Powder property modification method and method for producing sintered ore

Abstract

Proposed is a powder property modification technique that allows heating with good productivity when a water-containing bulk material is being granulated and heated. The present invention is a powder property modification method in which, during granulation and heating of a water-containing bulk material, when a chemical agent having at least one chosen from the group consisting of polymer flocculants, inorganic flocculants, and a water-absorbing materials as a principal constituent is added before granulation or during a granulation step, the quantity of the chemical agent added is adjusted in accordance with the water content of the water-containing bulk material or an operation index correlated with the water content of the water-containing bulk material. The present invention is a method for producing a sintered ore that includes: a powder property modification step in which, in accordance with this powder property modification method, the quantity of the chemical agent added is adjusted in accordance with the water content of a raw material for sintering or the operation index correlated with the water content of the water-containing bulk material; a granulation step in which the property-modified raw material for sintering is granulated using a granulator; and a sintering step in which the granulated raw material for sintering is sintered using a sintering machine.

Description

Method for modifying powder properties and method for producing sintered ore

[0001] The present invention relates to a method for modifying the properties of moisture-containing powder, which was developed to eliminate problems caused by moisture generated during granulation and heating of moisture-containing bulk material, and also to a method for producing sintered ore using the modification method.

[0002] Powders and granules, such as various ores, by-product slag from ore refining and steelmaking, and by-products from petroleum distillation and rectification, are called bulk materials. Bulk materials often contain fine powder. Therefore, they are granulated, fired, and adjusted to a specified particle size to be used as raw materials. In the steel industry, powdered iron ore is mixed with limestone and coke powder, and after adding water, the mixture is granulated into pseudo-particles of a specified size. The pseudo-particles adjusted to the appropriate size and properties are fed into a sintering machine, where they ensure breathability and other properties, improving the productivity of sintered ore.

[0003] On the other hand, bulk materials are often stored in open-air yards or transported exposed to the air. When rainfall accumulates in these conditions, the bulk material can become highly moist. This state is called moist bulk material. It is known that proper moisture content must be controlled when granulating such moist bulk material; excessive moisture in the granulated material reduces breathability, lowering the productivity of the granulated material and causing a decline in quality. On the other hand, excessive capital investment is required to remove moisture. For example, methods such as mixing dry raw materials stored in a silo beforehand can be used.

[0004] To address this problem, methods such as those disclosed in Patent Documents 1 to 3 have been used.

[0005] Patent Document 1 discloses a method for treating raw materials for sintering, which suppresses adhesion between low-alumina ores, uniformly mixes high-alumina ores with low-alumina ores, and suppresses uneven distribution of alumina. This technology adds an adhesion inhibitor to the low-alumina ore during granulation, and obtains a blended powder in which at least the low-alumina ore and the high-alumina ore are uniformly dispersed.

[0006] Patent Document 2 discloses a method for treating wet bulk materials to eliminate the problem of impediments to loading on a belt conveyor caused by the unavoidable formation of slurry-like spring water when loading wet bulk materials. In this technology, a flocculant is attached to the wet bulk materials to prevent the formation of spring water when loading the bulk materials, thereby improving handling.

[0007] Patent Document 3 discloses a technology in which a flocculant or water absorbent is added to moist bulk material, causing the powder to retain moisture and preventing equipment shutdowns due to adhesion, blowouts and backflows during transport, collapse of stockpiles, etc. When applied to a granulation method for raw material for sintering, it prevents small particle size powder from the moist bulk material from solidifying unevenly, which prevents a decrease in the strength of the granulated material and leads to improved yield during sintering, uniformity of the mineral structure, and improved productivity.

[0008] JP 2017-125247 A International Publication No. 2015 / 151524 International Publication No. 2024 / 004298

[0009] However, the above-mentioned conventional technologies have had the following problems. For example, when the raw material, wet bulk material, contains excessive moisture, a measure of mixing it with dry raw materials stored in a silo or the like has the problem that the size of the silo is limited, the period that can be used is short, and the effectiveness is limited. A measure of reducing the moisture content by storing all the raw materials to be used in a covered space for a long period of time has the problem of securing the land necessary to construct the necessary building and increasing the equipment costs.

