanged. Therefore, as the degree of pulverization is increased, the accuracy of specific gravity beneficiation almost reaches its peak. In this state, most of the iron oxide particles and silicon dioxide particles are single particles. There is a beneficiation method that is more accurate than specific gravity beneficiation, but it costs more.

  Here, Canadian ore has a larger particle size of iron oxide particles and silicon dioxide particles than other ore (for example, Brazil), so even if the degree of pulverization of the ore is light (that is, pulverization) Many iron oxide particles and silicon dioxide particles can be made into single particles, even if the size of the subsequent ore is large). On the other hand, the accuracy of specific gravity ore concentrates reaches an early stage (that is, while the degree of grinding is small). For this reason, although the beneficiation can be performed at a low cost, a relatively large amount of silicon dioxide remains in the PF.

  Therefore, Canadian PF contains a relatively large amount of coarse grains and has a high silicon dioxide content. Table 1 shows a composition example of Canadian PF. For comparison, a composition example of Brazilian PF is also shown.

In Table 1, “T.Fe”, “FeO”, “CaO”, “SiO ₂ ”, “Al ₂ O ₃ ”, “MgO”, “P”, “S”, “Mn”, and “CW” Indicates the mass% of all iron (divalent iron and trivalent iron), divalent iron, calcium oxide, silicon dioxide, alumina, magnesium oxide, phosphorus, sulfur, manganese, and crystal water relative to the total mass of PF, respectively. . Iron is present as hematite or magnetite in PF. Moreover, the mass% of bivalent iron is a FeO conversion value.

<2. Study by the Inventor>
As described above, when the sintering raw material containing high SiO ₂ fine powder ore is granulated as it is, many large pores are formed in the adhering powder layer in the pseudo particles. Furthermore, when the pseudo particles are sintered, the viscosity of the melt increases. For this reason, the melt tends to stay in the pores, and is difficult to spread throughout the sintering raw material. As a result, the yield and production rate of sintered ore is reduced.

Therefore, the present inventor investigated how the particle size of the high SiO ₂ fine ore and the viscosity of the melt affect the yield of the sintered ore. Here, the present inventor paid attention to CaO / Ore (reference mass ratio) as a parameter indicating the viscosity of the melt. CaO / Ore is a value obtained by dividing the terms of CaO mass of calcium oxide source is added to the high SiO ₂ fine ore on the total weight of the high SiO ₂ fine ore.

  Here, the reason why the CaO equivalent mass is used for the mass of the calcium oxide source is that the calcium oxide source is considered to be changed to calcium oxide during firing. For example, limestone is decarboxylated during firing to become CaO, which reacts with iron oxide and melts.

Therefore, CaO / Ore is a parameter indicating how much calcium oxide source is added to the high SiO ₂ fine ore. The higher the CaO / Ore, the more calcium oxide source is associated with the high SiO ₂ fine ore. Therefore, the higher the CaO / Ore, the greater the amount of calcium ferrite in the melt. That is, the viscosity of the melt decreases.

Although the details will be described in the examples described later, the present inventor made a tablet made of a mixture of high SiO ₂ fine powder ore and limestone simulating the adhering powder layer in the pseudo particles, and calcined this tablet (baking) The sintered body for experiment was created. And this inventor measured the intensity | strength of the sintered compact for experiment. Then, the present inventors have conducted the same process is repeated while changing the particle size distribution and CaO / Ore high SiO ₂ fine ore. Here, the strength of the experimental sintered body is an index indicating the yield of sintered ore. Moreover, since the raw material for sintering other than the high SiO ₂ fine powder ore and limestone is not included in the mixture, almost all of the limestone adheres to the high SiO ₂ fine powder ore. Therefore, CaO / Ore is obtained by dividing the CaO equivalent mass of limestone by the total mass of high SiO ₂ fine ore.

As a result, the inventor found that the strength of the experimental sintered body produced using solid (ie, not pre-ground) high SiO ₂ fine ore was CaO / Ore = 0.1. It has been found that changes greatly. Specifically, the strength of the experimental sintered body produced using solid high SiO ₂ fine ore is very low when CaO / Ore is 0.1 or less, but CaO / Ore is low. When / Ore exceeds 0.1, it greatly increases.

