Design method of granulation process of iron ore and raw material processing method using the same

Abstract

To provide a design method of a granulation process of iron ore capable of efficiently performing optimum granulation in accordance to characteristics of iron ore, without necessitating trial and error.MEANS FOR SOLVING THE PROBLEM: The present invention provides a method for designing a granulation process for iron ore, comprising the steps of: determining a condition range that is the range of adhesiveness and fluidity of the granulation process; measuring the adhesiveness and fluidity of the iron ore to be granulated; and selecting a granulation process whose condition range includes the measured values of adhesiveness and fluidity of the iron ore to be granulated.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for designing a process for granulating powdered iron ore and fine ore (hereinafter collectively referred to as "iron ore"), which are raw materials to be granulated, and a method for using the same to process the raw materials to be granulated so that they are compatible with existing granulation processes. [Background technology]

[0002] In the blast furnace steelmaking process, sintered ore is the main raw material. Sintered ore is made by firing raw materials in a sintering machine. Sintered raw materials consist mainly of fine ore and auxiliary materials. Most of this is iron ore with a particle size of 10 mm or less. The remainder is auxiliary materials, miscellaneous materials, and coke. The average particle size of iron ore is usually 2.0-3.0 mm, and the particle size of auxiliary materials is often 5 mm or less, with an average particle size of 0.5-2.0 mm. The particle size of coke is adjusted to 3 mm or less, with an average particle size of 1.0-1.5 mm.

[0003] The sintering raw materials are mixed with water and granulated. The granulated particles are called pseudoparticles. The structure of pseudoparticles is that particles with a diameter of 0.5 mm or less adhere to particles with a diameter of 2 mm or more, resulting in an average diameter of 2.5 to 3.5 mm. The particle size of the granules depends in a complex manner on the moisture conditions in the granulation process, the granulation characteristics of the iron ore, and equipment factors.

[0004] Patent Document 1 discloses a method in which the moisture content of the sintering raw material is changed within a range of 0 to 20% by mass to produce a compression molded body, the "adhesion strength" of the molded body, which is the vertical breaking force per unit area, is measured, the moisture content relative to the maximum value is determined, and this is set as the optimal moisture content required for granulation. In order to achieve the optimal moisture content in the sintering raw material, moisture that is insufficient in the sintering raw material to be granulated is added or excess moisture is removed, and the moisture content is further homogenized, and the resulting sintering raw material with the adjusted moisture content is then granulated. However, the method disclosed in Patent Document 1 is a method for predicting the optimum granulation moisture content of raw materials for the sintering method, and does not provide guidelines for designing an optimum granulation process.

[0005] For the convenience of the following explanation, the method for measuring adhesive force will be explained using Patent Document 1. Fig. 10 is a schematic diagram of the molding machine for the mixture disclosed in Patent Document 1. To measure the adhesive strength, a predetermined amount of water is added to the sintering raw material, and after mixing until the whole is uniform, it is filled into a cylindrical container a. Using a pressure molding machine, it is compression molded to a predetermined height and porosity. Figure 9 is a schematic diagram of the adhesion force measuring device disclosed in Patent Document 1, and the raw material for sintering formed by the pressure molding machine shown in Figure 10 is set in the device shown in Figure 9. The lower container a2 is fixed to the stopper b, and the tensile jig c is attached to the upper container a1. Next, the measurement is started by driving the motor g in Figure 9 to wind the wire h at a predetermined speed, and the tensile load on the parting surface a3 is continuously recorded in the load measuring device f, and the motor g is automatically stopped when the upper container a1 and the lower container a2 are separated. The load (g) when the motor g stops is calculated as the cross-sectional area of ​​the sample a3 (cm 2 ) divided by the adhesive strength (g / cm 2 )

[0006] In Non-Patent Document 1, the relationship between wettability of ore and its pseudo-granulation property is investigated, focusing on wettability, which is important in relation to water, among the surface properties of ore. Specifically, the wettability is measured by measuring the heat of wetting with a minimum calorimeter, and it is found that there is a correlation between the heat of wetting and the pseudo-granulation index (GI). However, this does not provide a guideline for designing an optimal granulation process.

