Method for producing granulation raw material for sintering and method for producing sintered ore

Abstract

The present invention addresses the problem of providing a method for improving the manufacturability of sintered ore by using a granulation raw material obtained by this method, which is used for the establishment of a more advanced production technique for a granulation raw material for sintering, by studying the suitability of stirring conditions (stirring energy) that take into account the properties of iron ore that fluctuates (micronization, and the like). The present invention also addresses the problem of providing a method for improving the manufacturability of sintered ore by using the granulation raw material obtained by this method. A method for producing a granulation raw material for sintering, characterized in that when the granulation raw material for sintering is produced by granulating after stirring a raw material for sintering at a high speed, the stirring power during the high-speed stirring is adjusted in accordance with the particle size distribution of an iron-containing raw material in the raw material for sintering.

Description

Technical Field

[0001] The present invention relates to a method for producing a granulated raw material for sintering used in a DL type sintering machine or the like, and a method for producing a sintered ore using the method. Background Art

[0002] Sintered ore is produced by mixing appropriate amounts of auxiliary raw material powders such as limestone, silica, serpentine, dust, scale, return ore, and solid fuels such as powdered coke with various types of powdered iron ore (generally materials of about 125 to 1000 μm, which are called sinter feed) to form a sintering feed, adding water to the sintering feed, mixing, and granulating, and loading the obtained granulated feed into a sintering machine for sintering.

[0003] Generally speaking, the sintering raw materials contain water so that they aggregate with each other during granulation and become quasi-particles. In addition, it is known that when the quasi-particleized sintering granulation raw material is loaded on the pallet of the DL sintering machine, it helps to ensure good ventilation of the sintering raw material loading layer, so that the sintering reaction proceeds smoothly. During the sintering reaction, the water content of the heated granulation raw material particles evaporates, and the granulation raw material particles downwind become high in water content, forming an area (wetting zone) with reduced strength. In addition, in this wetting zone, the particles of the granulation raw material are easily broken and hinder the flow in the raw material filling layer, which deteriorates the air permeability.

[0004] On the other hand, it is known that in recent years, the micronization of iron ore has been continuously promoted, and the strength of granulated particles produced using micronized iron ore is relatively low. In particular, when water is added to micronized iron ore, the strength decreases significantly, which becomes a cause of decreased air permeability. In addition, micronized iron ore sometimes becomes difficult to granulate in the manufacture of granulated raw materials for sintering. In the environment surrounding iron ore powder for sintering, a technology for producing high-quality sintered ore using iron ore that is difficult to granulate and contains a large amount of micropowder has recently been proposed.

[0005] For example, as one of the prior arts, there is the HPS method (Hybrid Pelletized Sinter method) described in Patent Document 1. This technology intends to granulate fine powder iron ore with a high iron content using a drum mixer and a granulator, thereby producing a low slag ratio and high reducibility burnt agglomerate ore. However, in this technology, there is the following problem: when granulating fine powder iron ore in large quantities, many granulators need to be installed, which increases the manufacturing cost.

[0006] Next, the following method was proposed: before the granulation process of the sintering raw material powder, the raw material containing fine powder iron ore is pre-treated or granulated using a high-speed rotating mixer. That is, the following method was proposed: before the granulation process, the fine powder iron ore and ironmaking dust are pre-mixed with a stirring mixer, and then granulated with the stirring mixer; the method of stirring the sintering raw material mainly composed of fine powder with a stirrer and then granulating with a granulator (Patent Documents 2 to 3). However, in these methods, there are the following problems: the granulated particles are mainly composed of fine powder raw materials, and the strength of the granulated particles is reduced compared with the case of using core particles (iron ore) with higher strength than the granulated particles.