[0010] Furthermore, Patent Document 1 does not disclose any viewpoint of contributing to the productivity of sintered ore by controlling the concentration of the chemicals, and there is a problem that it is not applicable to a single brand or brands with the same alumina content.

[0011] Furthermore, the technology described in Patent Document 2 focuses on the handleability of the powder, and does not consider the productivity of sintering or the correlation between granulation properties and breathability, etc. Furthermore, the technology described in Patent Document 3 only describes that it contributes to improving the productivity of sintering, and does not consider the appropriate drug concentration.

[0012] These conventional technologies were insufficient in improving the aeration inhibition caused by water itself in the operating area, which exceeds the moisture content suitable for granulation due to rainfall at steelworks or from raw materials.This technology improves sinter productivity or quality by improving aeration in the moisture range above the optimum moisture value for granulation, which these existing technologies cannot address.

[0013] The present invention has been made in consideration of the above circumstances, and aims to propose a powder property modification technology that can be used to granulate moist bulk material and heat it with good productivity when heating it, from the purpose of evaporating water to the high-temperature heating process involving a reaction, such as firing. In particular, the present invention aims to achieve improved air permeability in high-moisture ranges that cannot be achieved with conventional technologies, and to propose a method for producing sintered ore that uses moist bulk material as a raw material and improves productivity.

[0014] The powder property modification method of the present invention, which advantageously solves the above-mentioned problems, is characterized in that when hydrated loose material is granulated and heated, a chemical agent whose main component is one or more selected from polymer flocculants, inorganic flocculants, and polymer water absorbents is added to the hydrated loose material before or during the granulation process, and the amount of the chemical agent added is adjusted depending on the moisture content of the hydrated loose material or an operational index that is correlated with the moisture content of the hydrated loose material.

[0015] In addition, a more preferable solution for the powder property modification method of the present invention is when the hydrated bulk material is at least one of ore, by-product slag from ore refining or steel production, and by-products from petroleum distillation and rectification.

[0016] The method for producing sintered ore according to the present invention, which advantageously solves the above-mentioned problems, is a method for producing sintered ore by granulating and heating sintering raw materials containing iron-containing raw materials, carbon-containing raw materials, and CaO-containing raw materials as moist bulk materials, and is characterized by including a powder property modification process in which the amount of the chemicals to be added is adjusted according to the moisture content of the sintering raw materials or an operational index correlated with the moisture content of the moist bulk materials, according to any of the above-mentioned powder property modification methods; a granulation process in which the sintering raw materials with modified properties are granulated in a granulator; and a sintering process in which the granulated sintering raw materials are sintered in a sintering machine.

[0017] In the method for producing sintered ore according to the present invention, it is more preferable to adjust the amount of chemicals added in the powder property modification step according to the permeability index in the sintering step or an operating condition index that is correlated with permeability.

[0018] According to the powder property modification method of the present invention, when granulating and heating the hydrated loose grain, a flocculant or a water-absorbing material is added depending on the moisture content of the loose grain, which can suppress the deterioration of breathability during heating due to excessive moisture. This has the effect of preventing the associated deterioration of productivity. In addition, the improvement of raw material diffusibility also has the effect of homogenizing the product.