[0007] Powdered iron ore is agglomerated by sintering or briquetting. As a pre-treatment for these agglomeration methods, it is granulated by rolling granulation or briquetting (compression molding). Furthermore, when granulating fine ore into pellet feed, both the tumbling granulation method and the briquetting method are used as pre-treatment. Efficient granulation can be achieved by using the optimum granulation process depending on the characteristics of the fine iron ore ore. However, since there is no established method for selecting the optimal granulation process in advance based on the ore characteristics, trial and error is required, and efficient granulation has not been possible. Furthermore, there is no established method for processing raw materials that is compatible with existing granulation processes, so trial and error is required, making it impossible to achieve efficient granulation. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Publication No. 09-241765 [Non-patent literature]

[0009] [Non-Patent Document 1] “Pseudo-granulation of sintering raw materials”, Flotation, Vol.28(1981), No.2, p.99~109 Summary of the Invention [Problem to be solved by the invention]

[0010] The present invention aims to provide a method for designing an iron ore granulation process that can determine the optimal granulation process in advance based on the characteristics of the raw material, powdered iron ore or fine ore, without the need for trial and error, and to provide a raw material processing method that is compatible with existing granulation processes. [Means for solving the problem]

[0011] As a result of extensive research and development, the inventors have discovered that when granulating iron ore, by determining the range (hereinafter referred to as the "condition range") of adhesiveness and fluidity of the iron ore (hereinafter referred to as the "granulation raw material") that can be formed by the granulation process, and then measuring the adhesiveness and fluidity of the iron ore to be used and selecting a granulation process that includes the condition range of the granulation process, iron ore can be granulated using the optimal granulation process without the need for trial and error. Furthermore, the inventors discovered that by performing preliminary processing such as crushing, blending, and moisture adjustment of the iron ore so that the adhesiveness and fluidity of the iron ore are included in the condition range of the existing granulation process, it is possible to granulate using the optimal iron ore in the existing granulation process without the need for trial and error. The present invention has been made based on the above findings, and the gist of the present invention is as follows.

[0012] (1) A first aspect of the present invention is a design method for selecting an available granulation process from a plurality of iron ore granulation processes, Determining the range of adhesiveness and fluidity conditions of the granulation raw material that can be granulated for each of the plurality of iron ore granulation processes; Measuring the adhesiveness and fluidity of the iron ore to be granulated; The method includes a step of selecting a granulation process capable of granulating the iron ore to be granulated based on the respective condition ranges of the plurality of iron ore granulation processes and the measured values ​​of the adhesion and fluidity of the iron ore.

[0013] (2) In the step of selecting a granulation process capable of granulating the iron ore to be granulated in (1) above, The method may include a step of adopting a granulation process having a condition range when the measured values ​​of the adhesion and fluidity of the iron ore fall within any of the condition ranges.

[0014] (3) In the step of measuring the adhesion and fluidity of the iron ore in (1) or (2), The adhesiveness and fluidity of the iron ore may be measured for each moisture content, and the maximum, minimum, or median value of the obtained values ​​may be used as the measured value.

[0015] (4) The granulation process in (1) or (2) above may be a rolling granulation method or a briquetting method.

[0016] (5) A method for processing iron ore that makes it possible to use a predetermined granulation process, Determining the range of adhesiveness and flowability conditions of a granulation raw material that can be granulated for a predetermined granulation process; Measuring the adhesiveness and fluidity of the iron ore to be granulated; and treating the iron ore to be granulated so that it falls within a predetermined range of conditions for the granulation process.

[0017] (6) In the step of treating the iron ore to be granulated so as to fall within the predetermined range of conditions of the granulation process in (5) above, The method may include a step of adjusting at least one of the particle size and blend of the iron ore to be granulated.

[0018] (7) In the step of measuring the adhesiveness and fluidity of the iron ore to be granulated in the above (5) or (6), The adhesiveness and fluidity of the iron ore may be measured for each moisture content, and the maximum, minimum, or median value of the obtained values ​​may be used as the measured value.

[0019] (8) The predetermined granulation process in (5) or (6) above may be a tumbling granulation method or a briquetting method.

[0020] (9) In the above (1) or (2), specific energy may be used as the index of fluidity.

[0021] (10) In the above (5) or (2), specific energy may be used as the index of fluidity. [Effects of the Invention]

[0022] By evaluating in advance the adhesiveness and fluidity of the iron ore to be granulated, and the range of adhesiveness and fluidity of the various granulation processes to be selected, it is possible to achieve the remarkable effect of selecting the granulation process that is most suitable for the iron ore to be granulated, without having to go through trial and error, such as repeatedly conducting actual and laboratory-scale tests of various granulation processes. When the granulation process has been determined, the adhesiveness and fluidity of the iron ore to be granulated can be adjusted in advance so that they fall within the range of conditions for the granulation process, which has the remarkable effect of enabling optimal granulation to be carried out efficiently. [Brief explanation of the drawings]

