Method for modifying the properties of powder 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

Technical Field

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

Background Art

[0002] Powders and granules such as various ores, by-products during ore refining and steel manufacturing, and by-products during distillation and rectification of petroleum are called bulk materials. Bulk materials often contain fine powder. Therefore, granulation, firing, and adjustment to a predetermined particle size are performed to obtain raw materials. In the iron and steel industry, powdered iron ore is mixed with limestone and powdered coke, and granulated into pseudo-particles of a predetermined size after adding water. It is known that pseudo-particles adjusted to an appropriate size and properties are supplied to a sintering machine, ensuring air permeability and improving the productivity of sintered ore.

[0003] On the other hand, bulk materials are stored in open yards or exposed to the atmosphere and transported. Then, due to overlapping rainfall, the bulk materials will hold high moisture. Such a state is called a hydrous bulk material. When granulating such a hydrous bulk material, it is known that it is necessary to manage an appropriate amount of moisture. Granulated products with excessive moisture reduce air permeability, deteriorate the productivity of the granulated products, and cause quality degradation. On the other hand, excessive equipment investment is required for moisture removal. For example, a method such as mixing dry raw materials stored in a silo or the like in advance can also be used.

[0004] Conventionally, methods as disclosed in Patent Documents 1 to 3 have been adopted to address such problems.

[0005] Patent Document 1 discloses a method for processing sintering raw materials that suppresses the adhesion of low-alumina-containing ores to each other, uniformly mixes high-alumina-containing ores and low-alumina-containing ores, and suppresses the uneven distribution of alumina. The technology involves adding an adhesion inhibitor to the low-alumina-containing ore during granulation to obtain a blending powder in which at least the low-alumina-containing ore and the high-alumina-containing ore are uniformly dispersed.

[0006] Patent Document 2 discloses a method for treating water-containing bulk materials to eliminate loading problems on a belt conveyor caused by slurry-like seepage that inevitably occurs during the loading of water-containing bulk materials. This technology improves handling performance by suppressing the generation of seepage during loading of bulk materials by attaching a flocculant to the water-containing bulk materials.

[0007] Patent Document 3 discloses a technology that involves adding a flocculant or water-absorbing material to water-containing bulk material to retain moisture in the powder, thereby suppressing equipment stoppage due to adhesion, blowout or backflow during transport, and collapse of storage piles. When applied to a granulation method for sintering raw materials, it is said that the solidification of small-particle water-containing bulk material while unevenly distributed is suppressed, so the strength of the granulated material does not decrease, leading to improved yield during sintering, uniformity of mineral structure, and increased productivity. [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] Japanese Patent Publication No. 2017-125247 [Patent Document 2] International Publication No. 2015 / 151524 [Patent Document 3] International Publication No. 2024 / 004298 [Overview of the project] [Problems that the invention aims to solve]

[0009] However, the above-mentioned conventional technologies had the following problems. For example, when the water-containing bulk raw material contains excessive moisture, the measure of mixing it with dry raw material stored in silos has the problem that the size of the silos is limited, the period that can be addressed is short, and the effect is limited. The measure of reducing the moisture content by storing all the raw materials used in a covered space for a long period of time presents problems in terms of securing land required for the construction of the necessary building and the increase in equipment costs.

[0010] Furthermore, Patent Document 1 does not address the perspective of controlling the concentration of the chemical agent to contribute to the productivity of sintered ore. There is a problem in that it does not cover application to single brands or brands with no difference in alumina content.

[0011] Furthermore, the technology described in Patent Document 2 focuses primarily on the handling properties of the powder and does not consider the productivity of sintering or the correlation between granulation and air permeability. In addition, the technology described in Patent Document 3 only states that it contributes to improving the productivity of sintering, and does not consider the appropriate concentration of the chemical agent.

[0012] These conventional technologies have been insufficient in addressing the aeration obstruction caused by water itself in operating areas exceeding the optimal moisture content for granulation, whether due to raw material origins or rainfall at steel mills. This technology improves sintering productivity or quality by improving aeration in moisture levels higher than the optimal moisture content for granulation, which these existing technologies cannot address.