[0019] 1 is a graph showing the effect of chemical addition on the relationship between the harmonic mean diameter and moisture content of granulated particles when sinter raw material is granulated. FIG. 2 is a graph showing the effect of chemical addition on the relationship between the permeability index and moisture content when granulated particles are heated. FIG. 3 is a graph showing the effect of chemical addition on the relationship between the heating time and moisture content of granulated particles. FIG. 4 is a graph showing the effect of chemical addition on the relationship between the productivity of sintered ore and the moisture content of granulated particles. FIG. 5 is a graph showing the relationship between the sintered ore production rate of an actual machine and the chemical concentration relative to the moisture content. FIG. 6 is a graph showing the relationship between the rate of productivity at an appropriate moisture value and the chemical concentration relative to the moisture content. (a) A graph showing the relationship between the amount of moisture added when granulating sinter raw material and the harmonic mean diameter of granulated particles and the permeability during heating, and (b) is a schematic diagram of particle morphology.

[0020] The following describes in detail the embodiments of the present invention. The following embodiments are merely examples of methods for realizing the technical idea of ​​the present invention, and are not intended to limit the configuration to the following. In other words, the technical idea of ​​the present invention can be modified in various ways within the technical scope described in the claims.

[0021] In this embodiment, a method for producing sintered ore using a powder property modification method will be described as an example. Equipment suitable for the method for producing sintered ore according to this embodiment includes chemical addition equipment, a granulator, and sintering equipment. The sintering equipment includes a sintering machine, a crusher, and a control device. In this embodiment, examples of the bulk materials that are the target of moisture-containing bulk materials include ores, by-product slag from ore refining and steel production, and by-products from petroleum distillation and rectification. Examples of ores include iron ore, coal, limestone, dolomite, silica, magnesite, and other MgO sources, as well as nickel and manganese ores.

[0022] In the chemical addition equipment, it is preferable to spray a liquid chemical or sprinkle a powdered chemical, and then mix the powdered loose material with a dedicated mixer. Instead of a dedicated mixer, mixing with a crusher or heavy machinery, or the impact of a conveyor belt transfer drop, can also be used. This mixing method aims to diffuse the chemical into the powder. This process is the powder property modification process.

[0023] The granulator granulates sinter raw materials containing an iron-containing raw material, a carbon-containing raw material, and a CaO-containing raw material to form granulated particles. When the granulator granulates the granulated particles, granulation water is added to the sinter raw materials. This process is the granulation process. The granulated particles granulated by the granulator are transported to the sintering machine. The iron-containing raw material is, for example, iron ore or dust generated in a steel mill. The carbon-containing raw material is, for example, coke powder or anthracite. The CaO-containing raw material is, for example, quicklime, limestone, slag, etc. Other necessary components may be blended.

[0024] The sintering machine is, for example, a Dwight Lloyd type sintering machine. The sintering machine includes a raw material supply device, a pallet, a cutoff plate, an ignition furnace, a gas fuel supply device, and a wind box. The raw material supply device charges the granulated particles into the pallet.

[0025] The pallet is an endlessly movable pallet. When granulated particles are charged into the pallet from the raw material supply device, a charging layer of sinter raw material is formed inside the pallet. The cut-off plate flattens the surface of the charging layer and adjusts the thickness of the charging layer to a preset target layer thickness. This process is the charging layer formation step.

[0026] The ignition furnace is provided downstream of the raw material supply device and ignites the carbon-containing raw material contained in the surface layer of the charging bed. The gaseous fuel supply device supplies gaseous fuel to the surface side of the charging bed. As the gaseous fuel, for example, city gas (LNG) is supplied. The gaseous fuel supplied from the gaseous fuel supply device is not limited to city gas, and any combustible gas selected from blast furnace gas, coke oven gas, blast furnace / coke oven mixed gas, converter gas, natural gas, methane gas, ethane gas, propane gas, shale gas, and mixed gases thereof may be used.

[0027] The wind box is installed below the pallet and sucks the air downward from within the sintering bed formed within the pallet. When the wind box sucks the air from within the sintering bed downward, the combustion and melting zone within the sintering bed moves downward. In addition, as the air within the sintering bed is sucked downward, the gaseous fuel supplied from the gaseous fuel supply device is introduced into the sintering bed from the surface layer of the sintering bed. As the pallet moves, the combustion and melting zone within the sintering bed moves downward, and the sintering raw materials in the sintering bed are sintered. A sintered cake is obtained by sintering the sintering raw materials. This process is the sintering step.