Therefore, when CaO / Ore is 0.1 or less, it is considered that the above-described problem occurs. On the other hand, when CaO / Ore exceeds 0.1, the viscosity of the melt is sufficiently low, so even if the pores of the adhering powder layer are large, the melt is added to the entire high-SiO ₂ fine ore. Is thought to be prevalent.

On the other hand, a high SiO ₂ fine ore, the content of the particles size is 20μm or less is 20 mass% or more with respect to the total weight of the high SiO ₂ fine ore, and the content of the particle size is 63μm larger particles Is pre-ground until the total mass of the high SiO ₂ fine ore reaches 70% by mass or less, the strength of the experimental sintered body increases regardless of the value of CaO / Ore.

The present inventor considers this reason as follows. First, when CaO / Ore is 0.1 or less, the composition of the melt is the same as that of the prior art, so the viscosity is high. However, since the high SiO ₂ fine ore is pre-ground, the pores in the mixture are reduced. Further, the gap between the high SiO ₂ fine ores is also reduced. Therefore, it is believed that the melt by capillary action spreads to the entire height SiO ₂ fine ore. That is, the melt is used more effectively. On the other hand, when CaO / Ore exceeds 0.1, the viscosity of the melt is sufficiently low, so it is considered that the melt spreads throughout the high SiO ₂ fine ore. For the above reasons, when the high SiO ₂ fine ore is pre-ground, the strength of the experimental sintered body is increased regardless of the value of CaO / Ore.

As a result of the above examination, the present inventor has conceived the method for producing a sintered ore according to the present embodiment. In the method for producing a sintered ore according to the present embodiment, when CaO / Ore is 0.1 or less, the sintered ore is prepared after pre-grinding the high SiO ₂ fine ore. The manufacturing method of sintered ore according to the present embodiment, when the CaO / Ore exceeds 0.1, to produce a sintered ore with high SiO ₂ fine ore after Yusugata or pre grinding. In the latter case, it is preferable to produce a sintered ore using solid high SiO ₂ fine ore in consideration of the cost for pre-grinding.

<3. Application example>
The method for producing sintered ore according to the present embodiment can be realized by, for example, the collective granulation system 1a shown in FIG. 1, the selective granulation system 1b shown in FIG. First, an example of the batch granulation system 1a will be described with reference to FIG.

(3-1. Configuration of batch granulation system)
The batch granulation system 1a is a system that batch granulates high SiO ₂ fine powder ore and powder ore. It comprises a crusher 2, a drum mixer 3 and a sintering machine 4. The pulverizer 2 pre-grinds the high SiO ₂ fine ore. The high SiO ₂ fine ore after the pre-grinding is put into the drum mixer 3. The drum mixer 3 granulates the solid or pre-ground high SiO ₂ fine ore and the remaining raw material for sintering to produce a granulated product of the blended raw material. The remaining raw materials for sintering are raw materials excluding high SiO ₂ fine ore. Table 2 shows an example of the composition of the blended raw materials.

In Table 2, the mass% of each raw material is mass% with respect to the total mass of the blended raw materials. However, the mass% of return or coke is an outside number. “Aus A” to “Aus D” mean Australian fine ores. “Bra A” and “Bra B” mean Brazilian fine ores, respectively. Canadian PF1 is a target of crushing and Canadian PF, and the composition is shown in Table 1. “CaO” means quicklime. In the example of Table 2, the sources of calcium oxide attached to the high SiO ₂ fine ore are limestone and quicklime. Slaked lime may be further included as a calcium oxide source. Moreover, you may use slaked lime instead of quick lime. Quicklime and slaked lime serve as a binder. When slaked lime is included in the remaining raw materials for sintering, the calcium oxide source adhering to the high SiO ₂ fine powder ore includes slaked lime.

