JP6380762B2 - Method for producing sintered ore - Google Patents

Description

  The present invention relates to a method for producing sintered ore as a blast furnace raw material, which is produced by using a DL-type sintering machine after granulation for a sintered raw material.

  Sintered ore consists of several brands of fine iron ore (generally called sinter feed of about 125 to 1000 μm), auxiliary raw material powders such as limestone, quartzite, and serpentine, and dust, scale, return ore, etc. The raw material powder and solid fuel such as powdered coke are mixed in an appropriate amount to add the moisture, mix and granulate, and charge the resulting granulated material into the sintering machine. Manufactured by firing. Generally, the sintered blending raw material contains moisture, and aggregates into pseudo particles during granulation. This pseudo-granulated raw material for sintering, when placed on the pallet of the sintering machine, helps to ensure good ventilation of the sintered raw material charging layer and facilitates the sintering reaction. Proceed to

By the way, in recent years, powder iron ore for sintering has been lowered in quality by depletion of high-quality iron ore. That is, the lower grade of iron ore leads to an increase in slag components and a tendency to pulverization, and therefore the granulation properties are decreased due to an increase in the alumina content and an increase in the pulverization ratio. On the other hand, sintered ore used in the blast furnace is required to have a low slag ratio, high reducibility, and high strength from the viewpoint of reducing hot metal production cost in the blast furnace and reducing CO ₂ generation amount. .

  In such an environment surrounding powdered iron ore for sintering, high-quality sintered ore is produced using the hardly granulated fine iron ore that has been used for pellets recently called pellet feed. Techniques for this have been proposed. For example, one such conventional technique is the Hybrid Pelletized Sinter method (hereinafter referred to as “HPS method”). In this technology, low-slag-ratio, highly-reducible sintered ore is produced by granulating a sintering compounded raw material containing a large amount of fine iron ore such as pellet feed using a drum mixer and pelletizer. (Patent Literature 1, Patent Literature 2, Patent Literature 3, Patent Literature 4, Patent Literature 5).

  In addition, prior to the sintering raw material powder granulation step, a method of conditioning and mixing with a high-speed rotary mixer (Patent Document 6), and before the granulation step, fine iron ore and iron dust are preliminarily mixed with a stirring mixer. A method of mixing (Patent Document 7), a method of premixing fine powder (pellet feed) with an Eirich mixer and then granulating with a drum mixer (Patent Document 8), containing 60% by weight or more of particles having a particle size of 250 μm or less There is also a proposal such as a method (Patent Document 9) in which an iron ore raw material is kneaded and then granulated with a drum mixer.

Japanese Patent Publication No.2-4658 Japanese Examined Patent Publication No. 6-21297 Japanese Examined Patent Publication No. 6-21298 Japanese Patent Publication No. 6-21299 Japanese Examined Patent Publication No. 6-60358 JP-A-60-52534 JP-A-1-312036 JP-A-7-331342 JP 2001-247020 A

  However, the sintered blending raw material containing a large amount of fine iron ore, particularly ultra fine iron ore, such as pellet feed, is granulated using the HPS method as described in Patent Documents 1 to 5, In the method of performing the mixing process in advance using a high-speed stirrer as described in Patent Documents 6 to 9, there are the following problems.

  That is, as shown in FIG. 1, in these methods, not only fine particles (less than 0.5 mm) but also large (greater than 10 mm) pseudo particles are generated. The reason is that fine iron ore like pellet feed, if the wettability is the same, the finer the specific surface area, the greater the specific surface area, so it is easy to absorb moisture and hold more moisture between the powders. It is because each fine iron ore becomes easy to absorb moisture preferentially. As a result, it is easy to generate coarse pseudo particles in which the fine particles are simply aggregated or coarse particles having irregular particle sizes in a form in which the fine particles adhere around the core particles. Furthermore, these methods also have problems of adhesion of powder, poor uniform dispersion of fine powder and moisture, and a decrease in equipment operation rate.