[0013] This invention has been made in view of the above circumstances, and aims to propose a powder property modification technology that enables productive heating during heating processes, from granulating water-containing bulk materials and heating to evaporate water, to high-temperature heating processes involving reactions such as calcination. In particular, this invention achieves improved permeability in the high-moisture range, which cannot be addressed by conventional technologies, and aims to propose a method for producing sintered ore with improved productivity using water-containing bulk materials as raw materials. [Means for solving the problem]

[0014] The present invention provides a method for modifying the properties of powders that advantageously solves the above problems. This method involves granulating a water-containing bulk material and heating it, and adding a chemical agent mainly composed of one or more selected from polymer flocculants, inorganic flocculants, and polymer water absorbents to the water-containing bulk material before granulation or during the granulation process. The method is characterized by adjusting the amount of the chemical agent added according to the water content of the water-containing bulk material or an operational indicator correlated with the water content of the water-containing bulk material.

[0015] Furthermore, a more preferable solution for the powder property modification method according to the present invention is that the water-containing bulk material is at least one of the following: ore, by-product slag from ore refining or steel manufacturing, and by-products from petroleum distillation and rectification.

[0016] The present invention provides a method for producing sintered ore that advantageously solves the above problems, comprising: a powder property modification step in which the amount of the agent added is adjusted according to the moisture content of the sintered raw material or an operational indicator correlated with the moisture content of the moisture-containing bulk material, in accordance with any of the above powder property modification methods; a granulation step in which the sintered raw material whose properties have been modified is granulated in a granulator; and a sintering step in which the granulated sintered raw material is sintered in a sintering machine.

[0017] Furthermore, a more preferable solution for the sintering ore manufacturing method according to the present invention is to adjust the amount of chemical added in the powder property modification step according to the permeability index in the sintering step, or an operating condition index correlated with permeability. [Effects of the Invention]

[0018] According to the powder property modification method of the present invention, when granulating and heating a water-containing bulk material, a flocculant or water-absorbing material is added according to the moisture content of the bulk material, thereby suppressing the deterioration of air permeability during heating due to excessive moisture. This has the effect of preventing the resulting decrease in productivity. In addition, the homogenization of the product can be obtained by improving the diffusibility of the raw material. [Brief explanation of the drawing]

[0019] [Figure 1] It is a graph showing the influence of chemical agent addition on the relationship between the harmonic mean diameter and the moisture content of granulated particles when granulating sintering raw materials. [Figure 2] It is a graph showing the influence of chemical agent addition on the relationship between the air permeability index and the moisture content when heating granulated particles. [Figure 3] It is a graph showing the influence of chemical agent addition on the relationship between the heating time of granulated particles and the moisture content. [Figure 4] It is a graph showing the influence of chemical agent addition on the relationship between the productivity of sintered ore and the moisture content of granulated particles. [Figure 5] It is a graph showing the relationship between the chemical agent concentration with respect to the moisture content and the sintered ore production rate of an actual machine. [Figure 6] It is a graph showing the relationship between the ratio with respect to the productivity at the appropriate moisture value and the chemical agent concentration with respect to the moisture content. [Figure 7] (a) A graph showing the relationship between the added moisture content, the harmonic mean diameter of granulated particles, and the air permeability during heating when granulating sintering raw materials, and (b) a schematic diagram of the particle morphology.

Mode for Carrying Out the Invention

[0020] Hereinafter, embodiments of the present invention will be specifically described. Also, the following embodiments illustrate methods for embodying the technical idea of the present invention and do not specify the configuration to be the following. That is, the technical idea of the present invention can be variously modified 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. Suitable equipment for the sintered ore production method according to this embodiment includes a chemical additive facility, a granulator, and a sintering facility. The sintering facility includes a sintering machine, a crusher, and a control device. In this embodiment, examples of bulk materials that are hydrated include ore, by-product slag from ore refining and steel production, and by-products from petroleum distillation and rectification. Examples of ore include iron ore, coal, limestone, dolomite, silica, magnesite and other MgO sources, and nickel and manganese ore.