[0028] The crusher crushes the sinter cake discharged from the sinter machine into crushed sinter cake. The crushed sinter cake is cooled and sized to produce sintered ore. This process is the crushing step. The sintering process is comprised of the sintering bed formation step, sintering step, and crushing step.

[0029] The control device is a general-purpose computer such as a workstation or personal computer, which has a control unit and a memory unit. The control unit is, for example, a CPU, which controls the operation of the chemical additive equipment, granulator, sinterer, and crusher by executing programs read from the memory unit. The memory unit is, for example, an updatable flash memory, a built-in hard disk or a hard disk connected via a data communication terminal, an information recording medium such as a memory card, and a read / write device for the information recording medium. The memory unit stores programs for the control unit to execute each function, data used by the programs, etc.

[0030] The control unit calculates an air permeability index, such as the airflow resistance of the sintering raw materials stacked on the pallet, from the suction air volume and back pressure of the pallet.The control unit adjusts the granulation conditions of the granulator and the amount of chemicals added in the chemical addition equipment according to the calculated air permeability index.

[0031] When changing the granulation conditions of the granulator, the control unit changes the granulation conditions of the granulator so as to narrow the distribution width of the particle size distribution of the granulated particles. When the distribution width of the particle size distribution of the granulated particles becomes narrow, the packing density of the granulated particles charged to the pallet decreases, and the charging density of the charging bed decreases. The granulation conditions that narrow the distribution width of the particle size distribution of the granulated particles can be determined by conducting granulation experiments in which the rotation speed of the granulator, the amount of sintering raw material charged to the granulator, the amount of granulation water added, etc. are changed and the distribution width of the particle size distribution of the granulated particles is confirmed.

[0032] Furthermore, the control unit may increase the amount of CaO-containing raw material mixed into the sintering raw material. CaO functions as a binder, causing ungranulated powder, which is difficult to granulate, to adhere to the granulated particles, thereby reducing the number of fine particles in the particle size distribution. Therefore, increasing the amount of CaO-containing raw material narrows the distribution width of the particle size distribution of the granulated particles. Note that in the method for producing sintered ore according to this embodiment, increasing the amount of CaO-containing raw material is also included in the change of granulation conditions.

[0033] When adjusting the amount of chemical agent to be added, the control unit adjusts the amount of chemical agent to be added so that the permeability index of the granulated particles when heated approaches a predetermined value. The amount of chemical agent to be added that approaches the permeability index or an operating condition index correlated with permeability to a predetermined value is determined, for example, by measuring the moisture content of the bulk material or an operating index correlated with the moisture content of the bulk material in advance and determining the amount based on the measured value. The operating condition correlated with permeability can also be evaluated using a heat exchange index. Indices that can be used during sintering production include those that involve gas-solid or gas-liquid heat exchange between high-temperature gas and the target powder or water in the pre-drying process of coke feed coal.

[0034] <Granulation and Moisture Content> Figure 7 shows a schematic diagram of the effect of moisture content on the granulated particle size and air permeability during heating when granulating sinter raw materials. In the water absorption region shown in Zone I, moisture 2 is absorbed by the sinter raw materials, particularly fine iron ore 1, resulting in small granulated particle sizes and narrow gaps between granulated particles, resulting in low air permeability during heating. In the granulation region shown in Zone II, moisture 2 that was not fully absorbed by fine iron ore 1 appears on the surface of the fine iron ore, causing the fine iron ore particles to adhere to each other, thereby promoting granulation. As a result, the granulated particle size increases, widening the gaps between granulated particles when stacked, improving air permeability during heating. In the excess moisture region of Zone III, excess moisture exists as liquid water (water film 3) in the gaps between granulated particles, impairing air permeability when stacked. In the example shown in Figure 7, the granulation limit moisture content is approximately 7.5 mass%. In Zone IV, where the amount of water is even more excessive, the fine iron ore 1 floats in the water droplets 4 and becomes a slurry, resulting in smaller granules and poorer aeration.