In the batch granulation system 1a, the high SiO ₂ fine powder ore and the remaining raw materials for sintering are granulated at once. At this time, there is a possibility that the high SiO ₂ fine powder ore and the calcium oxide source adhere with a probability described later. The granulated material of the blending raw material is put into the sintering machine 4. The sintering machine 4 forms a packed bed of blended raw materials and sinters this packed bed to produce a sintered cake. And the sintering machine 4 crushes a sintered cake, and also produces a sintered ore by carrying out the granulation in a post process (not shown).

(3-2. Manufacturing method of sintered ore using batch granulation system)
In the sintered ore manufacturing method using the batch granulation system 1a, first, the value of CaO / Ore is calculated. Here, in the batch granulation system 1a, the high SiO ₂ fine powder ore and the remaining sintering raw material containing the calcium oxide source are batch granulated, so the calcium oxide source contains the high SiO ₂ fine powder ore and the remaining Of the raw materials for sintering, they adhere to raw materials other than the calcium oxide source (hereinafter also simply referred to as “other raw materials for sintering”).

Here, it is considered that the calcium oxide source adheres to the high SiO ₂ fine powder ore and other raw materials for sintering according to their mass ratio. Therefore, the CaO / Ore molecule, that is, the CaO equivalent mass of the calcium oxide source adhering to the high SiO ₂ fine ore is expressed by the following formula (1).

In Equation _{(1), Wt CaO} is CaO reduced mass of the calcium oxide source to adhere to the high SiO ₂ fine ore, a is the total mass of the high SiO ₂ fine powder ore, b is the raw material for other sintering This is the total mass, and c is the CaO equivalent mass of the calcium oxide source. Therefore, CaO / Ore is expressed by the following formula (2).

Therefore, CaO / Ore is substantially equivalent to the CaO equivalent mass of the calcium oxide source in all the blended raw materials (high SiO ₂ fine powder ore + the remaining raw materials for sintering), high SiO ₂ fine powder ores and other sintered materials. It is obtained by dividing by the total mass of raw materials (total mass of raw materials other than calcium oxide source in all blended raw materials).

In the present production method, when the CaO / Ore formula 2 is 0.1 or less, introducing a high SiO ₂ fine ore crusher 2. The pulverizer 2 is a high SiO ₂ fine powder ore, in which the content of particles having a particle size of 20 μm or less is 20% by mass or more based on the total mass of the high SiO ₂ fine powder ore, and the particle size is larger than 63 μm. Is previously pulverized until the content of is 70% by mass or less based on the total mass of the high SiO ₂ fine ore. It is preferable that the pulverizer ₂ pulverizes the high SiO ₂ fine ore until the maximum particle size of the particles becomes 125 μm or less. The high SiO ₂ fine ore after the pre-grinding is put into the drum mixer 3. The drum mixer 3 granulates the pre-ground high SiO ₂ fine ore and the remaining raw materials for sintering.

On the other hand, when CaO / Ore exceeds 0.1, high SiO ₂ fine ore is put into the drum mixer 3 as it is. The drum mixer 3 granulates the solid high SiO ₂ fine ore and the remaining sintering raw material. The high SiO ₂ fine ore may be put into the drum mixer 3 after being pulverized by the pulverizer 2 in the same manner as described above, but from the viewpoint of cost, it may be put into the drum mixer 3 as it is. preferable. When importance is attached to the yield of sintered ore, it is preferable to pre-grind high-SiO ₂ fine ore. In this case, it is preferable that the pulverizer ₂ pulverizes the high SiO ₂ fine ore until the maximum particle size of the particles becomes 125 μm or less. The blended raw material granulated material produced by the drum mixer 3 is put into the sintering machine 4. And the sintering machine 4 produces a sintered ore using the granulated material of a mixing | blending raw material.

The calculation of CaO / Ore may be performed automatically. For example, a control device that controls the collective granulation system 1a may be provided, and the control device may be allowed to calculate CaO / Ore. It may also be introduced Redirecting high SiO ₂ fine ore based on the calculation result of the CaO / Ore also to perform the control device. The control device includes hardware configurations such as a CPU, a ROM, a RAM, a hard disk, and various drive devices, and the functions described above are realized by these hardware configurations. The ROM stores a program for causing the control device to realize the functions described above, and the CPU reads and executes this program. The calculation of CaO / Ore and the change of the input destination of the high SiO ₂ fine powder ore based on the calculation result of CaO / Ore may be performed artificially.

