Method for producing sintered ore

Abstract

Provided is a method for producing sintered ore with high productivity, which does not require a step for pulverizing iron ore into fine powder and an expensive anionic polymer dispersant. Disclosed is a method for producing a sintered ore, which comprises granulating a raw material for sintering, which contains iron ores including a plurality of brands, together with added water by a granulator, and firing the granulated raw material for sintering by a sintering machine to obtain a sintered ore, some or all of the water added during granulation is replaced with a dust slurry solution in which solid dust is suspended in water at a concentration of 20-55 mass%.

Description

Technical Field

[0001] The present invention relates to a method for producing sintered ore as a raw material for a blast furnace, and more particularly to a method characterized by focusing on a granulation method of a sintering raw material. Background Art

[0002] Sintered ore is usually produced by the following process. First, the following substances are mixed in appropriate amounts into powdered iron ore (generally, called sintering raw material of about -10mm) including various brands to obtain sintering raw materials: auxiliary raw material powders such as limestone, silica, serpentine, etc.; miscellaneous raw material powders such as dust, scale, return ore, etc.; and solid fuels such as powdered coke. Next, water is added to the obtained sintering raw materials. Then, the sintering raw materials with added water are mixed-granulated to obtain sintering granulated raw materials. Next, the obtained sintering granulated raw materials are loaded into a sintering machine for sintering, thereby obtaining sintered ore. The sintering raw materials generally contain water and aggregate into quasi-particles during granulation. Then, when loaded onto the sintering trolley of the sintering machine, the quasi-particleized sintering granulated raw materials help to ensure good ventilation of the sintering raw material loading layer, so that the sintering reaction proceeds smoothly.

[0003] In the above-mentioned method for producing sintered ore, the water added to the sintering raw material during granulation has an appropriate water content. If the water content exceeds the appropriate value, only fine powders with small particle sizes will aggregate to form coarse particles with low strength. If the water content is lower than the appropriate value, ungranulated powder will be generated. Both of these will reduce the air permeability in the layer in which the sintering raw material is loaded, which will cause a decrease in productivity. On the other hand, when the sintering raw material is granulated, if fine powder is added, it can be used as a binder to suppress the generation of coarse particles and ungranulated powder during granulation.

[0004] For example, Patent Document 1 proposes a method of using an anionic polymer dispersant and using iron ore crushed to 10 μm or less as a binder.

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: Japanese Patent Application Publication No. 2013-32568 Summary of the invention

[0008] Problems to be solved by the invention

[0009] However, the technology proposed in Patent Document 1 has problems in that the iron ore needs to be pulverized to 10 μm or less and an expensive anionic polymer dispersant needs to be used.

[0010] An object of the present invention is to provide a method for producing a sintered ore with high productivity, which does not require either a step of pulverizing iron ore into fine powder or an expensive anionic polymer dispersant.

[0011] Means for solving problems

[0012] To achieve the above-mentioned object, the inventors of the present application studied a method of using dust with a particle size of several μm to several 100 μm generated in an iron and steel plant as a binder, and conceived of adding the dust in the form of a dust slurry solution in which solid dust is suspended in water.

[0013] That is, the present invention is a method for producing sintered ore, characterized in that a sintering raw material including iron ores of various brands is granulated together with added water using a granulator, and the obtained sintering granulated raw material is sintered using a sintering machine to obtain sintered ore. In the method for producing sintered ore, a part or all of the added water during the granulation is replaced with a dust slurry solution in which solid dust is suspended in water at a concentration of 20 to 55% by mass.

[0014] In addition, in the method for producing a sintered ore according to the present invention having the above-mentioned structure, the following solution is considered to be a more preferable solution.

[0015] (1) The solid dust is generated in the iron-making process and contains 50% by mass or more of dust having a particle size of -10 μm;

[0016] (2) concentrating the solid dust concentration to 30 to 50% by mass;

[0017] (3) Concentrating the solid dust concentration to 35-45% by mass;

[0018] (4) The method for concentrating the solid dust concentration is to use a concentrator to concentrate the solid dust.