[0035] Figure 1 is a graph showing the effect of the addition of chemicals used in this embodiment on the relationship between granulated particle size and moisture content. Here, the polymer flocculant used was Kurita Water Industries Ltd.'s Crisat® C333L. Chemical addition level 1 was set to a chemical addition amount of 0.4% by mass relative to the moisture content at 7.5% by mass. Chemical addition level 2 was set to a chemical addition amount of 1.0% by mass relative to the moisture content at 7.5% by mass. The sintering raw materials were the same except for the chemical addition. Regardless of whether or not chemicals were added, the harmonic mean diameter of the granulated particles increased with increasing moisture content within the moisture content range shown in Figure 1. However, at a moisture content of 12% by mass, the harmonic mean diameter was significantly smaller in the case without chemical addition than in the case with chemical addition, due to the presence of an excessive water film that made granulated particle formation difficult. In the case with chemical addition, it is believed that the moisture was effectively used for granulation without forming a water film.

[0036] Figure 2 is a graph showing the results of measuring the J.P.U. of the granulated particles prepared as described above in a test firing furnace, and organizing the results by moisture content to confirm the influence of chemical addition. The higher the moisture content, the lower the airflow resistance and the greater the airflow rate at the same back pressure. When no chemicals were added, the moisture content peaked at 7.5%, and the moisture content decreased during firing at both low and high moisture contents, as in the results of Figure 7. The moisture content of 6% was lower at both chemical addition levels 1 and 2 than without chemical addition. Meanwhile, at chemical addition level 1, the moisture content was higher than without chemical addition at moisture contents above the granulation limit moisture content of 7.5% or more. At chemical addition level 2, no decrease in the moisture content was observed even at moisture contents exceeding 10% by mass.

[0037] The permeability index is defined as the flow rate of gas passing through a raw material layer of a certain thickness per unit area when there is a certain suction negative pressure gradient. Boyce et al. defined the permeability index BPU (Bed Permeability Unit) in pounds. Currently, in Japan, the permeability index JPU (Japan Permeability Unit) is used, which is expressed by the following formula (1) and converted into CGS units. The permeability index JPU of raw materials is at the level of 20-60, and the permeability index JPU during firing is at the level of 10-30. Formula (1) JPU = (F / A) x (h / s) ｎ Where, JPU: Permeability index, F: Flow rate m ３ / min, A: area m ２ , h: layer thickness (mm), s: negative pressure (mm water column), n: index. n is a value that varies in the range of 0.5<n<1.0 depending on the flow conditions, and in many measurement examples for iron ore sintering, n = 0.6 on average. When n = 1, it is laminar flow, and when n = 0.5, it is turbulent flow, which indicates that the ventilation in the sintered bed has a strong turbulent flow element.

[0038] Figure 3 is a graph showing the results of examining the effects of moisture content and chemical addition by similarly filling a test firing furnace with granulated particles and determining the firing time from the temperature change during firing. The firing time was determined from the time when the thermometer directly above the surface of the raw material in the test device began to rise in temperature to the time when the thermometer at the bottom of the device observed a drop in temperature. When no chemicals were added, it can be seen that the firing time was extended along with a decrease in the air permeability index. It can also be seen that the addition of chemicals reduced the extension of the firing time even when the moisture content increased. In particular, when the moisture content exceeded 10%, the firing time for level 2 was shorter than that for level 1.