[0007] Next, a method was proposed in which a sintering raw material containing fine powder and sintering raw material is mixed in advance with an Eirich mixer, and then granulated with a drum mixer (Patent Documents 4 to 6). However, in these methods, there is a concern that when the proportion of fine powder increases, the attached powder layer becomes excessive, and the combustibility of the granulated particles deteriorates. In addition, there is also the following problem: due to insufficient core particles, the granulation property deteriorates, and the sintering is performed in an incomplete granulation state.

[0008] Next, a technology for treating a difficult-to-granulate ore containing fine powder and a large amount of crystal water was proposed (Patent Documents 7 to 9). However, in these prior arts, there is a problem that it is difficult to prevent the pressure loss in the wet zone from increasing due to the evaporation of a large amount of water from the highly crystalline ore during the sintering process. Moreover, in these methods, there is also a problem that when using a large amount of fine powder iron ore, the strength of the granulated particles tends to decrease, and the pressure loss in the wet zone tends to increase further.

[0009] In addition, regarding the use of high-speed stirring when using fine powder, a granulation method that takes into account stirring conditions, device size, and ore properties such as core ore (Patent Documents 10 and 11) has been proposed. However, the solutions disclosed in these documents do not actually achieve research on stirring conditions that match ore properties.

[0010] Prior art literature

[0011] Patent Literature

[0012] Patent Document 1: Japanese Patent Application Laid-Open No. 62-37325

[0013] Patent Document 2: Japanese Patent Application Laid-Open No. 1-312036

[0014] Patent Document 3: Japanese Patent Application Publication No. 2007-247020

[0015] Patent Document 4: Japanese Patent Application Laid-Open No. 11-061282

[0016] Patent Document 5: Japanese Patent Application Laid-Open No. 7-331342

[0017] Patent Document 6: Japanese Patent Application Laid-Open No. 7-48634

[0018] Patent Document 7: Japanese Patent Application Publication No. 2005-194616

[0019] Patent Document 8: Japanese Patent Application Publication No. 2006-63350

[0020] Patent Document 9: Japanese Patent Application Publication No. 2003-129139

[0021] Patent Document 10: International Publication No. 2017 / 094255

[0022] Patent Document 11: International Publication No. 2017 / 150428 Summary of the invention

[0023] Problems to be solved by the invention

[0024] Therefore, the present invention aims to establish a technology that can overcome the problems of the above-mentioned prior art, and in particular, to propose a method for establishing a more advanced manufacturing technology for sintering granulated raw materials by studying the optimization of stirring conditions (agitation energy) obtained by taking into account the properties of iron ore that vary daily (micronization, etc.), and to improve the manufacturability of sintered ore by using granulated raw materials obtained by adopting this method.

[0025] Means for solving problems

[0026] During the diligent research on the problems of the above-mentioned prior art, the inventors focused on the properties of iron ore, especially the adhesion of the fine powder part, and repeatedly conducted research. As a result, in the case of iron ore with poor adhesion of the fine powder, the effect of high-speed stirring can be maximized by stirring more or not stirring. On the other hand, it was found that in the case of iron ore with low adhesion, it is effective to exert the effect of high-speed stirring by applying lower stirring energy. Here, the stirring energy cannot be estimated based on the circumferential speed of the blade or the length of the blade, but it is difficult to easily estimate the stirring energy because it changes according to mechanical conditions such as the moisture content related to the adhesion of the raw material, the height and position of the raw material collides with the blade or the type of mineral.

[0027] It is known that the problems of the prior art can be controlled by focusing on the particle size distribution index (SDI), which is an index obtained by taking into account the particle size distribution of the iron ore itself. Therefore, the energy applied when stirring the sintering raw materials is determined based on the index (SDI) to maximize the productivity of the sintering granulated raw materials and sintered ore.

[0028] That is, the present invention proposes a method for producing a granulated raw material for sintering, characterized in that when a sintering raw material is granulated after high-speed stirring to produce the granulated raw material for sintering, the stirring power during the high-speed stirring is adjusted according to the particle size distribution of the iron-containing raw material in the sintering raw material.