[0019] Effects of the Invention

[0020] According to the method for producing sintered ore of the present invention, part or all of the water added during granulation is replaced with a dust slurry solution in which solid dust is suspended in water at a concentration of 20 to 55% by mass, thereby significantly improving the granulation of the sintering raw material. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] [ Figure 1 ] is a flow chart for illustrating an example of each step in the method for producing sintered ore of the present invention.

[0022] [ Figure 2 ] is a diagram for explaining an example of a phenomenon in the granulation process in the method for producing sintered ore of the present invention. DETAILED DESCRIPTION

[0023] Figure 1 This is a flow chart for explaining an example of each step in the method for producing sintered ore of the present invention. Figure 1 The various steps of the method for producing sintered ore of the present invention are described. First, powdered iron ores including various brands are prepared (step 1). Next, the auxiliary raw material powder, miscellaneous raw material powder, and solid fuel prepared in step S2 are appropriately mixed with the finely powdered iron ore prepared in step S1 to obtain a sintering raw material (step S3). Next, additional water is added to the obtained sintering raw material, and the sintering raw material is mixed and granulated (step S4) to obtain a granulated raw material for sintering (step S5). Next, the obtained granulated raw material for sintering is loaded into a sintering machine for sintering (step S6), thereby obtaining a sintered ore (step S7). In the present invention, a dust slurry solution formed by suspending solid dust in water is used to replace part or all of the additional water added during granulation (step S4).

[0024] According to the above Figure 1 , a sintering raw material including iron ores of various brands is granulated by a granulator, and the obtained sintering granulated raw material is sintered by a sintering machine. In the method for manufacturing sintered ore in which sintered ore is obtained, in the granulation process (step S4), as Figure 2 As shown, granules are generated through the stages of (1) generation of nuclei and (2) repeated granulation and disintegration of quasi-particles based on the nuclei. At this time, if fine powder is added, the fine powder acts as a binder, but if the fine powder and water are not evenly dispersed, for example, granules with low strength and ungranulated materials containing only fine powder will be produced. The inventors of the present application have found that when dust with a particle size of several μm to several 100 μm generated in an iron and steel plant is used as a binder, a dust slurry solution in which the dust is suspended in water at a concentration of 20 to 55% by mass is added to the granulation process, so that the fine powder and water are evenly dispersed and the granulation property is improved, thereby achieving high sintering productivity. For dust suspended in the dust slurry solution, for dust with a particle size of less than -10 μm, the transportability of the piping using the dust slurry is excellent and the effect of improving the granulation property is also excellent, so it is preferred to contain 50% or more of dust with a particle size of -10 μm.

[0025] That is, the greatest feature of the present invention is that a part or all of the water added during granulation is replaced by a dust slurry solution in which solid dust is suspended in water at a concentration of 20 to 55% by mass. In addition, the following method is considered to be a more preferred method: the solid dust is dust with a particle size of several μm to several 100 μm generated in the iron-making process; the concentration of the solid dust is concentrated to 30 to 50% by mass; the concentration of the solid dust is concentrated to 35 to 45% by mass; the method for concentrating the concentration of the solid dust is any one or more of natural sedimentation of a concentrator, gravity separation using a hydrocyclone, a decanter, etc., and forced dehydration using a filter press.

[0026] In addition, in the method for producing a sintered ore of the present invention described above, <particle size> is defined as follows.

[0027] <Particle size>

[0028] The particle size obtained by sieving using a sieve with a nominal mesh opening according to JIS (Japanese Industrial Standard) Z 8801-1, for example, a particle size of 1 mm or less means a particle size that all passes through a sieve with a nominal mesh opening of 1 mm according to JIS Z 8801-1, also recorded as -1 mm. In addition, the minimum value of the nominal mesh opening specified in JIS (Japanese Industrial Standard) Z 8801-1 is 20 μm, and when it is less than 20 μm, for example, 10 μm or less, it means a particle size at which the cumulative fraction of particle sizes of 10 μm or less determined by the laser diffraction and scattering method according to JIS 8825 or the liquid phase gravity sedimentation method according to JIS Z8820-2 is approximately 100%.

