Sinter manufacturing method

Abstract

The present invention proposes a method for producing a sintered ore with high productivity without requiring both an expensive anionic polymer dispersant and a step for grinding an iron ore into a fine powder. The present invention provides a method for producing a sintered ore, wherein a blended sintering starting material including iron ores of a plurality of brands is granulated together with additive water in a granulator, and the resultant granulated starting material for sintering is fired in a sintering machine so as to obtain a sintered ore. With respect to this method for producing a sintered ore, some or all of the additive water during the granulation is replaced with a dust slurry solution that is obtained by suspending solid dust in water at a concentration of 20-55 mass%.

Description

[Technical Field]

[0001] The present invention relates to a method for producing sintered ore, which is a raw material for a blast furnace, and in particular to a method characterized by focusing on a method for granulating a blended raw material for sintering. [Background technology]

[0002] Sinter is typically produced by the following process. First, various types of fine iron ore (generally sinter feed, typically about -10 mm in size) are mixed with appropriate amounts of auxiliary raw material powders such as limestone, silica, and serpentine, miscellaneous raw material powders such as dust, scale, and return fines, and solid fuel such as coke fines to obtain a sintering raw material blend. Next, water is added to the resulting sintering raw material blend. The water-added sintering raw material blend is then mixed and granulated to obtain granulated raw material for sintering. The granulated raw material for sintering is then loaded into a sintering machine and fired to obtain sintered ore. The sintering raw material blend typically contains moisture, which causes it to agglomerate during granulation and form pseudo-particles. When loaded onto the sintering machine's pallet, these pseudo-particled granulated raw material for sintering help ensure good ventilation in the sintering raw material bed, facilitating the sintering reaction.

[0003] In the above-mentioned method for producing sintered ore, there is an optimum moisture content for the water added to the sintering raw material mixture during granulation. If the moisture content exceeds the optimum value, only fine particles with small particle sizes will aggregate to form coarse particles with low strength. If the moisture content is below the optimum value, ungranulated powder will be generated. Both of these factors reduce the air permeability in the sintering raw material charging layer and cause a decrease in productivity. On the other hand, if fine powder is added when granulating the sintering raw material mixture, its action as a binder can suppress the generation of coarse particles and ungranulated powder during granulation.

[0004] For example, Patent Document 1 proposes a method in which iron ore pulverized to 10 μm or less is used as a binder using an anionic polymer dispersant. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-32568 Summary of the Invention [Problem to be solved by the invention]

[0006] However, the technique proposed in Patent Document 1 has the problems of requiring a step of crushing iron ore to a size of 10 μm or less and using an expensive anionic polymer dispersant.

[0007] An object of the present invention is to provide a highly productive method for producing sintered ore without requiring either a step of crushing iron ore into fine powder or an expensive anionic polymer dispersant. [Means for solving the problem]

[0008] In order to achieve the above object, the inventors have considered a method of utilizing dust generated in steelworks, which has a particle size of several μm to several hundred μm, as a binder, and have come up with the idea of ​​adding it as a dust slurry solution in which solid dust is suspended in water.

[0009] That is, the present invention provides a method for producing sintered ore, which comprises granulating a sintering blend raw material containing iron ore of multiple brands together with added water in a granulator, and firing the resulting granulated raw material for sintering in a sintering machine to obtain sintered ore, characterized in that part or all of the added water used 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 mass%.

[0010] In the method for producing sintered ore according to the present invention configured as described above, (1) The solid dust is generated in the steelmaking process and contains 50 mass% or more of particles with a particle size of -10 μm. (2) Enriching the solid dust concentration to 30 to 50 mass%; (3) Enriching the solid dust concentration to 35 to 45 mass%; (4) The method for thickening the solid dust concentration is thickening using a thickener. This is considered to be a more preferable solution. [Effects of the Invention]

[0011] According to the method for producing sintered ore of the present invention, by replacing part or all of the water added during granulation with a dust slurry solution in which solid dust is suspended in water at a concentration of 20 to 55 mass%, the granulation of the sintered mixed raw material can be significantly improved. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a flowchart illustrating an example of each step in a method for producing sintered ore according to the present invention. [Figure 2] 1 is a diagram for explaining an example of a phenomenon that occurs in a granulation process in the method for producing sintered ore of the present invention. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0013] FIG. 1 is a flowchart illustrating an example of each step in the sinter ore manufacturing method of the present invention. Each step in the sinter ore manufacturing method of the present invention will be explained with reference to FIG. 1. First, fine iron ore consisting of multiple brands is prepared (Step 1). Next, the fine iron ore prepared in Step S1 is blended with appropriate amounts of the auxiliary raw material powder, miscellaneous raw material powder, and solid fuel prepared in Step S2 to obtain a sintering blended raw material (Step S3). Next, additive water is added to the obtained sintering blended raw material, and the sintering blended 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 charged into a sintering machine and fired (Step S6) to obtain sintered ore (Step S7). In the present invention, some or all of the additive water added during granulation (Step S4) is replaced with a dust slurry solution in which solid dust is suspended in water.