[0022] In the chemical additive equipment, it is preferable to spray liquid chemicals or scatter powdered chemicals, and then mix the powdered bulk material with a dedicated agitator. Instead of a dedicated agitator, agitation using a crusher or heavy machinery, or the impact from the drop difference when transferring between belt conveyors may be used. This agitation promotes the diffusion of the chemicals into the powder. This process constitutes the powder property modification process.

[0023] A granulator granulates sintering raw materials containing iron, carbon, and CaO to form granulated particles. During the granulation process, granulation water is added to the sintering raw materials. This process constitutes the granulation stage. The granulated particles produced by the granulator are then transported to a sintering machine. Iron-containing raw materials include, for example, iron ore or dust generated within steel mills. Carbon-containing raw materials include, for example, powdered coke or anthracite. CaO-containing raw materials include, for example, quicklime, limestone, or slag. Other necessary components may be added.

[0024] The sintering machine is, for example, a Dwight-Loyd type sintering machine. The sintering machine comprises a raw material supply device, a pallet, a cutoff plate, an ignition furnace, a gaseous fuel supply device, and a window box. The raw material supply device loads granulated particles into the pallet.

[0025] The pallet is an endlessly moving pallet. When granulated particles are charged into the pallet from the raw material supply device, a charging layer of sintering raw material is formed within the pallet. The cutoff plate levels the surface of the charging layer and adjusts its thickness to a predetermined target thickness. This process constitutes the charging layer formation step.

[0026] The ignition furnace is located downstream of the raw material supply device and ignites the carbon-containing raw material contained in the surface layer of the charge bed. The gaseous fuel supply device supplies gaseous fuel to the surface layer of the charge bed. For example, city gas (LNG) is supplied as the gaseous fuel. The gaseous fuel supplied from the gaseous fuel supply device is not limited to city gas; 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 mixtures thereof may be used.

[0027] A window box is installed below the pallet and draws air downwards from within the charging layer formed inside the pallet. When air is drawn downwards by the window box, the combustion and molten zones within the charging layer move downwards. Also, as the air is drawn downwards, the gaseous fuel supplied from the gaseous fuel supply device is introduced into the charging layer from the surface. As the pallet moves, the combustion and molten zones within the charging layer move downwards, causing the sintering material in the charging layer to be sintered. A sintered cake is obtained by sintering the sintering material. This process is the sintering step.

[0028] The crusher crushes the sintered cake discharged from the sintering machine to obtain crushed sintered cake material. The crushed sintered cake material is cooled and sized to produce sintered ore. This process constitutes the crushing step. The above-mentioned charging layer formation step, sintering step, and crushing step together constitute the sintering process.

[0029] The control device is a general-purpose computer, such as a workstation or personal computer, having a control unit and a memory unit. The control unit is, for example, a CPU, which controls the operation of the chemical dosing equipment, granulator, sintering machine, and crusher by executing programs read from the memory unit. The memory unit is, for example, an information recording medium such as a flash memory that can be updated, a hard disk that is built-in or connected via a data communication terminal, or a memory card, and a device for reading and writing to such a medium. The memory unit stores programs for the control unit to perform each function, as well as data used by those programs.

[0030] The control unit calculates, for example, the air permeability index of the sintering raw materials stacked on the pallet, based on the suction airflow 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 a granulator, the control unit modifies the granulation conditions so that the distribution width of the particle size distribution of the granulated particles becomes narrower. When the distribution width of the particle size distribution of the granulated particles becomes narrower, the packing density of the granulated particles charged into the pallet decreases, and the charging density of the charging layer 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 into 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 blended into the sintering raw material. Since CaO functions as a binder, it causes ungranulated powder, which is difficult to granulate, to adhere to the granulated particles, reducing the amount of fine particles in the particle size distribution. For this reason, 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 changing the granulation conditions.