[0039] Figure 4 is a graph showing the results of calculating the sinter ore production rate of an actual machine based on the results of the firing test. It can be seen that adding chemicals can suppress the decline in sinter productivity due to excess moisture. In particular, increasing the amount of chemicals added as the moisture content increases is effective in terms of sinter productivity. Figure 5 is a graph showing the relationship between the sinter ore production rate of an actual machine and the chemical concentration relative to the moisture content. Increasing the chemical concentration can ensure productivity at high moisture levels. Figure 6 shows the relationship between the percentage of productivity at an appropriate moisture content of 7.5% and the chemical concentration relative to the moisture content. At an unmodified chemical concentration of 0%, the production rate was only in the 10% range compared to the appropriate moisture content. However, increasing the chemical concentration relative to the moisture content improved the production rate to the appropriate moisture content level.

[0040] Based on the above results, the powder property modification method according to this embodiment involves granulating and heating one or more hydrated bulk materials selected from ore, coal, and limestone, and then adding a chemical agent containing one or more of a polymer flocculant, an inorganic flocculant, and a polymeric water absorbent as a main component to the hydrated bulk materials before granulation, adjusting the amount of chemical agent added depending on the moisture content of the hydrated bulk materials. When the moisture content of the hydrated bulk materials exceeds the granulation limit that reduces air permeability during heating, it is preferable to increase the amount of the chemical agent's active ingredient added as the excess moisture increases. The above example describes a method for producing sintered ore as an example of granulating and heating one or more hydrated bulk materials selected from ore, coal, and limestone. The method can also be applied to methods for producing pellets and coke using ore, coal, limestone, and other raw materials in addition to sintered ore.

[0041] The specified requirements are described in detail below. [Chemical Agent Mainly Containing One or More Selected from Polymer Flocculants, Inorganic Flocculants, and Polymeric Water Absorbents] In this embodiment, a chemical agent mainly containing one or more selected from polymer flocculants, inorganic flocculants, and polymeric water absorbents is used. From the viewpoint of chemical addition efficiency and dispersibility, it is preferable to use a dilution, solution, or dispersion in which the chemical agent is diluted, dissolved, or dispersed in an aqueous or organic solvent or dispersion medium as the chemical solution (chemical). Here, an "aqueous or organic" solvent or dispersion medium refers to a solvent or dispersion medium that "contains 50% or more by mass of water or an organic compound." Examples include water containing 1% by mass of a surfactant, and alcohol (organic compound) containing 30% by mass of water.

[0042] The main component is one that generates adsorption activity in the powder through electrostatic forces or hydrogen bonds of the polymer, resulting in inter-powder bridging. Any main component can be used as long as it has the effect of forming a solidified structure and coagulating particles (aggregates). For example, organic coagulants in powder, granular, or liquid form are suitable. Polyacrylamide-based (copolymerized acrylamide and sodium acrylate), polyvinylamidine-based, and amphoteric polymer-based coagulants are preferred because they not only coagulate but also coagulate. Known inorganic coagulants (e.g., aluminum sulfate, polyaluminum chloride, sodium aluminate, ferric chloride, ferrous sulfate, aluminum sulfate), organic coagulants, and polymeric water absorbents may also be used in combination.

[0043] Furthermore, acrylic acid or acrylamide cationic polymers, methacrylic acid polymers, methacrylic acid aminoester cationic polymers, amidine polymers, anionic W / O type emulsion polymers, etc. can also be used.

[0044] In this embodiment, a chemical agent containing one or more of a polymer flocculant, an inorganic flocculant, and a polymer water absorbent as the main component generally refers to a chemical agent containing at least one of a polymer flocculant, an inorganic flocculant, and a polymer water absorbent in an amount greater than or equal to the amount generally recognized to have a flocculating effect. One example is a chemical agent containing at least 20% by mass of a polymer flocculant. Of course, a chemical agent containing 100% of the main component may be used as is.

[0045] When the drug is solid or diluted for use, the solvent or dispersant can be water or an organic liquid, and the solute or dispersant can be, for example, a polymer composed of C, H, N, and O. Examples of organic liquids include hydrocarbon solvents, that is, compounds composed of C and H, or C, H, and other elements. Using a low-viscosity organic liquid as the solvent or dispersant has the advantage of improving dispersion in bulk materials.