[0014] In the sinter ore manufacturing method shown in FIG. 1, a sintering raw material blend containing multiple brands of iron ore is granulated in a granulator, and the resulting granulated raw material for sintering is fired in a sinter machine to produce sinter. In the granulation process (step S4), as shown in FIG. 2, granules are produced through the following steps: (1) nucleation; (2) repeated granulation and collapse of pseudo-particles using the nuclei. If fine powder is added during this process, the fine powder acts as a binder. However, if the fine powder and water are not uniformly dispersed, granules containing only fine powder may be produced, resulting in low-strength granules or ungranulated granules. The inventors discovered that, in order to utilize dust generated in steelworks with particle sizes ranging from several microns to several hundred microns as a binder, adding a dust slurry solution in which the dust is suspended in water at a concentration of 20 to 55 mass% during the granulation process results in uniform dispersion of the fine powder and water, improving granulation performance and achieving high sinter productivity. Regarding the dust to be suspended in the dust slurry solution, dust with a particle size of -10 μm or less is excellent in transportability through the dust slurry piping and is also effective in improving granulation properties, so it is desirable for the dust to contain 50 mass% or more of particles with a particle size of -10 μm.

[0015] That is, the greatest feature of the present invention is that 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 mass%. Furthermore, more preferred embodiments are considered to be those in which the solid dust generated in the steelmaking process has a particle size of several μm to several hundred μm, the solid dust concentration is increased to 30 to 50 mass%, or the solid dust concentration is increased to 35 to 45 mass%, and the method for increasing the solid dust concentration is one or more of the following: natural settling using a thickener, gravity separation using a hydrocyclone or a decanter, or forced dehydration using a filter press.

[0016] In the above-described method for producing sintered ore of the present invention, the term "particle size" refers to the following. <Particle size> This refers to the particle size sieved using a sieve with a nominal mesh size conforming to JIS (Japanese Industrial Standards) Z 8801-1. For example, a particle size of 1 mm or less refers to a particle size that passes entirely through a sieve with a nominal mesh size of 1 mm conforming to JIS Z 8801-1, also referred to as -1 mm. Furthermore, the minimum nominal mesh size specified in JIS (Japanese Industrial Standards) Z 8801-1 is 20 μm, and a particle size smaller than that, for example, 10 μm or less, refers to a particle size in which the cumulative fraction of particle sizes of 10 μm or less is approximately 100% as determined by a laser diffraction / scattering method conforming to JIS 8825 or a liquid-phase gravity sedimentation method conforming to JIS Z 8820-2. [Example]

[0017] The following tests were actually carried out to examine essential and preferred configurations for the method for producing sintered ore of the present invention.

[0018] Example 1 Slurry generated by wet dust collection in the steelmaking process was sampled and the solid concentration was measured, which was approximately 20 mass%. The particle size distribution of the solid content was measured using a laser scattering particle size analyzer, and the weight ratio of -10 μm particles to the total solid content was found to be nearly 100 mass%. Granulation tests were conducted on iron ore mixed raw materials under various conditions of this slurry concentration to confirm granulation properties, transportability, and sintering productivity. The natural settling method was used to change the slurry concentration, and the slurry was placed in a container and allowed to settle for a certain period of time, after which the supernatant water was removed and a slurry of the specified concentration was recovered.

[0019] First, the iron ore raw material mixture (moisture content 5.5maa%) was mixed and granulated in a drum mixer to obtain pseudo-particles. At this time, water was added to achieve the appropriate granulation moisture content. A preliminary investigation revealed that the appropriate moisture value was 7.5 mass%, so the amount of water added was set so that the total moisture contained in the slurry and the water added separately would be 7.5 mass%. A spray nozzle, pump, and piping were used to add the moisture. The ore raw material was placed into the drum mixer, and water and slurry were added at the same time the mixer started rotating. The total granulation time was 5 minutes.

[0020] Next, the pseudo-particles were placed in a small iron sintering test pot with a diameter of 300 mm and a height of 600 mm, and the raw material above the packed bed was ignited to conduct a sintering test. The sintered cake was dropped once from a height of 2 m, and the +10 mm ratio in the cake after the drop was defined as the product ratio. Productivity was calculated using the time required for sintering and the grate area of ​​the sintering machine tester.

[0021] Following the above-described process, comparisons were made between invention examples 1 to 10 and comparative examples 1 to 3 in terms of slurry transportability, mixing ability in a drum mixer, and sintering productivity, as shown in Table 1 below. In invention example 1, the collected slurry was used as is. In invention examples 2 to 8, the collected slurry was thickened to a concentration of 20 to 55 mass%. In invention examples 9 and 10, the collected slurry was thickened to a concentration of 20 to 55 mass%, and some of the added water was replaced with sinter. In comparative example 1, the slurry was completely dried and used as a powder. In comparative examples 2 and 3, the collected slurry was thickened to a concentration of 15 mass% and 60 mass%, respectively.