[0023] [Figure 1] 1A is a diagram illustrating the ranges of adhesive force and specific energy for the briquetting method and the rolling granulation method. Fig. 1(a) is a diagram illustrating the ranges of adhesive force and specific energy for the rolling granulation method and the briquetting method, with adhesive force on the horizontal axis and specific energy on the vertical axis. Fig. 1(b) is a diagram illustrating the ranges where the briquetting method is suitable (region 4), where the rolling granulation method is suitable (region 2), where both the briquetting method and the rolling granulation method are suitable (region 3), and where neither the briquetting method nor the rolling granulation method is suitable (region 1), with adhesive force on the horizontal axis and specific energy on the vertical axis. [Figure 2] FIG. 1 is a diagram illustrating the relationship between the moisture content (mass%) of the raw material to be granulated and the adhesive force (gf / cm2). [Figure 3] FIG. 2 is a diagram illustrating the relationship between the moisture content (mass%) of iron ore to be granulated and the specific energy (mJ / g). [Figure 4] In order to explain the formability of a single brand of iron ore, the effect of blending multiple ores, and the effect of crushing, the maximum values ​​of adhesive force and specific energy are plotted for each ore. Figure 4(a) shows the effect of the ore brand, Figure 4(b) shows the effect of blending, and Figure 4(c) shows the effect of crushing. [Figure 5]5(a) and 5(b) are diagrams illustrating the optimum range for the granulation process. The optimum range for the tumbling granulation method is shown in Fig. 5(a), and the optimum range for the briquetting method is shown in Fig. 5(b). The diagrams illustrate process changes due to moisture content manipulation. [Figure 6] FIG. 1 is a diagram illustrating a method for determining the minimum value of adhesive force in the briquetting method and the rolling granulation method. [Figure 7] FIG. 1 is a diagram illustrating a method for determining the maximum and minimum values ​​of the specific energy in a tumbling granulation method. [Figure 8] FIG. 1 is a diagram illustrating a method for determining the maximum value of the specific energy in the briquetting method. [Figure 9] FIG. 1 is a schematic diagram of an adhesion measuring device. [Figure 10] FIG. 1 is a schematic diagram of a molding machine for a mixture. DETAILED DESCRIPTION OF THE INVENTION

[0024] (First embodiment) The first embodiment of the present invention is a method for designing a granulation process for raw materials described in (A) to (D). (A) A design method for selecting an available granulation process from among a plurality of iron ore granulation processes, comprising: Determining the range of adhesiveness and fluidity conditions of the granulation raw material that can be granulated for each of the plurality of granulation processes; Measuring the adhesiveness and fluidity of the iron ore to be granulated; The method includes a step of selecting a granulation process capable of granulating the iron ore to be granulated based on the condition ranges of each of the plurality of granulation processes and the measured values ​​of the adhesion and fluidity of the iron ore. (B) In the step of selecting a granulation process capable of granulating the iron ore to be granulated in (A), The method may include a step of adopting a granulation process having a condition range when the measured values ​​of the adhesion and fluidity of the iron ore fall within any of the condition ranges. (C) In the step of measuring the adhesion and fluidity of the iron ore in (A) or (B), The adhesiveness and fluidity of the iron ore may be measured for each moisture content, and the maximum, minimum, or median value of the obtained values ​​may be used as the measured value. (D) The granulation process in the above (A) to (C) may be a rolling granulation method or a briquetting method.

[0025] Before describing the detailed steps of the first embodiment of the present invention, the effects of the adhesion force of iron ore, the specific energy of iron ore, and the moisture content of iron ore will be described.

[0026] (adhesion of iron ore) The adhesion of the iron ore can be expressed by the following various adhesion evaluation test values. These adhesion indices evaluate the static state after the granules are formed. In other words, they evaluate the strength characteristics of the granules. Therefore, one of the simplest methods is to use crushing strength, which can be measured by the crushing strength test method for pellets, briquettes, and other compacts, which is widely used in the industry. A more sophisticated method is to evaluate the adhesion strength by a shear test of the powder layer, for example, the method specified in the Japan Powder Process Industry and Technology Association Standard SAP15-13. The index obtained from this is called adhesive strength. The static strength σ of a wet granulated material is theoretically expressed by the following Rumpf equation: σ=((1-ε)F) / (εd 2 ) …(Formula 2) where ε is the porosity of the powder layer, d is the particle diameter, and F is the adhesive force between two particles. Since F depends on the wettability of iron ore with water, it is thought to be related to the heat of wetting. Therefore, the measured value of the heat of wetting can be used as an indicator of the adhesion of iron ore.