  This point is also clear from the following experiment conducted by the inventors. First, in this experiment, granulation was performed using a blended raw material containing finely granulated iron ore (vanadium content: 40 mass%) such as pellet feed, and at this time, the generated granulated particles (pseudo particles) ) And the particle size distribution of the pellet feed. The result is shown in FIG. First, as shown in FIG. 2 (a), those containing a large amount of pellet feed in the sintered blending material have a higher proportion of coarse particles (over 8 mm) than those containing no pellet feed. . The weight ratio reached about 75 mass%. In addition, the particle size distribution of the pellet feed in the granulated pseudo particles (FIG. 2B) showed the same tendency as the particle size distribution of the granulated particles (FIG. 2A). That is, the ratio of the pellet feed in the coarse grains was as high as about 80 mass%, and it was found that most of the pellet feed was unevenly distributed in the coarse grains. From this, it can be seen that coarse pseudo-particles are formed by aggregation of pellet feeds. And it turned out that this pseudo particle which belongs to a coarse-grain area | region also has a high moisture content (FIG.2 (b)). Therefore, the pellet feed is preferentially absorbed by the pellet feed, and therefore the pellet feeds aggregate to form coarse pseudo particles, and as a result, a large amount of moisture is absorbed in the coarse pseudo particles. It will be.

  In this way, the blended raw material containing a large amount of fine iron ore such as pellet feed, when granulated, inevitably becomes uneven in particle size, and the fine powder is merely agglomerated, and the bond strength is weak. Coarse pseudo particles are easily generated. Therefore, when such pseudo particles are charged and deposited on the pallet of the sintering machine, as shown in FIG. 3 (a), the sintered raw material charging layer has a dense deposition structure and a bulk density. Becomes larger. Moreover, if such coarse pseudo-particles are deposited on a pallet of a sintering machine with a certain layer thickness, they are easily broken when a load (compressive force) is applied to the pseudo-particles. This leads to a decrease in porosity, which in turn causes deterioration in air permeability, which becomes an impediment to sintering machine operation. As a result, the sintering time becomes longer, and the yield of sintered ore may be reduced, leading to a decrease in productivity. Furthermore, the amount of quicklime, which is a binder used for granulation, must be increased, resulting in an increase in the production cost of sintered ore, and sintering when coating solid fuel such as powdered coke in the subsequent process. As a result, non-uniformity of the existing state of the powdered coke and the like as the whole raw material is caused. As a result, combustion and poor heat receiving are caused and the firing rate is lowered.

  The object of the present invention is to use a fine ore as a raw material for the production of sintered ore, granulate appropriate pseudo particles, and improve the productivity of the sintered ore. It is to propose a manufacturing method.

  As a result of intensive investigations on the problems of the prior art described above, the inventors have previously processed a granulated raw material having a predetermined amount of fine powder having a predetermined particle size by a high-speed agitator, and thereafter granulated. Sometimes it is possible to prevent the generation of coarse granulated particles (pseudo particles) with uneven particle size and weak bond strength, and to improve the productivity in the sintering machine by granulating appropriate pseudo particles. The present invention was developed after finding out what can be done.

  That is, the present invention relates to a method for producing sintered ore in which a sintered raw material is obtained by granulating a sintered raw material after sintering with a sintering machine, and containing 10 to 50 mass% of fine iron ore of 125 μm or less. In the method for producing a sintered ore, the pretreatment is performed with a high-speed agitator and then granulated with a granulator.