[0022] The slurry transportability was evaluated by measuring the clogging of the pipes when adding the slurry to the mixer. The mixing ability in the drum mixer was evaluated by measuring the clogging of the nozzle. The productivity was evaluated by a pot test.

[0023] [Table 1]

[0024] The results in Table 1 reveal the following. Comparative Example 1, which shows the results when the slurry was completely dried and used as a powder, demonstrated excellent transportability. However, because the powder was ultrafine, it absorbed moisture and agglomerated in the drum mixer, preventing the moisture from reaching the other ore raw materials, resulting in the formation of a large amount of ungranulated powder. Comparative Example 2, which shows the results when the collected slurry was diluted to a concentration of 15 mass%, demonstrated excellent transportability and mixability, but the productivity was not significantly different from that of Comparative Example 1. This is likely due to the low fine powder ratio in the charged raw materials (0.5 mass%), which did not demonstrate a clear binder effect. Comparative Example 3, which shows the results when the collected slurry was concentrated to a concentration of 60 mass%, demonstrated a rapid increase in the viscosity of the slurry, resulting in sludge, which made piping and nozzle injection difficult. As a result, the sludge could not be uniformly mixed with the raw materials, resulting in the formation of ungranulated powder and coarse particles, and reduced sinter productivity.

[0025] On the other hand, in Example 1, which shows the results when the collected slurry was used as is, the productivity was improved compared to Comparative Examples 1 and 2. In Examples 2 to 10, which show the results when the collected slurry was thickened to a concentration of 20 to 55 mass%, the sintering productivity improved as the fine powder ratio in the charged raw materials increased. Furthermore, comparing Examples 2 to 10, Examples 7 and 10 did not exhibit any problems with the transportability of the thickened slurry, but phenomena such as clogging were observed when sprayed from the nozzle. As a result, compared to Example 6, the slurry was not sprayed uniformly in the drum mixer, resulting in the generation of ungranulated powder and a slight decrease in productivity. In Example 8, the viscosity of the slurry increased, resulting in phenomena such as clogging when transported by the pump and when sprayed from the nozzle. As a result, compared to Example 7, the slurry was not sprayed uniformly in the drum mixer, resulting in the generation of ungranulated powder and a slight decrease in productivity.

[0026] From the above study, by comparing Examples 1 to 10 with Comparative Examples 1 to 3, it was found that 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 mass% enables highly productive sintered ore to be obtained without the need for a process of grinding iron ore into fine powder or an expensive anionic polymer dispersant. Furthermore, considering differences in the properties of dust particles, it was found that a more preferable range for the solid dust in the dust slurry solution is 30 to 50 mass%, and even more preferably 35 to 45 mass%.

[0027] <Example 2> As a suitable example, 10 mass% of high-grade, hematite-based fine ore (concentrate), which is difficult to granulate, was added to the sintering raw materials (45 mass% Australian ore, 45 mass% South American ore), and the effect of adding thickened slurry was confirmed. High-grade fine ore has a higher specific gravity than normal raw materials and is lacking in fine particles that contribute to adhesion. It has a narrow particle size distribution and high water permeability, but poor adhesion. Therefore, if a slurry is not used, as in conventional methods, the ore is prone to peeling during the rolling process inside the drum mixer, resulting in the problem of ungranulated powder.

[0028] Therefore, as in Example 10 of the present invention, a slurry with an initial concentration of 20 mass% was concentrated, and a slurry with a concentration of 40 mass% was added and granulated, and then a sintering test was conducted to determine the productivity, as in Example 9 of the present invention. As Comparative Example 5, a slurry with a concentration of 15 mass% was used, and a sintering test was conducted in the same manner as in Example 10 of the present invention to determine the productivity. The results are shown in Table 3 below. The results in Table 3 show that in Example 10 of the present invention, the pseudo-particle size was increased compared to Comparative Example 5, and the productivity was improved due to the effect of shortening the firing time.

[0029] [Table 2] Industrial application fields

[0030] According to the method for producing sintered ore of the present invention, by replacing part or all of the water added during granulation with a dust slurry solution in which solid dust is suspended in water at a concentration of 20 to 55 mass%, the granulation of sintered raw materials can be significantly improved, and this production method can be applied to various sintered raw materials in addition to the example.

Claims

1. A method for producing sintered ore, in which a sintering blend raw material containing iron ore of multiple brands and hematite-based ore is granulated together with added water in a granulator, and the resulting granulated raw material for sintering is fired in a sintering machine to obtain sintered ore, is characterized in that part or all of the added water used 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 mass %.

2. 2. The method for producing sintered ore according to claim 1, wherein the solid dust is generated in an iron-making process and contains 50 mass % or more of particles with a particle size of −10 μm.

3. 3. The method for producing sintered ore according to claim 1, wherein the solid dust concentration is increased to 30 to 50 mass%.

4. 3. The method for producing sintered ore according to claim 1, wherein the solid dust concentration is increased to 35 to 45 mass%.

5. 4. The method for producing sintered ore according to claim 3, wherein the method for increasing the solid dust concentration is by thickening using a thickener.

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