[0029] The present invention also provides a method for producing sintered ore, characterized in that the granulated raw material for sintering produced by the method for producing the granulated raw material for sintering is charged into a sintering machine for sintering.

[0030] It should be noted that, in the present invention, it is considered that if the following scheme is adopted, it will become a more preferred embodiment:

[0031] (1) During high-speed stirring of the sintering raw materials, the stirring power is adjusted based on the particle size distribution index (SDI) of the following formula (1);

[0032]

[0033] in,

[0034] W io500 (mass %) is the proportion of iron-containing raw materials not exceeding 500 μm,

[0035] W fL (mass %) is the proportion of particles with a particle size of 15 to 500 μm in the iron-containing raw material,

[0036] W fS (mass %) is the proportion of particles with a particle size of less than 15 μm in the iron-containing raw material,

[0037] d L (mm) is the average particle size of particles with a particle size of 15 to 500 μm in the iron-containing raw material,

[0038] d S (mm) is the average particle size of particles with a particle size of less than 15 μm in the iron-containing raw material.

[0039] (2) during the high-speed stirring of the sintering raw material, a sintering raw material having a particle size distribution index (SDI) satisfying the relationship of SDI>7 represented by the formula (1) is used;

[0040] (3) When the sintering raw material is stirred at high speed, stirring is performed at high speed with a stirring power satisfying the following formula (2),

[0041] 0.172×{1+(1.12SDI-8.95)}×Q>0…(2)

[0042] Here, Q (kWh / t) is the value obtained by dividing the difference in power consumption (kWh) of the rotor of the stirring blade between load and no load by the weight (t) of the sintering raw material to be stirred at high speed. (Load: with sintering raw material. No load: idling without sintering raw material).

[0043] Effects of the Invention

[0044] In the present invention, since high-speed stirring can be appropriately performed as a process before granulation, a more complete mixing state can be gradually approached, and the granulation property after so-called high-speed stirring can be improved. In addition, this can lead to an increase in the production of sintered ore. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 This is a graph showing the relationship between stirring energy and granulated particle size.

[0046] Figure 2 This is a graph showing the relationship between the granulated particle size and the sintering productivity.

[0047] Figure 3 It is a graph showing the relationship between the particle size distribution index and the influence coefficient.

[0048] Figure 4 This is a graph showing the relationship between the stirring energy and the increase value of the granulated particle size. DETAILED DESCRIPTION

[0049] First, the present inventors studied the physical properties of the attached powder layer in order to improve the effect of high-speed stirring as a treatment before granulation. As a result, in the case of poor adhesion of the attached powder, the attached powders that have already adhered to each other are peeled off due to high-speed stirring, and the subsequent granulation treatment requires more time. On the other hand, in the case of highly adherent attached powders, if they are in a completely mixed state, the adhesion is high and granulation is promoted, but in the case of unmixed, the particle size distribution is not optimized, and the particle size is difficult to grow during granulation, thus developing the present invention.

[0050] Hereinafter, an example conducted to confirm the effect of the present invention will be described. In the study using this example, first, a sintering raw material including an iron-containing raw material was stirred at high speed, then granulated using a drum mixer to obtain a granulated raw material for sintering, and then the granulated raw material was used to sinter using a DL sintering machine, and the resulting effect of improving the sintered ore productivity was studied.

[0051] The raw material mix at this time is shown in Table 1. In this test, the mix ratios of three varieties, namely, sintering raw material, ore C as concentrate, and ore D as pellet material, were changed and used as iron-containing raw materials. Tests were carried out to mix the basic mix and add ores C and D as fine powder concentrates, and to mix each fine powder concentrate to a standard of 15% by mass. Since ore D is a pellet material, it is very fine compared to ore C, and the effect of fine particles can be evaluated. It should be noted that here, as a fine powder iron-containing raw material, pellet material (ore D) is used, but dust generated in the iron-making process containing particles with a particle size of less than 15 μm, like pellet material (ore D), can also be used.