In the method of manufacturing a sintered ore according to the present invention configured as described above,
(1) With respect to the peripheral speed U (m / s) of the blades of the high-speed stirring device, when the stirring time t (seconds) by the high-speed stirring device is used, the condition of 300 <U × t <2000 is satisfied. Pre-processing,
(2) The condition of 400 <U × t <1200 is satisfied when the stirring time t (seconds) by the high-speed stirrer is set with respect to the peripheral speed U (m / s) of the blades of the high-speed stirrer. Pre-processing,
(3) the granulator is a drum mixer and / or a disk pelletizer;
(4) In the granulation of the granulator, the treated raw material is coated with limestone, and the surface of the granulated particles is coated with a solid fuel,
(5) As the sintering raw material, at least one kind contains crystal water ore, and the content of crystal water is 4 mass% or more,
(6) containing 5 mass% or more of limestone in the fine iron ore of 125 μm or less,
(7) In addition to the lime content to be coated, slaked lime or quicklime is added in an amount of 3 mass% or less to the sintered raw material to be processed with the high-speed stirrer.
(8) In the sintering raw material used for the high-speed stirrer, when the proportion of fine iron ore is 30 mass% or more, the raw material is dried.
Is considered to be a more preferable solution.

  In the present invention, fine iron ore and fine particles are agglomerated firmly, or a structure in which fine iron ore or the like is adhered around the core particles is a sintered particle composed of pseudo particles having a relatively uniform particle size and a small particle size distribution. The manufacturing method of the granulation raw material for ligation is proposed. When the granulated raw material for sintering obtained by such a method is placed on a pallet of a sintering machine, the density of the sintered raw material charging layer formed on the pallet is reduced and the air permeability is improved. Thus, the firing time can be shortened, which is effective in improving the productivity of high-quality sintered ore.

It is a comparison graph of the particle size distribution of the pseudo particle in the presence or absence of fine iron ore blending. It is a graph which shows the distribution of the pellet feed for every particle diameter of pseudo | simulated (granulation) particle | grains, and the dispersion | distribution condition of a water | moisture content. It is a comparison figure of the conventional granulated particle deposition layer (a) and the granulated particle deposition layer (b) of the present invention. It is a figure for demonstrating an example of the equipment row | line | column which implements the manufacturing method of the sintered ore of this invention. It is a figure for demonstrating the equipment row | line | column used in order to investigate the influence of the pre-processing before granulation. It is a graph which shows the relationship between a harmonic average diameter and additional mixing time. It is a graph which shows the relationship between a particle size distribution function and additional mixing time. It is a graph which shows the relationship between a calculation production rate and additional mixing time. The peripheral speed U is a graph showing the relationship U = a 9m / s condition fixedly stirring time of t and production rate when changing the range of t = 0 to 240 seconds and (U × t). Stirring time t to t = 120 seconds condition circumferential speed is fixed to U of a graph showing the relationship between the production rate when changing the range of U = 0~18m / s and (U × t). The peripheral speed U is a graph showing the relationship U = a 9m / s condition fixedly stirring time of t and production rate when changing the range of t = 0 to 240 seconds and (U × t). It is a graph showing the distribution state showing the relationship between the (U × t) and the production rate in the case of the U <8m / s and U ≧ 8m / s.

<About pretreatment before granulation which is a feature of the present invention>
FIG. 4 is a diagram for explaining an example of an equipment row for carrying out the method for producing a sintered ore according to the present invention. The method for producing a sintered ore according to the present invention will be described with reference to FIG. 4. First, a sintering raw material 11 containing 10 to 50 mass% of fine iron ore of 125 μm or less is prepared. Sintering raw material 11 includes the above-mentioned 10-50 mass% of pellet feed of 125 μm or less and fine iron ore that is tailing ore, and fine iron ore with the balance being cinder feed, as well as returned ore, quartzite, lime, quicklime, etc. It is preferable to consist of other raw materials. In the present invention, the reason for limiting the sintered raw material 11 to those containing 10 to 50 mass% of fine iron ore of 125 μm or less is as follows.