[0027] (Iron ore liquidity) The fluidity of a material is an index of the characteristics of a powder layer in a dynamic state. So-called "poor fluidity" means that the dynamic adhesion tends to be strong. In other words, fluidity is also a characteristic related to the ease of growth of granulated material in, for example, a tumbling granulation method. The fluidity of a substance is usually evaluated as viscosity, and viscosity can be used as an index of fluidity. However, in the case of powdered or granular materials such as iron ore, viscosity measurement is often difficult. Therefore, the "angle of repose," which is the maximum angle of the slope at which powder or granular material remains stable without spontaneously collapsing when piled up, can be used as an index of the fluidity of powder or granular material. Powders with good fluidity tend to have a small angle of repose. Another index of the fluidity of powder or granular material is the bulk density of the packed bed after tapping or vibrating the packed bed. Powders with good fluidity tend to have a large bulk density of the packed bed. The fluidity of iron ore is preferably measured in a wet state, similar to the raw material used in the actual granulation process. However, measurements of the angle of repose and packed bed bulk density are basically applied to raw materials that have relatively good fluidity in a dry state, and it is often difficult to measure accurately for wet raw materials that have very poor fluidity. Therefore, it is preferable to use an index of fluidity that can be stably measured even in a wet state, and it is preferable to use the specific energy described below. Since viscosity becomes a force under a certain velocity gradient, the "force required to maintain flow" can be measured as an index of fluidity. Furthermore, the "force required to maintain flow" can be converted into energy by integrating it over a certain distance. Here, we focus on the fact that substances with poor fluidity require a lot of energy to flow and have a high cohesive tendency, so they tend to aggregate and form clumps, and measure the specific energy required for flow using the following procedure to use it as an index of the fluidity of the substance. Specific energy is a more measurable and preferable index than viscosity. Step 1: Measure the flow energy using a powder flowability analyzer. Step 2: The measured flow energy is converted into specific energy [mJ / g] as flow energy [mJ] per 1 [g] of sample. As a powder fluidity analyzer, for example, a "Powder Rheometer FT4 manufactured by Sysmex Corporation" can be used. The measurement principle using the Sysmex Corporation Powder Rheometer FT4 is detailed in the Sysmex Corporation "Powder Fluidity Analyzer Powder Rheometer FT4 Instruction Manual (Supplement) Created: 2006 / 09 / 01; Revised: 2007 / 01 / 01." The gist of the measurement is that "a cylindrical container is filled with a powder sample, and the blade rotates through the powder from H1 to H2. The resulting "vertical load" and "rotational torque" are integrated over the blade's travel distance, and the total resulting work [mJ] is measured and used as an index of fluidity." Specifically, if the vertical load [N] acting on the blade is F and the rotational torque [Nm] is T, the flow energy E can be calculated using the following formula:

[0028]

number

[0029] (Effect of moisture content of iron ore) Adhesion and fluidity are affected not only by the properties of the iron ore itself, but also by the moisture content of the iron ore. Fluidity decreases with increasing moisture content, and dynamic adhesion increases. When the filling state of the powder and water exceeds the plastic limit moisture content, at which point the powder changes from the fanicular region to the capillary region, the powder becomes paste-like and becomes more fluid. Since the rolling granulation method and briquetting method granulate under moisture conditions below the plastic limit, fluidity is evaluated in that moisture range. Note that adhesion is also evaluated in the same moisture range below the plastic limit as fluidity. For adhesiveness and fluidity, values ​​at a specific moisture content can be used as representative values, but the maximum values ​​can also be used as representative values. This is because the moisture content range at which adhesiveness and fluidity are expressed varies depending on the iron ore, and the optimum moisture content during operation also varies depending on the iron ore used in various granulation processes.

[0030] The first embodiment of the present invention includes the following steps 1 to 3.

[0031] <Step 1> This is a step for determining the range of conditions for the granulation process. The granulation process chosen will determine the range of adhesiveness and flowability of the iron ore that the granulation process can form. Figure 1 shows a conceptual diagram illustrating the range of adhesiveness and flowability in the granulation process. The method for determining the range of adhesiveness and fluidity will be described below.