[0052] [Table 1]

[0053] Sample No. Case 1 Case 2 Case 3 Case 4 Sintering raw materials 78.0 73.4 65.0 65.0 Concentrate: Ore C 0.0 5.3 13.4 0.0 Pellet material: Ore D 0.0 0.0 0.0 13.4 dolomite 7.6 6.8 7.1 6.9 Rolling scale 1.9 2.2 2.2 2.2 limestone 11.5 11.1 10.6 10.9 quicklime 1.0 1.1 1.1 1.1 total 100.0 100.0 100.0 100.0 Coke 4.5 4.4 44 4.4

[0054] In this test, in order to evaluate the performance of the high-speed mixer, the change in the granulation particle size relative to the residence time (mixing time) in the high-speed mixer was investigated. It should be noted that since the mixer is used in a continuous operation, the residence time T (sec) is expressed as the input raw material amount M as shown in the following formula (3). f (t / sec) and stowage capacity M in (t) is determined by the ratio.

[0055]

[0056] In addition, in order to evaluate the stirring energy applied to the raw material to be stirred, the power consumption of the rotor of the stirring blade attached to the high-speed stirrer is measured. The power applied to the raw material is obtained by subtracting the value when no raw material is added (idling) from the power when it is added under various conditions, and the power consumption is calculated based on the power and the residence time of the above formula (3). The value obtained by dividing the power consumption by the loading amount is the power consumption applied to each unit of raw material, which is defined as the stirring energy per unit of raw material.

[0057] Figure 1 The relationship between the granulation particle size of ores C and D relative to the stirring energy per unit raw material in the actual machine mixer is shown. As shown in the figure, in the absence of fine powder concentrate, the granulation particle size increases by increasing the stirring energy. In addition, when the ore C as the concentrate is 5.3 mass%, the granulation particle size increases slightly by the high-speed stirring method, but when it is increased to 13.4 mass%, the granulation particle size decreases on the contrary. On the other hand, when the ore D as the pellet material is increased to 13.4 mass%, the granulation particle size increases significantly by the high-speed stirring method.

[0058] exist Figure 2 The figure shows the relationship between the granulation particle size and the sintering productivity when mixing fine powder concentrates in an actual machine test. As shown in the figure, it can be seen that even if the fine powder of either ore C or D is increased, the granulation particle size will become smaller and the sintering productivity will decrease in both the conventional method and the high-speed stirring method, compared with the case of granulating with 5.3% by mass of ore C as the basic condition (conventional method). On the other hand, if we focus on the effect of the pre-treatment produced by high-speed stirring, the sintering productivity is increased from 1.01t / h / m to 2.01t / h / m by high-speed stirring compared with the conventional method. 2 to 1.04t / h / m 2 Increased by 0.03t / h / m 2 When the ore C content was 13.4 mass%, the high-speed stirring method had little effect. On the other hand, when the ore D as a pellet material was added, the productivity increased from 0.92 t / h / m to 0.92 t / h / m by using the high-speed stirring method compared to the case without stirring. 2 To 0.99t / h / m 2 Increased by 0.07t / h / m 2 .

[0059] According to the above implementation results, although it can be considered that when fine-grained micro-powder concentrate is used in the actual machine sintering process, the decrease in sintering productivity accompanied by the decrease in granulation particle size is inevitable, but according to the above results, by introducing the high-speed stirring method according to the present invention, the decrease in granulation particle size can be suppressed and the sintering productivity can be improved.