  That is, the invention range of the fine iron ore is set to produce coarse particles with irregular particle sizes and weak bond strength. If it is less than 10%, pseudo particles with low bond strength cannot be formed, and 50%. If exceeding the above, there is a problem that coarse particles having a weak bond strength can be formed in the same manner. However, the upper limit is set to 50% without adding more than 50 mass% of fine iron ore of 125 μm or less. The reason why the particle size is set to 125 μm or less is that when the particle size is 125 μm or less, the adhesion force representing the adhesion between the particle layers in the powder-filled layer to which moisture has been added increases, and thus the granulation property is greatly different. Therefore, 125 μm was set as the particle size section.

  Next, pretreatment of the prepared sintered raw material 11 is performed with a high-speed stirrer 12. The purpose of the high-speed stirrer 12 is to break up agglomerates of fine powder, which are seeds of coarse granulated particles, before granulation in order to suppress the formation of coarse granulated particles. From the microscopic viewpoint, it is effective to exfoliate the fine powder directly by applying a shearing force to the aggregate itself in order to efficiently break the fine powder aggregate. As an example of the high-speed stirrer 12, for example, an Eirich mixer (manufactured by Nihon Eirich), a Pelegaia mixer (manufactured by Kitagawa Tekko), a pro-shear mixer (Pacific Kiko) can be used. Among these, the Eirich mixer is known as a “high-speed agitation granulation” machine, and is a facility that also has a granulation function accompanying the aggregation and growth of particles by liquid crosslinking.

  Next, the sintered raw material 11 that has been subjected to the pretreatment with the high-speed stirrer 12 is stirred and mixed by the drum mixer 13 with the addition of moisture, and granulated. The sintered raw material 11 after granulation is supplied to a sintering machine 14 and becomes a sintered ore in the sintering machine 14. The sintered ore is supplied to the blast furnace 15 as a blast furnace raw material together with coke and limestone to produce pig iron.

  In order to investigate the influence of pretreatment before granulation, which is a feature of the present invention, as shown in FIG. 5, a high-speed stirring mixer (Eirich mixer) is used for the same sintered raw material containing 30 mass% of 125 μm fine iron ore. And a drum mixer were used for pretreatment before granulation. The mixing time by each mixer is changed from 0 to 160 seconds, the particle size distribution is obtained for the sintered raw material after granulation for 160 seconds by the drum mixer after the pretreatment, and Is defined by the following formula based on it. , Ip, and the harmonic mean diameter Dp (mm), the particle size distribution function Isp, and the relative passing air volume of the packed bed before sintering are shown in FIG. 6, FIG. 7, and FIG. In any of the examples, an example in which the pre-processing by the drum mixer is 0 seconds is a conventional example. The harmonic average diameter was increased by using it in a high-speed stirring mixer, and the effect of sharpening the particle size distribution by the particle size distribution function Isp was obtained. The effect of increasing relative currency volume was also obtained. Here, the larger the relative passing air volume, the larger the value, the higher the gas volume in the sintering machine operating at a constant negative pressure, and the higher the productivity.

Dp = 1 / Σ (wi / di)
Isp = 100√ (Is × Ip)
Is = Dp ² Σwi (1 / di−1 / Dp) ²
Ip = (1 / Dp) ² Σwi (di−Dp) ²
here,
Dp: harmonic mean diameter (mm)
wi: Weight abundance ratio in the section (−)
di: Typical average diameter of the section (mm)
Isp: particle size distribution function Is: particle size distribution function in fine particles (-)
Ip: Particle size distribution function (−) in coarse particles

  From the results of FIGS. 6, 7 and 8, the example of the present invention in which the pretreatment before granulation was performed with a high-speed stirring mixer was performed in the conventional example in which the pretreatment was not performed and the pretreatment before granulation was performed with a drum mixer. Compared with the comparative example, a high harmonic mean diameter (Fig. 6), a low particle size distribution function (Fig. 7) and a high relative passing air volume (Fig. 8) of the packed bed before sintering can be obtained. It was found that a ligation raw material was obtained.