(3-3. Configuration of selective granulation system)
Next, the selective granulation system 1b will be described based on FIG. The selective granulation system 1b is a system for selectively (separately) granulating high-SiO ₂ fine ore and fine ore. A pulverizer 2, a pan pelletizer 2a, a drum mixer 3 and a sintering machine 4 are used. With.

The pulverizer 2 pre-grinds the high SiO ₂ fine ore. The pan pelletizer 2a granulates the first sintering raw material to produce a granulated product of the first sintering raw material. Here, for the first sintered material comprises a high SiO ₂ fine ore and the binder after pre crushing. Examples of the binder include quick lime and slaked lime. Of these, at least one may be included in the first sintering material. Further, the first sintering raw material may include fine ore having a smaller particle size than the high SiO ₂ fine ore. By including such fine powder ore in the first sintered raw material, the function of the binder is improved. Hereinafter, such fine ore is also referred to as “auxiliary binder”. An example of the auxiliary binder is disclosed in Patent Document 1. The granulated product of the first raw material for sintering is put into the sintering machine 4 together with the granulated product of the second raw material for sintering. As described above, in the selective granulation system 1b, the first sintering raw material is selectively granulated. Therefore, when calculating CaO / Ore, it is only necessary to focus on the first sintering raw material.

  The drum mixer 3 produces a granulated product of the second sintering raw material by granulating the second sintering raw material. Here, the second sintering raw material is obtained by removing the above-described first sintering raw material from the total sintering raw material. The granulated product of the second sintering raw material is charged into the sintering machine 4 together with the first sintered raw material granulated product. The sintering machine 4 forms a packed bed of granulated material, and sinters this packed bed to produce a sintered cake. And the sintering machine 4 produces a sintered ore by crushing a sintered cake, and also sizing in a post process.

(3-4. Manufacturing method of sintered ore using selective granulation system)
Also in the manufacturing method of the sintered ore using the said selective granulation system 1b, the value of CaO / Ore is first calculated. Here, in the selective granulation system 1b, since the first sintering raw material is selectively granulated, attention should be paid to the first sintering raw material. Usually, in a selective granulation system, the calcium oxide source is used as a binder (eg, quicklime, slaked lime). When an auxiliary binder is used, the calcium oxide source adheres to the high SiO ₂ fine powder ore and the auxiliary binder.

Here, it is considered that the calcium oxide source adheres to the high SiO ₂ fine powder ore and the auxiliary binder according to their mass ratio. Therefore, the numerator of CaO / Ore is represented by the following formula (1 ′).

In Formula (1), Wt _CaO is the CaO equivalent mass of the calcium oxide source adhering to the high SiO ₂ fine powder ore, a ′ is the total mass of the high SiO ₂ fine powder ore, and b ′ is the total mass of the auxiliary binder. And c ′ is the CaO equivalent mass of the total calcium oxide source in the first sintering raw material. Therefore, CaO / Ore is expressed by the following mathematical formula (2 ′).

Therefore, CaO / Ore substantially means the CaO equivalent mass of the total calcium oxide source in the first sintering raw material, and the total mass of the high SiO ₂ fine ore and the auxiliary binder (that is, the first sintering source). Divided by the total mass of raw materials other than the calcium oxide source in the raw material. When the auxiliary binder is not included in the first sintering raw material, b ′ = 0.