[0060] Next, in order to quantitatively make the effect of the characteristic high-speed stirring in the method for producing the sintering granulated raw material of the present invention more obvious, the influence of the stirring energy on the increase in the granulation particle size was studied. As a result, under the conditions of the same type of fine powder concentrate and the addition ratio, the increase in the granulation particle size can be said to be the value obtained by subtracting the granulation particle size obtained by the conventional method from the granulation particle size obtained by the high-speed stirring method. Therefore, the increase in the granulation particle size caused by the high-speed stirring method when the fine powder concentrate is 0% by mass of the raw material was first evaluated. That is, the increase in the granulation particle size caused by the high-speed stirring method under the condition of 0% by mass of the fine powder concentrate is set to ΔD (Q) (mm), and the stirring energy is set to a function of Q (kWh / t). Then, according to Figure 1 When the relationship between Q and ΔD(Q) is calculated as a function, the following equation (4) can be obtained.

[0061] ΔD(Q)=0.172Q…(4)

[0062] In addition, in order to evaluate the type of micronized concentrate Figure 2 The following are the values ​​of increase in particle size ΔD under various conditions of fine powder concentrate type and addition amount.p When the influence coefficient α is defined according to formula (4) for each type of fine powder concentrate, the following formula (5) is obtained.

[0063] α=(ΔDp-ΔD(Q)) / ΔD(Q)…(5)

[0064] In addition, it can be considered that, with 15 μm as the boundary, ultrafine powders below this particle size improve the adhesion between ores, and particles above this particle size reduce the adhesion. (S. Kawachi, S. Kasama: Tetsu-to-Hagane, 94 (2008), 475.) Therefore, the proportion of iron ore that is considered to be adhesion powder and does not exceed 500 μm is used. io500 The percentage of particles with a particle size of 15 to 500 μm in the iron-containing raw material WfL (mass %), the percentage of particles with a particle size of not more than 15 μm WfL (mass %), fS (mass %), average particle size d of particles with a particle size of 15 to 500 μm L (μm), the average particle size of the particle size does not exceed 15μm S (μm), redefine the particle size distribution index (SDI).

[0065] Here, the average diameter of particles with a diameter of 15 to 500 μm is 87 μm, which is the geometric mean of 15 μm and 500 μm. For particles with a diameter of not more than 15 μm, 4 μm, which is the geometric mean of 1 μm and 15 μm, is used. It should be noted that in the following formula (6), the weight ratio of each particle is divided by the average particle diameter d L d S The reason for this is to reflect the influence of the specific surface area of ​​the particles which is believed to have an influence on the adhesion.

[0066]

[0067] It should be noted that, in the present invention, the particle size is the particle size obtained by sieving using a sieve with a nominal mesh size according to JIS (Japanese Industrial Standard) Z 8801-1. For example, a particle size of less than 1 mm refers to a particle size that is completely passed through a sieve with a nominal mesh size of 1 mm according to JIS Z 8801-1, and is hereinafter also referred to as -1 mm. In addition, the minimum value of the nominal mesh size specified in JIS (Japanese Industrial Standard) Z 8801-1 is 20 μm, and in the case of a smaller value, for example, less than 15 μm, it refers to a particle size with a cumulative fraction of less than 15 μm obtained by the laser diffraction / scattering method according to JIS Z8825 and the liquid phase gravity sedimentation method according to JIS Z8820-2 being substantially 100%.

[0068] Next, use Figure 2The data shown can be used to obtain the following equation (7) based on the analytical results obtained from the relationship between the influence coefficient α of equation (5) and the particle size distribution index SDI of equation (6). Figure 3 The relationship is shown in .

[0069] α=1.12.SDI-8.95…(7)

[0070] like Figure 3 As shown, it can be seen that there is an obvious positive correlation between the particle size distribution index SDI and the influence coefficient α. This situation shows that the larger the particle size distribution index SDI is, the greater the increase in the granulation particle size ΔD brought about by the high-speed stirring method. p The larger the particle size, the better. According to these results, in order to achieve an increase in the granulation particle size by high-speed stirring, it is effective to increase the proportion of particles not exceeding 15 μm in the fine powder concentrate and reduce the proportion of particles from 15 to 500 μm. It should be noted that as an effect of adding particles not exceeding 15 μm, it can be considered that since they are uniformly dispersed between the raw material particles during high-speed stirring, as a result, the effect of improving adhesion is exerted.