<Suitable operating conditions for high-speed agitator>
In order to investigate suitable operating conditions of the high-speed stirrer in the method for producing sintered ore of the present invention, the peripheral speed of the blade rotating at a high speed of the high-speed stirrer with respect to the same sintered raw material containing 30 mass% of 125 μm fine iron ore Attention was paid to the relationship between U (m / s) and stirring time t (seconds). The example in which the circumferential speed U is fixed to the condition of U = 9 m / s and the stirring time t is changed in the range of t = 0 to 240 seconds, and the stirring time t is fixed to the condition of t = 120 seconds and the circumferential speed U is fixed. Regarding an example in which the speed U is changed in the range of U = 0 to 18 m / s, and an example in which the peripheral speed U is fixed to the condition of U = 6 m / s and the stirring time is changed in the range of 0 to 240 seconds. After the granulation, the production rate of the sintered ore obtained by sintering with a sintering machine was obtained, and the production rate was arranged by (U × t).

Here, as a condition for preventing generation of coarse granulated particles (pseudoparticles) having uneven particle sizes and weak bond strength, it is possible to granulate appropriate pseudoparticles at a circumferential speed U at a stirring time t. We focused on U x t multiplied by. The dimension of U × t has a physical quantity with a dimension of “m” in length, and is considered to be a moving distance given by a blade rotating at high speed. Therefore, it can be arranged by different peripheral speeds and stirring times. It was. In the high-speed stirrer, since the raw material charged from the upper part flows out to the lower part, the stirring time changes when the raw material occupancy in the apparatus is constant or the charging speed is changed. At that time, it can be seen that stable sintered ore quality by determining an appropriate range U × t becomes possible to produce.

The production rate (t / hr / m ² ) and (U × t) when the circumferential speed U is fixed to U = 9 m / s and the stirring time t is changed in the range of t = 0 to 240 seconds. 9 and Table 1 below, the production rate (t / hr) when the stirring time t is fixed at t = 120 seconds and the peripheral speed U is changed in the range of U = 0 to 18 m / s. / M ² ) and (U × t) are shown in FIG. 10 and Table 2 below, and the circumferential speed U is fixed at U = 6 m / s and the stirring time t is t = 0 to 240 seconds. The relationship between the production rate (t / hr / m ² ) and (U × t) when changed in the range is shown in FIG. 11 and Table 3 below.

From the results of FIGS. 9 to 11 (based on the data in Tables 1 to 3), the relationship between (U × t) and the production rate is obtained for two conditions of U <8 m / s and U ≧ 8 m / s. 12 shows a scatter diagram. From the results of FIG. 12, in each of the examples, it is preferable to perform the pre-processing by a high-speed stirrer to meet U × t a 300 <U × t <2000 conditions, 400 U × t <U × t < It can be seen that it is more preferable to perform pretreatment with a high-speed stirrer so as to satisfy the condition of 1200. Since the preferable range of U × t is almost the same in any of the examples, it can be understood that the range of U × t can be generalized as a preferable example for various examples of the peripheral speed and the stirring time of the high-speed stirrer. .

  Moreover, from the result of FIG. 9, in the pre-processing of the sintering raw material performed by the high-speed stirring device, when the peripheral speed U of the blade rotating at high speed of the high-speed stirring device is 9 (m / s), the stirring of the high-speed stirring device It can be seen that the time is preferably 30 seconds or more. Furthermore, from the result of FIG. 10, when the stirring time of the high-speed stirring device is 120 seconds, it is preferable that the peripheral speed U (m / s) of the blade rotating at high speed of the high-speed stirring device is 6 ≦ U ≦ 12. I understand that. Furthermore, from the result of FIG. 11, when the peripheral speed U of the blade rotating at high speed of the high-speed stirrer is 6 (m / s) in the pretreatment of the sintering raw material performed by the high-speed stirrer, It can be seen that the stirring time is preferably 60 seconds or more.