In the present production method, when the CaO / Ore is 0.1 or less, introducing a high SiO ₂ fine ore crusher 2. And the grinder 2 grinds the high SiO ₂ fine ore in advance. Here, the pulverizer 2 has a high SiO ₂ fine ore particle content of 20 μm or less with a particle size of 20 μm or less and a high SiO ₂ fine particle size of 63 μm or greater with respect to the total mass of the high SiO ₂ fine ore. until the content of ₂ fine ore particles is 70 mass% or less based on the total weight of the high SiO ₂ fine powder ore, pre-crushed high SiO ₂ fine ore. It is preferable that the pulverizer ₂ pulverizes the high SiO ₂ fine powder ore until the maximum particle size of the high SiO ₂ fine powder ore particles is 125 μm or less. The first sintering raw material including the high SiO ₂ fine ore and the binder after the pre-grinding is put into the pan pelletizer 2a. The pan pelletizer 2a granulates the first sintering raw material after pre-grinding to produce a granulated product of the first sintering raw material. The granulated product of the first sintering raw material is charged into the sintering machine 4 together with the granulated product of the second sintering raw material.

On the other hand, when CaO / Ore exceeds 0.1, the first sintering raw material containing the high SiO ₂ fine powder ore and the binder is put into the pan pelletizer 2a as it is. And the punch pelletizer 2a granulates the solid first raw material for sintering to produce a granulated product of the first raw material for sintering. The high SiO ₂ fine ore may be put into the pan pelletizer 2a after being pre-ground by the pulverizer 2 in the same manner as described above. preferable. When importance is attached to the yield of sintered ore, it is preferable to pre-grind high-SiO ₂ fine ore. In this case, it is preferable that the pulverizer ₂ pulverizes the high SiO ₂ fine ore until the maximum particle size of the high SiO ₂ fine fine ore particles is 125 μm or less. The granulated product of the first sintering raw material is charged into the sintering machine 4 together with the granulated product of the second sintering raw material.

  On the other hand, the drum mixer 3 produces a granulated product of the second sintering material by granulating the second sintering material. The granulated product of the second sintering raw material is put into the sintering machine 4 together with the granulated product of the first sintering raw material. And the sintering machine 4 produces a sintered ore using the granulated material of the 1st raw material for sintering, and the granulated material of the 2nd raw material for sintering.

The calculation of CaO / Ore and the change of the input destination of the high SiO ₂ fine ore based on the calculation result of CaO / Ore may be performed automatically or artificially.

(1. Preparation of raw materials)
Next, examples of the present embodiment will be described. In this example, Canadian PF1 shown in Table 1 was used as the high SiO ₂ fine ore. This Canadian PF1 has a solid, wet-sieved average particle size (average particle size) of 387 μm, and the content of particles having a particle size of 20 μm or less is 0.33% by mass relative to the total mass of Canadian PF, and the particle size is from 63 μm. The large particle content is 97.4% by mass relative to the total mass of Canadian PF.

  Here, the average particle diameter of each ore was calculated by the following method. That is, ore is sieved wet using eight types of sieves with openings of 1.0, 0.5, 0.25, 0.18, 0.125, 0.063, 0.045, and 0.020 mm. It was. From the obtained mass ratio for each particle size, it was assumed that there was no specific gravity difference for each particle size of iron ore, and the average particle size was calculated with reference to Appendix J of JIS M 8706. Specifically, the average particle size was calculated based on the following formula (3).

  Here, APS is an average particle size (mm), fi is a mass fraction (% by mass) for each particle size category, and di is an intermediate sieve (mm) of the particle size category.

  Further, the preliminary pulverization of Canadian PF1 was performed by the following two methods. (Pulverization Method 1) 50 kg of Canadian PF1 was pulverized for 5 minutes with a small ball mill. The resulting Canadian PF (hereinafter also referred to as “BM-pulverized Canadian PF”) has a wet sieving average particle size of 146 μm, and the content of particles having a particle size of 20 μm or less is the total mass of BM-pulverized Canadian PF. On the other hand, the content of the particles having a particle size of 21.2% by mass and larger than 63 μm was 62.7% by mass with respect to the total mass of the BM-ground Canadian PF. (Pulverization Method 2) Canadian PF1 was pulverized with a fret mill until the maximum particle size became 125 μm or less. The resulting Canadian PF (hereinafter also referred to as “FM-ground Canadian PF”) has a wet sieving average particle size of 44 μm, and the content of particles having a particle size of 20 μm or less is the total mass of FM-ground Canadian PF. On the other hand, the content of particles having a particle size of 39.4% by mass and a particle size larger than 63 μm was 29.5% by mass with respect to the total mass of the FM pulverized Canadian PF. In pulverization method 2, the degree of pulverization is greater than in pulverization method 1.