[0033] When adjusting the amount of chemical added, the control unit adjusts the amount of chemical added so that the permeability index of the granulated particles during heating approaches a predetermined value. The amount of chemical added to bring the permeability index, or an operating condition index correlated with permeability, closer 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 it according to that value. The heat exchangeability index can also be used as an operating condition correlated with permeability. In sintering production, indices such as those used in the pre-drying process of coal for coke raw materials, which involves gas-solid or gas-liquid heat exchange between high-temperature gas and the target powder or water, can be used.

[0034] <Granulation and moisture content> Figure 7 schematically shows the effect of moisture content on granulated particle size and permeability during heating when granulating sintering raw materials. In the water absorption region shown in Zone I, moisture 2 is absorbed by the sintering raw material, especially the powdered iron ore 1, resulting in small granulated particle size and small gaps between granulated particles, thus low permeability during heating. In the granulation region shown in Zone II, moisture 2 that was not absorbed by the powdered iron ore 1 appears on the surface of the powdered iron ore, causing the powdered iron ore particles to adhere to each other and promoting granulation. As a result, the granulated particle size increases, the gaps between granulated particles widen when stacked, and permeability during heating improves. In the excess moisture region of Zone III, the excess moisture exists as liquid water (water film 3) in the gaps between granulated particles, inhibiting permeability when stacked. In the example in Figure 7, the granulation limit moisture content is approximately 7.5% by mass. In Zone IV, where there is an even greater excess of water, the iron ore powder 1 floats within the water droplets 4, resulting in a slurry-like state, which leads to smaller granulation and poorer aeration.

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

[0036] Figure 2 is a graph showing the results of measuring the air permeability index (JPU) after filling a test firing furnace with the granulated particles prepared above, organized by moisture content, to confirm the effect of chemical additives. A higher air permeability index indicates lower airflow resistance and greater airflow at the same back pressure. When no chemicals were added, similar to the results in Figure 7, the air permeability index during firing decreased at both low and high moisture content, peaking at 7.5% moisture content. At a moisture content of 6%, the air permeability index was lower than without chemical additives at both chemical additive levels 1 and 2. On the other hand, at chemical additive level 1, the air permeability index was higher than without chemical additives at moisture content above the granulation limit moisture content of 7.5% or higher. At chemical additive level 2, no decrease in the air permeability index was observed even at moisture content exceeding 10% by mass.

[0037] The air permeability index is defined as the gas flow rate passing through a raw material layer of a certain layer thickness per unit area at a place with a pressure gradient of a certain suction negative pressure. Voice et al. defined the bed permeability unit BPU in pounds. Currently in Japan, the JPU (Japan Permeability Unit) expressed by the following formula (1) and converted to CGS units is used. The air permeability index JPU of the raw material is at a level of 20 - 60, and the air permeability index JPU during firing is at a level of 10 - 30. Formula (1) JPU=(F / A)×(h / s) n Here, JPU: air permeability index, F: flow rate m 3 / min, A: area m 2 , h: layer thickness mm, s: negative pressure mm water column, n: represents an index. n is a value that changes within the range of 0.5 < n < 1.0 depending on the flow state. In many measurement examples for iron ore sintering, on average, n = 0.6. When n = 1, it is laminar flow, and when n = 0.5, it is turbulent flow. Therefore, it shows that the turbulence element is strong in the ventilation within the sintering layer.

[0038] Figure 3 is a graph of the results of similarly filling granulated particles into a test firing furnace, determining the firing time from the temperature change during firing, and examining the effects of moisture content and chemical agent addition. The time from when the thermometer directly above the raw material surface of the test apparatus starts to rise in temperature to the timing when the thermometer at the lower part of the apparatus observes a decrease from the temperature rise is defined as the firing time. When no chemical agent is added, it can be seen that the firing time extends as the air permeability index decreases. It can be seen that the extension of the firing time is reduced even when the moisture content increases due to the addition of the chemical agent. In particular, when the moisture content exceeds 10%, the firing time at level 2 is shorter than that at level 1.