[0046] [Powder Property Modification Effect] In this embodiment, the powder property modification method involves granulating wet bulk materials such as ore, coal, and limestone. A predetermined amount of an active ingredient of a chemical agent, primarily composed of one or more selected from polymer flocculants, inorganic flocculants, and polymeric water absorbents, is added to the bulk material prior to granulation. The cross-linked structure formed between the chemical agent and the powder constituting the loose material retains moisture within the loose material and controls the shape or movement of moisture within the loose material. The mechanisms by which various problems arising from moisture-related properties, such as adhesion and flowability, are resolved during granulation of wet powders are thought to be as follows: The chemical agent retains moisture in the gaps between the loose material, preventing free flow; the layer of the loose material is polarized into water-filled and void areas; and the powder is agglomerated by the water and chemical agent, resulting in secondary particles (agglomeration) and voids not filled with water. In particular, the formation of a water film in the gaps between the granulated particles, which inhibits breathability, can be prevented.

[0047] Furthermore, not only does the crosslinked structure retain the moisture in the bulk material, but the free flow of moisture can also be suppressed, and the fluidity of the powder can also be suppressed, by the moisture forming compounds, increasing viscosity, being retained in the polymer absorbent, and particles flocculating due to the addition of an electric charge by the inorganic flocculant. Furthermore, the powder can be made into secondary particles (agglomerates) by the moisture and chemicals, creating voids, resulting in a so-called "well-drained" state, allowing some of the moisture to flow down through the bulk material layer, thereby mitigating various problems caused by moisture-related properties such as adhesion and fluidity.

[0048] Methods for measuring the moisture content of loose produce include a neutron moisture meter, an electrical resistance moisture meter, a continuous infrared moisture meter, and observation of color, etc. using image analysis.

[0049] The method of adding a predetermined amount of the active ingredient of the drug relative to the moisture content of the loose material can be either adjusting the drug addition rate according to the passing speed of the loose material, or adjusting the ratio of the time the drug is added to the time it is not added, or both.

[0050] The active ingredient of the drug refers to a compound, excluding solvents and dispersants, that has one or more of the following functions: inter-powder bridging, moisture absorption, and particle aggregation. The active ingredient of the drug is preferably added in the range of 0.001 to 0.07% by mass relative to the amount of bulk material. Addition below the lower limit may result in an insufficient amount of moisture retained by inter-powder bridging. On the other hand, addition above the upper limit may result in saturation of the effect, inconsistent uniform dispersion of the drug, and reduced uniformity of the hydrated bulk material. The active ingredient of the drug is preferably added at 0.004% by mass or more, and more preferably 0.05% by mass or less, relative to the amount of bulk material. From the standpoint of granulation, it is preferable to add the active ingredient of the drug at 0.1% by mass to 1% by mass relative to the moisture content of the bulk material.

[0051] It is preferable to stir and mix the bulk material during or after the addition of the chemical. Stirring and mixing can be performed using a dedicated stirrer or existing equipment such as a crusher. For example, the chemical can be added on the yard and stirred and mixed using heavy machinery. The chemical can also be added to the bulk material on a conveyor belt, and mixing can be performed by utilizing the impact of the drop in a transfer chute of the conveyor belt. Stirring and mixing can also be performed using a mixer, kneader, screen, etc. These stirring and mixing methods are expected to improve the diffusibility of the chemical into the powder and improve the modification effect. In this case, when stirring and mixing is performed by transferring between conveyor belts, the effect of modifying the powder properties increases with the number of transfers, at least one transfer, up to about six transfers.