[0032] [Adhesion range] The range of adhesiveness of raw materials appropriate for a certain granulation process is determined taking into consideration the characteristics inherent to the granulation process and the specified values ​​required in the next process using the granulated material. The minimum value that determines the range of adhesiveness of raw materials appropriate for a certain granulation process is the larger of the minimum value determined taking into account the characteristics specific to the granulation process and the minimum value determined taking into account the specified value required for the next process using the granulated material. The maximum value that determines the range of adhesiveness of the raw material shall be the smaller of the maximum value determined taking into consideration the characteristics specific to the granulation process and the maximum value determined taking into consideration the specified value required for the next process. A conceptual diagram of the briquetting method and the rolling granulation method is shown in Figure 1. Here, it is assumed that the adhesiveness range is determined taking into account the specified values ​​required for the next process, and the briquetting method and the rolling granulation method share the same maximum and minimum adhesiveness values. (A) The properties specific to the granulation process are determined by laboratory testing of the granulation method according to the following procedures A1 to A4. Step A1: For each granulation process, granules are made using iron ores with different adhesive strengths. Step A2: Measure the product ratio (hereinafter referred to as "yield") to the input raw materials and the strength of the granules at that time. Step A3: There is a critical lower limit strength value below which the yield drops sharply if the granulated material falls below that value. Therefore, the minimum adhesiveness value resulting from this lower limit strength value is taken as the minimum adhesiveness value. Step A4: The adhesive force corresponding to the maximum granule strength that can be achieved in the granulation process is taken as the maximum adhesiveness. (B) The specified value required for the next process using the granulated material may be determined by procedure B1 from an analysis of the operational performance of the next process using the granulated material. The specified value at this time reflects the equipment conditions (conditions during the transportation process such as sieves and belt transfers) and operational conditions of the next process, which differ from factory to factory. Step B1: As shown in Figure 6, there is a correlation between the granule strength index and adhesive force controlled in the process, so the adhesive force corresponding to the specified value of the lower limit of strength control is set as the minimum value of adhesive force.

[0033] [Liquidity range] The range of flowability of raw materials appropriate for a particular granulation process is similarly determined by taking into consideration the characteristics inherent in the granulation process and the specifications required for the next process in which the granulated material is used. (α) In the case of rolling granulation method The minimum value that determines the range of raw material flowability appropriate for a certain granulation process is the larger of the minimum value determined taking into account the characteristics specific to the granulation process and the minimum value determined taking into account the specified value required for the next process using the granulated material. The maximum value that determines the range of fluidity of the raw material shall be the smaller of the maximum value determined taking into consideration the characteristics specific to the granulation process and the maximum value determined taking into consideration the specified value required for the next process. (A) The properties specific to the granulation process are determined by laboratory testing of the granulation method according to the following procedures A5 to A7. Step A5: For each granulation process, granules are made using iron ores with different fluidity. Step A6: Determine the particle size distribution group of the granulation product specific to the granulation process. Step A7: Determine the maximum and minimum values ​​of fluidity according to the particle size distribution group of the granulated product. The reason why the particle size of the granulated product is used as an indicator rather than its strength is that the strength of the granulated product is ultimately reflected in the particle size of the granulated product. In other words, granulated products with weak strength will collapse during the granulation process, resulting in a small particle size. In addition, granulated products that have grown significantly will also collapse, so the upper particle size of the granulated product is often limited. As the flowability deteriorates, the particle size of the granulated product increases. (B) The specified value required for the next process using the granulated material may be determined by procedure B2 from an analysis of the operational performance of the next process using the granulated material. The specified value reflects the equipment conditions (conditions during the transportation process such as sieves and belt transfers) and operational conditions of the next process, which differ from factory to factory. Step B2: As shown in Figure 7, there is a correlation between the particle size of the granulated product managed in the process and the specific energy, so the specific energy corresponding to the specified lower and upper limits of the target particle size becomes the minimum and maximum values ​​of the specific energy, respectively. In the case of the tumbling granulation method, the range of fluidity is often determined by the procedure when taking into consideration the specified values ​​required in the next process using the granulated material (B). This is to ensure that the particle size of the granulated material meets the specified value required for the next process, which is generally an average particle size of 2.5 to 3.5 mm for sintering raw materials and 10 to 15 mm for pellets.