[0029] Example

[0030] The following experiments were actually conducted to examine the necessary and preferred configurations in the method for producing a sintered ore of the present invention.

[0031] <Example 1>

[0032] The slurry produced in the wet dust collection of the ironmaking process was collected and the solid concentration was measured, which was about 20% by mass. For the solid component, the particle size distribution was measured using a laser scattering particle size measuring device, and the result was that the weight ratio of -10μm relative to the solid component as a whole was approximately 100% by mass. Under the conditions of various changes in the slurry concentration, a granulation test of the mixed raw material of iron ore was carried out to confirm the granulation, transportability and sintering productivity. In the change of the slurry concentration, the natural sedimentation method was adopted. After the slurry was placed in a container and settled for a certain period of time, the supernatant water was removed and the slurry of the specified concentration was recovered.

[0033] First, a mixed raw material of iron ore (water content 5.5% by mass) is mixed and granulated using a drum mixer to obtain quasi-particles. At this time, water is added in a manner that becomes an appropriate granulation moisture. The result of a previous study is that the appropriate moisture value is 7.5% by mass, so the amount of water added is set in a manner that the total of the moisture contained in the slurry and the moisture added separately becomes 7.5% by mass. In the addition of water, a nozzle, pump, and piping for injection are constructed. The ore raw materials are added to the drum mixer, and water and slurry are added while the mixer starts to rotate. The total granulation time is 5 minutes.

[0034] Next, the quasiparticles were loaded into a 300 mm diameter v , a small iron sintering test pot with a height of 600mm, ignites the raw materials on the top of the filling layer, and conducts a sintering test. The sintered cake is dropped from a height of 2m once, and the +10mm ratio in the dropped sintered cake is defined as the finished product ratio. The productivity is calculated using the time required for sintering and the grate area of ​​the sintering machine tester.

[0035] According to the above-mentioned process, as shown in the following Table 1, for the examples of Inventive Examples 1 to 10 and Comparative Examples 1 to 3, the slurry transportability, mixing property in the drum mixer, and sintering productivity are compared. Here, Inventive Example 1 directly uses the collected slurry. Inventive Examples 2 to 8 are slurries in which the collected slurry is concentrated to a concentration of 20 to 55% by mass. Inventive Examples 9 and 10 are slurries in which the collected slurry is concentrated to a concentration of 20 to 55% by mass, and a part of the added water is replaced. Comparative Example 1 completely dries the slurry and uses it as a powder. Comparative Examples 2 and Comparative Examples 3 are slurries in which the collected slurry is concentrated and the concentrations are set to 15% by mass and 60% by mass, respectively.

[0036] The slurry transportability was evaluated by clogging of the pipe when adding the slurry to the mixer. The mixing performance in the drum mixer was evaluated by clogging of the nozzle. The productivity was evaluated by the pan test.

[0037] [Table 1]

[0038]

[0039] The following can be known from the results of Table 1. In Comparative Example 1, which shows the results of using the slurry completely dried as a powder, although the transportability is excellent, it absorbs moisture and aggregates in the drum mixer because it is an ultrafine powder, and the moisture does not spread to other ore raw materials, thereby generating a large amount of ungranulated powder. In Comparative Example 2, which shows the results of using the collected slurry diluted to a concentration of 15% by mass, although the transportability and mixing properties are excellent, a large difference in productivity is observed from Comparative Example 1. It is believed that this is because the ratio of fine powder loaded into the raw material is as low as 0.5% by mass, and no obvious effect is shown in terms of the binder effect. In Comparative Example 3, which shows the results of using the collected slurry concentrated to a concentration of 60% by mass, the viscosity of the slurry rises sharply, the properties become sludge, the piping is difficult to transport, and the spraying from the nozzle becomes difficult. As a result, the sludge cannot be mixed evenly with the raw material, ungranulated powder and coarse particles are generated, and the sintering productivity decreases.