[0071] On the other hand, it is presumed that particles of 15 to 500 μm have low adhesion and cannot fix particles to each other, but rather have a function of hindering adhesion of particles to each other during granulation.

[0072] Next, when solving ΔD according to equations (5) and (7), p (increase value of granulated particle size), the following formula (8) can be obtained.

[0073] AD P =(1+α)·ΔD(Q)

[0074] =(1+(1.12SDI-8.95))·ΔD(Q)…(8)

[0075] then, Figure 4 The increase in particle size ΔD calculated using the particle size distribution index SDI and stirring energy Q as parameters is shown. p The results obtained are based on the impact of Figure 4 It can be seen that if the SDI is the same, the greater the stirring energy (kWh / t) applied to the raw material, the greater the increase in the granulation particle size ΔD p If the stirring energy is the same, the larger the SDI is, the greater the increase in the particle size ΔD will be. pTherefore, when the proportion of particles of 15 to 500 μm with reduced adhesion increases and SDI decreases, as in the case of a concentrate, a larger stirring energy is required to obtain the same particle size increase effect. On the contrary, when the proportion of particles not exceeding 15 μm increases and SDI increases, as in the case of a pellet material, the granulation improvement effect brought about by the high-speed stirring method can be obtained by applying a relatively small stirring energy.

[0076] According to the above results, when a large amount of fine powder ore is used in the manufacture of sintering granulation raw materials, it is important to preferentially mix a large amount of pellets and stir them at high speed in order to maintain granulation properties. This effect can be considered to be due to the fact that the pellets with the attached powder layer are mixed and strengthened, thereby improving the filling properties and the adhesion of the granulated particles.

[0077] Industrial Applicability

[0078] The present invention can be applied not only to granulated raw materials for sintering, but also as a technology for granulating and agglomerating other raw materials for iron and steel making.

Claims

1. A method for producing a granulated raw material for sintering, characterized in that: When a granulated raw material for sintering is produced by granulating a sintering raw material at a high speed after stirring the sintering raw material, the power during the high speed stirring is adjusted according to the particle size distribution of the iron-containing raw material in the sintering raw material.

2. The method for producing a granulated raw material for sintering according to claim 1, characterized in that: During high-speed stirring of the sintering raw materials, the stirring power is adjusted based on the particle size distribution index (SDI) of the following formula (1): in, W io500 (mass %) is the proportion of iron-containing raw materials not exceeding 500 μm, W fL (mass %) is the proportion of particles with a particle size of 15 to 500 μm in the iron-containing raw material, W fS (mass %) is the proportion of particles with a particle size of less than 15 μm in the iron-containing raw material, d L (mm) is the average particle size of particles with a particle size of 15 to 500 μm in the iron-containing raw material, d S (mm) is the average particle size of particles with a particle size of less than 15 μm in the iron-containing raw material.

3. The method for producing a granulated raw material for sintering according to claim 2, characterized in that: During the high-speed stirring of the sintering raw material, a sintering raw material having a particle size distribution index (SDI) expressed by the formula (1) satisfying the relationship of SDI>7 is used.

4. The method for producing a granulated raw material for sintering according to any one of claims 1 to 3, characterized in that: When the sintering raw materials are stirred at high speed, stirring is performed at high speed with a stirring power satisfying the following formula (2): 0.172×{1+(1.12SDI-8.95)}×Q>0…(2) Among them, Q (kWh / t) is the value obtained by dividing the difference in power consumption (kWh) of the rotor of the stirring blade between load and no-load by the weight (t) of the sintering raw materials subjected to high-speed stirring (load: with sintering raw materials; no-load: idling without sintering raw materials).

5. A method for producing sintered ore, characterized in that: The granulated raw material for sintering produced by the method for producing a granulated raw material for sintering according to claim 4 is charged into a sintering machine and sintered.

Images