  For comparison, a Brazilian PF shown in Table 1 was prepared. This Brazilian PF has a wet sieving average particle size of 108 μm, a content of particles with a particle size of 20 μm or less is 8.9% by mass relative to the total mass of the Brazilian PF, and a content of particles with a particle size greater than 63 μm is Brazil It is 43.5 mass% with respect to the total mass of production PF. Further, Brazilian PF was pre-ground by the above-described (grinding method 1). The Brazilian PF after pre-grinding is also referred to as “BM-milled Brazilian PF”.

(2. Reactivity (anabolic) test)
In order to simulate the reaction between the calcium oxide source in the granulated product and each PF, the following assimilation test was performed. First, each PF and limestone having a particle size of 0.5 mm or less were mixed so that CaO / Ore was in the range of 0.05 to 0.15, and an 8 mmφ × 10 mmH tablet was produced using this mixture. In addition, when producing a tablet, since materials other than PF and limestone are not included in the mixture, CaO / Ore can be obtained by dividing the total mass of limestone by the total mass of PF. And the sintered compact for experiment was produced by baking these tablets. The firing pattern was approximated to a real sintering machine. Specifically, the tablet was heated from 1100 ° C. to 1300 ° C. in 1 minute and cooled from 1300 ° C. to 1100 ° C. in 3 minutes.

  Then, a +0.5 mm yield test and an optical microscope observation were performed on the experimental sintered body. In the +0.5 mm yield test, a 300 g weight from 300 mm above the experimental sintered body was dropped three times. Thereafter, the pulverized experimental sintered body was passed through a sieve having an opening of 0.5 mm, and the mass% of the particles remaining on the sieve (+0.5 mm particles) with respect to the total mass of the experimental sintered body was measured. +0.5 mm particles have a particle size greater than 0.5 mm. As the mass% of the +0.5 mm particles increases, the strength of the experimental sintered body increases. Therefore, the mass% of the +0.5 mm particles was defined as the strength of the experimental sintered body. The strength of the experimental sintered body is an index of sintered ore yield (+5 mm yield).

  3 and 4 show the measurement results. First, the measurement result of Canadian PF is compared with the measurement result of Brazilian PF. When CaO / Ore is low (0.05 to 0.10), the strength of the experimental sintered body produced using solid Canadian PF1 is very small. The strength of the experimental sintered body produced by use is very high. On the other hand, there is a large difference between the strength of the experimental sintered body made using solid Brazilian PF and the strength of the experimental sintered body made using BM-ground Brazilian PF. I couldn't find it. Thus, with low CaO / Ore, the strength of the experimental sintered body could be greatly improved by pre-grinding Canadian PF1. Furthermore, the strength improvement effect by pre-grinding was greater for Canadian PF than for Brazil PF.

Since Canadian PF1 has a large particle size, the surface area where limestone and PF particles are in contact with each other is also small. Therefore, when a tablet containing solid Canadian PF1 and having a low CaO / Ore is baked, the reaction between limestone and PF particles does not proceed sufficiently, and a sufficient amount of calcium ferrite is not generated. Furthermore, since Canadian PF1 contains a large amount of silicon dioxide, a large amount of silicate slag is produced during firing. For this reason, the ratio of the silicate slag in the melt increases. And silicate slag has a high viscosity. For this reason, the viscosity of the melt is increased. Furthermore, since Canadian PF1 has a large particle size, many large pores are formed in the tablet.
For this reason, the melt stays in the pores, and does not reach the entire Canadian PF1. Furthermore, these pores remain in the experimental sintered body (see FIG. 5). For the above reasons, the strength of the experimental sintered body is lowered.