[0034] (β) Briquette method The specific characteristics of the granulation process are determined and the specified values ​​required for the next process using the granulated material are taken into consideration. (A) The characteristics specific to the granulation process are determined by laboratory testing of the granulation method according to the following procedures A8 to A9. Step A8: For each granulation process, granules are made using iron ores with different fluidity. Step A9: Measure the relationship between molding yield and fluidity. There is a range of fluidity for raw materials that allows stable molding operations. If the fluidity deteriorates beyond this range, the smooth flow of the raw material into the rolls is hindered, and it becomes difficult to remove the material from the cup of the briquetting machine, resulting in a decrease in yield. On the other hand, if the fluidity improves beyond this range, the shape of the briquette cannot be maintained, resulting in a decrease in yield. As shown in Figure 8, if the horizontal axis is specific energy and the vertical axis is molding yield, a relationship with an upward convex shape is obtained. (B) Consider the specified values ​​required for the next process using the granulated material. In the case of the briquetting method, the lower limit of the yield is determined by the specified value required for the next process, which is determined for each factory depending on the production volume and manufacturing costs. As shown in Figure 8, the range of fluidity corresponds to the lower limit of the allowable yield. Since a high yield is desirable, the specific energy that maximizes the yield is most desirable.

[0035] <Step 2> This is the step to measure the range of adhesion and fluidity of iron ore. The adhesive force and specific energy of the iron ore to be granulated, for example, when it contains moisture, are measured at several points, and the maximum, minimum, or median values ​​are taken as the maximum, minimum, or median values ​​of the adhesive force and the maximum, minimum, or median values ​​of the specific energy, respectively. The method used for the measurement is the same as that described in step 1, so it will be omitted here. As will be explained later, Figures 2 and 3 show examples of measurements of adhesive force and specific energy at several points when the iron ore to be granulated contains moisture.

[0036] <Step 3> This is a step of selecting a granulation process that can produce granules. A granulation process is selected that covers the range of conditions for the adhesiveness and fluidity of the iron ore to be granulated measured in step 2. For example, based on Figure 1, the granulation process most suitable for the iron ore in question can be determined from two indicators: the adhesive strength and specific energy of the iron ore. If the adhesive strength and specific energy values ​​of the iron ore fall within region 1 in Figure 1(b), neither the tumbling granulation method nor the briquetting method is suitable. If it falls within region 2 or region 4, then the tumbling granulation method or the briquetting method is the suitable granulation process, respectively. If it falls within region 3, then both the tumbling granulation method and the briquetting method can be adopted.

[0037] (Second embodiment) A second embodiment of the present invention is an iron ore processing method as set forth in (E) to (H). (E) A method for processing iron ore that utilizes a predetermined granulation process, comprising: Determining the range of adhesiveness and flowability conditions of the granulation raw material that can be granulated in the predetermined granulation process; Measuring the adhesiveness and fluidity of the iron ore to be granulated; and treating the iron ore to be granulated so that it falls within the predetermined range of conditions for the granulation process. (F) In the step of treating the iron ore to be granulated so that it falls within the predetermined range of conditions of the granulation process in (E), The method may include a step of adjusting at least one of the particle size and blend of the iron ore to be granulated. (G) In the step (E) or (F) above, the adhesiveness and fluidity of the iron ore to be granulated are measured. The adhesiveness and fluidity of the iron ore may be measured for each moisture content, and the maximum, minimum, or median value of the obtained values ​​may be used as the measured value. (H) The granulation process in the above (E) to (G) may be a rolling granulation method or a briquetting method.

[0038] The second embodiment of the present invention includes the following steps 4 to 6.

[0039] <Step 4> This is a step for determining the range of conditions for the granulation process. A predetermined granulation process determines the range of adhesiveness and fluidity of the iron ore that can be molded. Figure 1 shows a conceptual diagram showing the adhesiveness and fluidity range of the granulation process. The method used for determination is the same as that described in Step 1.

[0040] <Step 5> This is the step to measure the range of adhesion and fluidity of iron ore. The adhesion force and specific energy of the iron ore to be granulated are measured while changing the moisture content. The method used for the measurement is the same as that described in step 1, so it is omitted here. As will be explained later, Figures 2 and 3 show examples of measurements of adhesive force and specific energy for various iron ores with varying moisture content.