[0052] When adding a drug, if the active ingredient of the drug is a solid (solid material), it is preferable to disperse or dissolve the active ingredient in water or an organic liquid to form a dispersion or solution. Liquid drug substances can also be diluted and used. Adding a liquid to the bulk product improves the handling and addition efficiency of the drug and improves the dispersibility of the drug in the powder that makes up the bulk product. When dispersed or dissolved in water or an organic liquid, the dispersibility of the drug in the powder that makes up the bulk product is improved whether the active ingredient of the drug that was solid remains solid or whether some or all of it becomes liquid and forms a suspension (emulsion).

[0053] Even when the active ingredient of the drug is liquid, by diluting, dispersing or dissolving the active ingredient in water or an organic liquid to form a dilution, dispersion or solution, the drug can be added as a solution with a lower viscosity than the active ingredient of the drug, and evaporation of the active ingredient of the drug due to vaporization can be suppressed, thereby improving the addition efficiency and improving the dispersibility of the drug in the powder that makes up the bulk material.

[0054] Even when the active ingredient of the drug is in a gaseous state, dispersing or dissolving the active ingredient of the drug in water or an organic liquid to form a dispersion or solution can prevent the active ingredient of the drug from dissipating, thereby improving the efficiency of addition.

[0055] When the active ingredient of a drug is diluted, dispersed, or dissolved in water or an organic liquid, the concentration, expressed as the ratio of the active ingredient mass to the sum of the active ingredient mass and the liquid mass, is preferably 5 to 60% by mass, and more preferably 10 to 45% by mass. By setting the active ingredient concentration in the drug at or above the lower limit, the adverse effects of the liquid used to dilute, dissolve, or disperse the drug, such as fluidization of the bulk material, are reduced, thereby improving the efficacy of the drug. By setting the active ingredient concentration in the drug at or below the upper limit, the viscosity of the dilution, dispersion, or solution in which the active ingredient of the drug is diluted, dispersed, or dissolved in water or an organic liquid is further reduced. This effect further improves the penetration rate of the drug into the bulk material layer, further reducing uneven distribution of the drug.

[0056] In this embodiment, it is preferable to add an aqueous or organic liquid separately from the chemical agent when adding or stirring the chemical agent to the bulk product, as this improves the dispersibility of the active ingredient of the chemical agent in the powder that makes up the bulk product.

[0057] According to the powder property modification method and sintered ore manufacturing method of the present invention, when granulating and heating the hydrated bulk material, a flocculant or water absorbent is added depending on the moisture content of the bulk material, thereby preventing deterioration of breathability during heating due to excessive moisture. This shortens the heating time and improves productivity, making it industrially useful. Furthermore, the powder property modification method of the present invention can be used to manufacture granulated materials such as sintered ore, reduced iron, and pellets.

[0058] 1. Iron ore powder 2. Water 3. Water film 4. Water droplets

Claims

1. A method for modifying powder properties, in which, when granulating and heating moistened loose material, an agent containing one or more of a polymer flocculant, an inorganic flocculant, and a polymer water-absorbing material as a main ingredient is added to the moistened loose material before or during the granulation process, and the amount of the agent added is adjusted according to the moisture content of the moistened loose material or an operational index correlated with the moisture content of the moistened loose material.

2. The method for modifying powder properties according to claim 1, wherein the hydrated bulk material is at least one of ore, by-product slag from ore refining or steel manufacturing, and by-products from petroleum distillation and rectification.

3. A method for producing sintered ore by granulating and heating sintering raw materials containing iron-containing raw materials, carbon-containing raw materials, and CaO-containing raw materials as hydrated bulk materials, the method comprising: a powder property modification process for adjusting the amount of the chemicals to be added according to the moisture content of the sintering raw materials or an operational index correlated with the moisture content of the hydrated bulk materials, in accordance with the powder property modification method described in claim 1 or 2; a granulation process for granulating the sintering raw materials whose properties have been modified in a granulator; and a sintering process for sintering the granulated sintering raw materials in a sintering machine.

4. A method for producing sintered ore as described in claim 3, wherein the amount of chemicals added in the powder property modification step is adjusted according to the permeability index in the sintering step or an operating condition index correlated with permeability.

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