<Other suitable operating conditions>
In the method for producing sintered ore of the present invention, a disk pelletizer can be used alone or in combination with a drum mixer, in addition to the drum mixer as a granulating apparatus in the above-described embodiments.

  In the granulation of the granulator, it is preferable to coat the raw material that has been treated with limestone and to coat the surface of the granulated particles with a solid fuel. It is preferable to make the exterior to make calcium ferrite with high strength on the surface by making limestone exterior, and to adhere to the surface because it has a negative effect on granulation due to the hydrophobic nature of the solid fuel. This is because the productivity is improved by increasing the granulated particle diameter.

  Furthermore, as the sintering raw material, it is preferable to use one containing at least one kind of crystal water ore and a crystal water content of 4 mass% or more. The reason why the content of crystallization water is preferably 4 mass% or more is because an ore having a high crystallization water has a high specific surface area and can improve the granulation property of fine ore. Furthermore, it is preferable that 5 mass% or more of limestone is contained in the fine iron ore of 125 μm or less. It is preferable that 5 mass% or more of limestone is contained. By containing fine limestone, the mixing property of fine ore and limestone can be improved, and the sintering reaction can be promoted.

  Moreover, it is preferable to add 3 mass% or less of slaked lime or quicklime to the sintering raw material processed with a high-speed stirrer in addition to the lime content to coat. It is preferable to add slaked lime or quicklime to 3 mass% or less because the addition of slaked lime or quicklime can improve the crushing strength of the granulated particles and improve the air permeability in the sintered raw material packed layer. . Furthermore, in the sintering raw material used for the high-speed stirrer, it is preferable that the sintering raw material is subjected to a drying treatment when the proportion of fine iron ore is 30 mass% or more. It is preferable to perform the drying process at 30 mass% or more because the moisture in the sintering process needs latent heat to evaporate, and the carbonaceous materials such as powdered coke can be reduced by drying in advance. It is.

  According to the method for producing sintered ore of the present invention, high-quality sintered ore can be produced with high productivity using various sintering machines, and the sintered ore obtained in the present invention as a blast furnace raw material. By using this, it becomes possible to perform blast furnace operation with high productivity.

Claims (8)

In the method for producing sintered ore, the sintered raw material is sintered by a sintering machine after granulation, and the sintered raw material containing 10 to 50 mass% of fine iron ore of 125 μm or less is preliminarily processed at high speed. Then, when granulating with a granulating apparatus, the pretreated sintered raw material is coated with limestone, and the surface of the granulated particles is coated with a solid fuel. A method for producing sintered ore.   Pre-processing so as to satisfy the condition of 300 <U × t <2000 when the stirring time t (second) by the high-speed stirrer is set with respect to the peripheral speed U (m / s) of the blades of the high-speed stirrer The method for producing a sintered ore according to claim 1, wherein:   Pre-processing so as to satisfy the condition of 400 <U × t <1200 when the stirring speed t (seconds) by the high-speed stirring device is set to the peripheral speed U (m / s) of the blades of the high-speed stirring device. The method for producing a sintered ore according to claim 2, wherein:   The method for producing a sintered ore according to any one of claims 1 to 3, wherein the granulator is a drum mixer and / or a disk pelletizer. The sintered ore according to any one of claims 1 to 4 , wherein the sintered raw material includes at least one kind of crystal water ore, and a content of crystal water is 4 mass% or more. Manufacturing method. The sinter ore manufacturing method according to any one of claims 1 to 5 , wherein the fine iron ore of 125 µm or less contains 5 mass% or more of limestone. The sintered ore according to any one of claims 1 to 6 , wherein slaked lime or quicklime is added in an amount of 3 mass% or less in addition to the lime content to be coated to the sintered raw material to be processed by the high-speed stirring device. Manufacturing method. In the sintering raw material used in the high-speed stirring device, the proportion of iron ore fines of sintered ore according to any one of claims 1 to 7, wherein the drying process of the raw material in the above 30 mass% Production method.

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