[0040] On the other hand, compared with Comparative Examples 1 and 2, in Inventive Example 1 showing the results of the case where the collected slurry is directly used, the productivity is improved. In Inventive Examples 2 to 10 showing the results of the case where the collected slurry is concentrated to a concentration of 20 to 55% by mass, the sintering productivity is improved as the ratio of fine powder charged into the raw material increases. In addition, if Inventive Examples 2 to 10 are compared, in Inventive Examples 7 and 10, no problem was found in the transportability of the concentrated slurry, but clogging and the like occurred when spraying from the nozzle. As a result, compared with Inventive Example 6, the slurry in the drum mixer was not uniformly sprayed, ungranulated powder was produced, and the productivity was slightly reduced. In Inventive Example 8, the viscosity of the slurry increased, and clogging and the like were observed when transported by a pump and sprayed from the nozzle. As a result, compared with Inventive Example 7, the slurry in the drum mixer was not uniformly sprayed, ungranulated powder was produced, and the productivity was slightly reduced.

[0041] According to the above research, by comparing Inventive Examples 1 to 10 with Comparative Examples 1 to 3, it can be seen that by replacing part or all of the added water during granulation with a dust slurry solution in which solid dust is suspended in water at a concentration of 20 to 55% by mass, a sintered ore with high productivity can be obtained without the need for either the process of crushing iron ore into fine powder or the expensive anionic polymer dispersant. In addition, it can be seen that if the properties of dust particles are different, as a more preferred range, the solid dust in the dust slurry solution is 30 to 50% by mass, and it is further preferred that the solid dust in the dust slurry solution is 35 to 45% by mass.

[0042] <Example 2>

[0043] As a preferred embodiment, 10% by mass of high-grade fine powder ore (concentrate) of hematite system which is difficult to granulate is added to the sintering raw materials (45% by mass of Australian ore and 45% by mass of South American ore) to confirm the effect of adding the concentrated slurry. High-grade fine powder ore is a raw material with a higher specific gravity than ordinary raw materials and insufficient fine particles that contribute to adhesion. The particle size distribution is also narrow and the water permeability is high, but the adhesion is poor. Therefore, like the previous method, when the slurry is not used, there is a problem that it is easy to peel off during the rotation process in the drum mixer and produce ungranulated powder.

[0044] Therefore, in fact, as Inventive Example 10, the slurry with an initial concentration of 20 mass % was concentrated in the same manner as Inventive Example 9, a slurry with a concentration of 40 mass % was added and granulated, and then a sintering test was performed to obtain the productivity. As Comparative Example 5, a slurry with a concentration of 15 mass % was used, and a sintering test was performed in the same manner as Inventive Example 10 to obtain the productivity. The results are shown in Table 3 below. As can be seen from the results in Table 3, in Inventive Example 10, the productivity was improved compared to Comparative Example 5 due to the increase in the quasi-particle diameter and the shortening of the sintering time.

[0045] [Table 2]

[0046]

[0047] Industrial application areas

[0048] According to the method for producing sintered ore involved in the present invention, by replacing part or all of the added water during granulation with a dust slurry solution formed by suspending solid dust in water at a concentration of 20 to 55% by mass, the granulation of the sintering raw materials can be greatly improved. In addition to the exemplified contents, this production method can also be applied to various sintering raw materials.

Claims

1. A method for producing sintered ore, characterized in that: A sintering raw material including iron ores of various brands is granulated together with added water using a granulator, and the obtained sintering granulated raw material is fired using a sintering machine to obtain a sintered ore. In the method for producing the sintered ore, a part or all of the added water during the granulation is replaced with a dust slurry solution in which solid dust is suspended in water at a concentration of 20 to 55% by mass.

2. The method for producing sintered ore according to claim 1, wherein: The solid dust is generated in a steel-making process and contains 50 mass % or more of dust having a particle size of -10 μm.

3. The method for producing sintered ore according to claim 1 or 2, characterized in that: The solid dust is concentrated to a concentration of 30 to 50% by mass.

4. The method for producing sintered ore according to claim 1 or 2, characterized in that: The solid dust is concentrated to a concentration of 35 to 45% by mass.

5. The method for producing sintered ore according to claim 3, wherein: The method for concentrating the concentration of the solid dust is concentration using a concentrator.

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