  On the other hand, when a tablet containing BM-ground Canadian PF and having a low CaO / Ore is baked, the viscosity of the melt is high as in the case of solid. However, since Canadian PF is pre-ground, the pores in the tablet are small and the gap between Canadian PF is also small. For this reason, the melt easily spreads throughout the Canadian PF due to the capillary phenomenon, and as a result, the strength of the experimental sintered body increases.

  On the other hand, Brazilian PF does not contain as much silicon dioxide as Canadian PF, so the viscosity of the melt is low even when CaO / Ore is low. Furthermore, the particle size of Brazilian PF is smaller than Canadian PF1. Therefore, regardless of the presence or absence of pre-grinding, the melt easily spreads throughout the Brazilian PF, and as a result, the strength of the experimental sintered body increases.

  On the other hand, when CaO / Ore is high (exceeding 0.10 to 0.15), the strength of the experimental sintered body produced using solid Canadian PF1 and BM ground Canadian PF were used. There was no significant difference between the strength of the experimental sintered body produced in this way. In this case, since the viscosity of the melt is lowered, it is considered that the melt spread throughout the Canadian PF even when it is solid. A similar trend was seen in Brazilian PF.

  For the above reasons, with low CaO / Ore, the strength of the experimental sintered body can be greatly improved by pre-grinding Canadian PF1. Furthermore, the strength improvement effect by pre-grinding is greater for Canadian PF than for Brazil PF.

  Next, the difference in measurement results depending on the degree of grinding was examined. As shown in FIG. 4, it was found that the strength increases as the degree of pulverization increases in both cases where CaO / Ore is low and high. Further, the difference in strength was noticeable when CaO / Ore was high. According to these results, it was found that a sufficient effect can be obtained by pulverization of about (Crushing Method 1). Moreover, when CaO / Ore is high and it is desired to place importance on the yield of sintered ore, it was found that Canadian PF1 may be pulverized until the maximum particle size of the particles becomes 125 μm or less.

  In the optical microscope observation, the experimental sintered body was cut along a vertical section passing through its center, and this section was polished. Thereafter, the cross section was observed with an optical microscope. Optical micrographs of vertical sections are shown in FIGS. All of the experimental sintered bodies were produced under the condition of CaO / Ore = 0.1. The experimental sintered bodies shown in FIGS. 5 and 6 were produced using solid Canadian PF1, and the experimental sintered bodies shown in FIGS. 7 and 8 were BM-ground Canadian PF. It was produced using. 5 and 7 show the macrostructure of the vertical cross section at the same magnification. 6 and 8 show the microstructure of the central portion of the vertical cross section at the same magnification.

  As shown in FIG. 5, a large number of large pores exist in the vertical cross section of the experimental sintered body produced using the solid Canadian PF1. Furthermore, the shape of the pores is also indefinite. These pores are formed due to the large particle size of the solid Canadian PF1. On the other hand, as shown in FIG. 7, almost no large pores as shown in FIG. 5 are formed in the vertical cross section of the experimental sintered body produced using BM-ground Canadian PF, and many small pores are formed. Is done. Also, the shape of each pore is close to a circle. This suggests that the reaction between BM ground Canadian PF and limestone has progressed, and the rearrangement of pores has progressed.

  As shown in FIG. 6, in the vertical cross section of the experimental sintered body produced using the solid Canadian PF1, melt (indicated by CF + SS) is gathered in coarse pores, and PF particles ( It was not fully utilized for bonding between each other). In this way, the melt is difficult to spread throughout the Canadian PF1. On the other hand, as shown in FIG. 8, in the vertical cross section of the experimental sintered body produced using the solid Canadian PF1, the melt is sufficiently diffused between the PF particles. It was used for binding. Thus, the melt is easy to spread throughout the BM-ground Canadian PF. For this reason, it is considered that the strength of the experimental sintered body was improved. Moreover, residual coarse grains are also eliminated. The coarse grain interface can cause strength defects. Therefore, it is considered that the strength of the experimental sintered body was improved also from this point.

(2. Sintering pot test)
In order to confirm that the product yield (+5 mm yield) and production rate of sintered ore were improved by pulverization of Canadian PF1, a sintering pot experiment described below was conducted.