[0039] Figure 4 is a graph showing the calculated sintered ore production rate of the actual machine based on the above firing test results. It can be seen that adding chemicals can suppress the decrease in sintered ore productivity due to excess moisture. In particular, it can be seen that increasing the amount of chemicals added along with the moisture content is effective in terms of sintered ore productivity. Figure 5 is a graph showing the relationship between the sintered ore production rate of the actual machine and the chemical concentration as a percentage of moisture content. By increasing the chemical concentration, it is possible to ensure a high production rate even at high moisture content. Figure 6 shows the relationship between the percentage of productivity at an appropriate moisture content of 7.5% and the chemical concentration as a percentage of moisture content. It is shown that with an unmodified chemical concentration of 0%, the production rate is only in the teens compared to the production rate at the appropriate moisture content, but by increasing the chemical concentration as a percentage of moisture content, it can be improved to the production rate at the appropriate moisture content level.

[0040] From the above results, the powder property modification method according to this embodiment involves granulating one or more water-containing bulk materials selected from ore, coal, and limestone, and heating them. Before granulation, an agent mainly composed of one or more selected from polymer flocculants, inorganic flocculants, and polymer water absorbents is added to the water-containing bulk materials, and the amount of the agent added is adjusted according to the moisture content of the water-containing bulk materials. When the moisture content of the water-containing bulk materials exceeds the granulation limit that reduces permeability during heating, it is preferable to increase the amount of the active ingredient of the agent added in proportion to the increase in excess moisture content. In the above explanation, the method for producing sintered ore was used as an example of granulating one or more water-containing bulk materials selected from ore, coal, and limestone and heating them. The method is also applicable to the production of pellets and coke using ore, coal, and limestone as raw materials other than sintered ore.

[0041] The following details the identified requirements. [An agent whose main component is one or more selected from polymer flocculants, inorganic flocculants, and polymer water absorbents] In this embodiment, a drug mainly composed of one or more selected from polymer flocculants, inorganic flocculants, and polymer water absorbents is used. From the viewpoint of drug addition efficiency and dispersibility, it is preferable to use a diluted solution, solution, or dispersion obtained by diluting, dissolving, or dispersing the drug in an aqueous or organic solvent or dispersion medium as the drug solution (pharmaceutical). Here, the "aqueous or organic" solvent or dispersion medium is a solvent or dispersion medium that "contains 50% by mass or more of water or an organic compound," for example, water containing 1% by mass of a surfactant, or an alcohol (organic compound) containing 30% by mass of water.

[0042] Furthermore, the main component used is one that exhibits adsorption activity to the powder through the electrostatic force or hydrogen bonding of the polymer, thereby causing crosslinking between powder particles. Any main component that has the effect of forming a solid granular structure and creating agglomerated particles (aggregates) can be used. For example, powdered, granular, or liquid organic flocculants are preferably used. Polyacrylamide-based (a copolymer of allylamide and sodium acrylate), polyvinyl amidine-based, and amphoteric polymer-based flocculants are preferred because they exhibit not only a coagulation effect but also an agglomerating effect. In addition, known inorganic flocculants (aluminum sulfate, polyaluminum chloride, sodium aluminate, ferric chloride, ferrous sulfate, aluminum sulfate, etc.), organic flocculants, and polymeric water-absorbing materials may be used in combination.

[0043] Furthermore, acrylic acid-based or acrylamide-based cationic polymers, methacrylic acid-based polymers, methacrylic acid amino ester cationic polymers, amidine polymers, and anionic W / O type emulsion polymers can also be used.

[0044] In this embodiment, "main component being one or more selected from polymer flocculants, inorganic flocculants, and polymer water absorbents" refers to a drug containing one or more of these selected from polymer flocculants, inorganic flocculants, and polymer water absorbents in an amount generally recognized as having a flocculating effect. One example is a drug containing approximately 20% by mass or more of polymer flocculants. Of course, a drug with 100% of the main component can also be used as is.