[0041] <Step 6> This is a step for preparing the iron ore to be granulated. When the adhesiveness and fluidity of the iron ore to be granulated do not fall within the range of conditions for the granulation process by adjusting the moisture content alone, the particle size of the iron ore can be adjusted by crushing or classifying the iron ore, or the blending ratio of multiple iron ores can be adjusted, or both the particle size and the blending can be adjusted to bring the adhesiveness and fluidity of the iron ore to be granulated within the range of conditions. This allows the use of the iron ore to be granulated in the target granulation process. [Example]

[0042] Hereafter, "iron ore A" will be written as "OreA". In the examples, three types of ores from Brazil (OreA, OreB, OreD) and two types of ores from Canada (OreC, OreE) were used as samples. OreA-1 to OreA-3 were prepared by grinding OreA to three different particle sizes. OreF-1 to OreF-3 were prepared by mixing OreD and OreE at blending ratios of 25:75, 50:50, and 75:25. Table 1 shows the Blaine specific surface area of ​​various ores. [Table 1] In Example 1, an example is shown in which the adhesive force of iron ore and the specific energy of iron ore are measured. In Example 2, an example is shown in which the particle size or blend of iron ore is changed to adjust the adhesiveness and fluidity. In Example 3, an example is shown in which a granulation range for a predetermined granulation process is determined.

[0043] [Example 1] (adhesion of iron ore) The adhesive force was measured according to the method disclosed in Japanese Patent Publication No. 9-241765. The mixture molding machine shown in FIG. 10 and the adhesive force measuring device shown in FIG. Figure 2 plots the change in adhesive strength of each ore due to moisture content. In Figure 2, the horizontal axis represents moisture content (mass%) and the vertical axis represents adhesive strength (gf / cm 2 ) The adhesive force curved upwards with increasing water content. Adhesion can be considered as the product of the strength of the liquid bridge force between two particles and the number of liquid bridges per unit cross-sectional area. When water is added, the number of liquid bridges between ore particles increases, and therefore the adhesive force increases. However, since the liquid bridging force between two particles generally decreases with an increase in moisture content, there exists a moisture content at which the adhesive force exhibits a maximum value.

[0044] (specific energy of iron ore) The specific energy was measured using a Freeman Technology FT4 Powder Rheometer. The measurement sample was filled to a height of 50 mm in a cylindrical container with an inner diameter of 25 mm, the blade tip speed was set to 100 mm / s, and the blade approach angle was set to 5°. Figure 3 plots the change in specific energy of each ore depending on the moisture content. In Figure 3, the horizontal axis is moisture content (mass%) and the vertical axis is specific energy (mJ / g). As shown in Figure 3, the specific energy increases as the moisture content increases, and then suddenly drops. The reason for this sudden drop in specific energy is that the moisture content becomes excessive, causing the powder and water packing state to change from the fanicular region to the capillary region, and the powder becomes paste-like.

[0045] (Effect of moisture content) Figure 5 shows a graph summarizing the changes in adhesive force and specific energy depending on the moisture content of OreB from Examples 1 and 2. Within the moisture content range of 6 to 10%, which is the range typically used for granulation, adhesive force decreases while specific energy increases as the moisture content increases. In many cases, tumbling granulation of ore is carried out in a moisture content range where the specific energy is at its maximum, and adhesive force often reaches its maximum value at moisture content conditions lower than that moisture content range.

[0046] [Example 2] The maximum values ​​of adhesive force and specific energy for each ore obtained when the moisture content was changed in Example 1 were plotted and shown in Figure 4. Figure 4(a) shows the effect of the ore brand, Figure 4(b) shows the effect of blending, and Figure 4(c) shows the effect of crushing.

[0047] (Impact of iron ore brands) As shown in FIG. 4(a), OreA (OreA-1, OreA-2, OreA-3), OreB, OreC, and OreD all have high adhesive strength and specific energy. On the other hand, OreE has low adhesive strength. Thus, the adhesive force and specific energy vary greatly depending on the type of ore.

[0048] (Effect of combining multiple ores) The changes in adhesive strength and specific energy due to the combination of OreE and OreD were examined. As shown in Figure 4(b), as the blending ratio of OreD increases from OreE to OreF-1, OreF-2, and OreF-3, the adhesive strength increases significantly, but the change in specific energy is small. On the other hand, in the range from OreF-3 to OreD, as the blending ratio of OreD increases, the change in adhesive strength is small, but the specific energy increases significantly.

[0049] (Effect of crushing) As shown in Figure 4(c), when OreA-1 was pulverized to produce OreA-2 or OreA-3, the adhesive strength increased. This means that this method is effective in improving the strength of the granulated product.