  The blend (base) of the reference example was a blend obtained by removing Canadian PF from the raw materials for sintering shown in Table 2. The composition of the comparative examples and examples was as shown in Table 2. Furthermore, Canadian PF1 of the comparative example was used as it was, and in the example, it was used after pulverizing with BM. The wet sieving average particle size after pulverization was 146 μm, the content of particles having a particle size of 20 μm or less was 21.2% by mass, and the content of particles having a particle size greater than 63 μm was 62.7% by mass. CaO / Ore of the comparative example and the example were both 0.088 (smaller than 0.1).

Next, after mixing the whole amount of each compounding raw material with a drum mixer (diameter 1000 mm × length 400 mm) for 1 minute, 7.0% of water was added and granulation was performed for 4 minutes. The granulated product of each compounding raw material was charged into a 300 mmφ sintering pan with a layer thickness of 600 mm and fired at a constant negative pressure of 1200 mmH ₂ O. The ignition time was 90 seconds. The firing time was the time from the start of ignition until the windbox temperature reached the maximum. FFS (frame front speed) was obtained by dividing the layer thickness by the sintering firing time.

  The product yield was measured as follows. That is, the produced sintered ore (sintered cake) was dropped five times from a height of 2.0 m. Then, the crushed sintered ore was passed through a sieve having an opening of 5 mm, and the mass percentage of the particles (+5 mm particles) remaining on the sieve with respect to the total mass of the sintered ore was defined as the product yield (+5 mm yield). Moreover, the production rate was calculated | required as the mass of the unit area (unit area of planar view) of a sintering pot, and + 5mm particle | grains obtained per unit time. The results of the sintering pot experiment are shown in Table 3.

  When the reference example and the comparative example are compared, in the comparative example, the FFS and the yield are lowered, and the production rate is also lowered. The decrease in FFS is considered to be affected by the particle size distribution and surface shape, which are difficult to granulate. The decrease in yield is thought to be due to the poor assimilation at low CaO / Ore. On the other hand, when the comparative example and the example were compared, in the example, although the FFS was comparable to the comparative example, the yield was greatly improved. This is considered to be due to the effect of grinding.

As described above, according to the present embodiment, the yield and production rate of the sintered ore are improved by pre-grinding the high SiO ₂ fine ore. This effect is particularly prominent when CaO / Ore is low (0.1 or less).

  The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings, but the present invention is not limited to such examples. It is obvious that a person having ordinary knowledge in the technical field to which the present invention pertains can come up with various changes or modifications within the scope of the technical idea described in the claims. Of course, it is understood that these also belong to the technical scope of the present invention.

1a, 1b Granulation system 2 Crusher 2a Pamperetizer 3 Drum mixer 4 Sintering machine

Claims (3)

The fine ore wherein the content of silicon dioxide is 3 to 6% by mass with respect to the total mass of the fine ore, and the content of particles having a particle size larger than 63 μm is 90% by mass or more with respect to the total mass of the fine ore The content of particles having a particle size of 20 μm or less is 20% by mass or more based on the total mass of the fine ore, and the content of particles having a particle size greater than 63 μm is 70% based on the total mass of the fine ore. A step of pre-grinding until the mass% or less,
And a step of granulating a blended raw material containing the finely divided ore after pre-grinding and a calcium oxide source. It is a manufacturing method of the sintered ore of Claim 1, Comprising:
Using a batch granulation system,
Characterized in that CaO reduced mass of the calcium oxide source is 0.1 or less in mass ratio with respect to the raw material except for the source of calcium oxide, sinter manufacturing method of.   It is a manufacturing method of the sintered ore of Claim 1, Comprising:
  Use selective granulation system,
  The raw material granulated in any one granulation line constituting the selective granulation system includes the pre-ground fine ore and the calcium oxide source,
The sintered ore characterized in that the CaO equivalent mass of the calcium oxide source is 0.1 or less in mass ratio with respect to the raw material granulated by the one granulation line excluding the calcium oxide source. Manufacturing method.