[0050] [Example 3] An example of determining the granulation range of a predetermined granulation process is shown below. In the example of the tumbling granulation method, a dish granulator was used, and in the example of the briquetting method, a briquetting tester was used. (Dish-type granulation test) The dish granulation test was carried out using a dish granulator with an inner diameter of 600 mm and a depth of 150 mm. The granulation conditions were a dish rotation speed of 13.5 rpm, an angle of 55°, and a rolling time of 10 min. The amount of raw material input was 2 kg, and the raw material moisture content was adjusted for each iron ore to the moisture value that results in the specific energy shown in Figure 5(a). The appropriate range for the tumbling granulation method was determined to be a rate of ungranulated powder of 1 mm or less of 10 mass% or less and a crushing strength of the granulated product of 10 N or more. The appropriate range for tumbling granulation is shown in Figure 5(a). OreE, OreF-1, and OreF-2 did not grow due to their low specific energy, and were therefore unsuitable for use. The other iron ores had good grain growth and granule strength, making them suitable for rolling granulation. (Briquette molding test) The briquette forming test was carried out using a briquette forming machine having a forming roll with an outer diameter of 650 mm and a width of 200 mm, and 96 forming cups with dimensions of 20 mm length x 20 mm width x 8.5 mm height arranged in 9 rows per circumference. The forming conditions were a forming roll rotation speed of 3 rpm, a raw material input of 20 kg, and the raw material moisture content was adjusted for each iron ore to the moisture value that would result in the specific energy shown in Figure 5(b). The appropriate range for briquetting was determined when the forming yield was 80% or more and the crushing strength of the compact was 20 N or more. The appropriate range for briquetting is shown in Figure 5(b). Ore A (A-1, A-2, A-3), Ore B, Ore C, and Ore D had high specific energies, which resulted in poor flow of iron ore into the forming rolls and reduced forming yield, making them unsuitable for use. OreE and OreF-1 had low adhesive strength and were therefore unsuitable for use, whereas OreF-2 and OreF-3 had good flowability into the forming rolls and good strength of the compacts, making them suitable for briquetting. [Industrial Applicability]

[0051] The present invention can be used in a method for designing a granulation process for powdered iron ore and fine iron ore, and in an iron ore processing method using the same. [Explanation of symbols]

[0052] a: cylindrical container, a1: upper container, a2: lower container, a3: dividing surface, a4: bottom surface area, b: stopper, c: tension jig, d: pulley, e: pulley, f: load measuring device, g: motor, h: wire, i: push plate, j: handle.

Claims

1. A design method for selecting an available granulation process from a plurality of iron ore granulation processes, comprising: Determining the range of adhesiveness and fluidity conditions of the granulation raw material that can be granulated for each of the plurality of iron ore granulation processes; Measuring the adhesiveness and fluidity of the iron ore to be granulated; A step of selecting a granulation process capable of granulating the iron ore to be granulated based on the condition ranges of each of the plurality of iron ore granulation processes and the measurement values ​​of the adhesion and fluidity of the iron ore; A method for designing an iron ore granulation process, comprising:

2. In the step of selecting a granulation process capable of granulating the iron ore to be granulated, A method for designing an iron ore granulation process as described in claim 1, characterized in that it includes a step of adopting a granulation process having a condition range when the measured values ​​of the iron ore's adhesion and fluidity fall within any of the condition ranges.

3. In the step of measuring the adhesion and fluidity of the iron ore, A method for designing an iron ore granulation process according to claim 1 or claim 2, characterized in that the adhesion and fluidity of the iron ore are measured for each moisture content, and one of the maximum, minimum, or median values ​​obtained is used as the measured value.

4. 3. The method for designing a granulation process for iron ore according to claim 1 or claim 2, wherein the granulation process is a rolling granulation method or a briquetting method.

5. 1. A method for processing iron ore that makes use of a predetermined granulation process, comprising: Determining the range of adhesiveness and flowability conditions of a granulation raw material that can be granulated for a predetermined granulation process; Measuring the adhesiveness and fluidity of the iron ore to be granulated; Treating the iron ore to be granulated so that it falls within a predetermined range of conditions for the granulation process; A raw material processing method comprising the steps of:

6. In a step of treating the iron ore to be granulated so that it falls within a predetermined range of conditions for the granulation process, 6. The raw material processing method according to claim 5, further comprising a step of adjusting at least one of the particle size and composition of the iron ore to be granulated.

7. In the step of measuring the adhesiveness and fluidity of the iron ore to be granulated, 7. A raw material processing method according to claim 5, wherein the adhesiveness and fluidity of the iron ore are measured for each moisture content, and the maximum, minimum or median of the obtained values ​​is used as the measured value.

8. 7. The raw material processing method according to claim 5, wherein the granulation process is a rolling granulation method or a briquetting method.

9. 3. The method for designing a granulation process according to claim 1, wherein specific energy is used as the index of fluidity.

10. 7. The raw material processing method according to claim 5, wherein specific energy is used as the index of fluidity.

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