[0045] When the drug is in solid form or is used diluted, the solvent or dispersion medium can be water or an organic liquid, and the solute or dispersed phase 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 a solvent or dispersion medium has the advantage of improving dispersion in bulk materials.

[0046] [Effect of modifying the properties of powder] The powder property modification method of this embodiment involves adding a predetermined amount of an active ingredient of a chemical agent, primarily composed of one or more selected from polymer flocculants, inorganic flocculants, and polymer water absorbents, relative to the amount of bulk material, before granulation of water-containing bulk materials such as ore, coal, and limestone. This agent creates a cross-linked structure between the chemical agent and the powder constituting the bulk material, which retains moisture within the bulk material and controls the form or movement of moisture within the bulk material. The mechanism by which various problems arising from properties such as adhesion and fluidity caused by moisture during granulation of water-containing powders are solved is thought to be as follows: Moisture is retained in the gaps between the bulk material by the chemical agent, preventing the moisture from flowing freely; the bulk material layer becomes polarized into water-filled portions and voids; and the powder undergoes secondary particle formation (clumping) due to moisture and the chemical agent, creating voids that are not filled with water. In particular, it can suppress the formation of a water film in the gaps between granulated particles, which hinders air permeability.

[0047] Furthermore, the aforementioned cross-linked structure not only retains moisture within the bulk material, but it can also suppress the free flow of moisture and inhibit the flowability of the powder by preventing moisture from forming compounds, increasing viscosity, retaining moisture in the polymer absorbent, and causing particles to aggregate due to the imparting of charge by the inorganic flocculant. In addition, the powder may undergo secondary particle formation (clumping) due to moisture and chemicals, creating voids and resulting in a state of "good drainage." This allows some of the moisture to flow down within the bulk material layer, mitigating various problems caused by moisture-related properties such as adhesion and flowability.

[0048] Methods for measuring the moisture content of bulk materials include "neutron moisture meters," "electrical resistance moisture meters," "continuous infrared moisture meters," and "observation of color, etc., by image analysis."

[0049] The method of adding a predetermined amount of the active ingredient of the drug relative to the moisture content of the bulk material can be achieved by either adjusting the rate of drug addition according to the passage speed of the bulk material, adjusting the ratio of drug addition time to non-addition time, or both.

[0050] The active ingredient of a drug refers to a compound that, excluding the solvent and dispersion medium, possesses one or more of the following properties: inter-particle crosslinking, moisture absorption, and particle aggregation. It is preferable to add the active ingredient of the drug in an amount of 0.001 to 0.07% by mass relative to the amount of bulk material. Adding below the lower limit may result in insufficient moisture retention due to inter-particle crosslinking. On the other hand, adding above the upper limit may lead to saturation of the effect, and the drug may not be uniformly dispersed, potentially reducing the uniformity of the water-containing bulk material. Preferably, the active ingredient of the drug is added at a rate of 0.004% by mass or more, and preferably 0.05% by mass or less, relative to the amount of bulk material. On the other hand, from the viewpoint of granulation, it is preferable to add 0.1% to 1% by mass of the active ingredient of the drug relative to the moisture content of the bulk material.

[0051] It is preferable to stir and mix the bulk material when adding the chemical agent or after adding it. Stirring and mixing can be done using dedicated stirrers or existing equipment such as crushers. For example, the chemical agent can be added in the yard and stirred and mixed using heavy machinery. The chemical agent can also be added to the bulk material on a conveyor belt and mixed using the impact of the drop at the transfer chute of the conveyor belt. Stirring and mixing can also be done using stirrers, kneaders, screens, etc. Stirring and mixing in these ways is expected to improve the diffusivity of the chemical agent to the powder and enhance the modification effect. In this case, when stirring and mixing by transferring conveyor belts, the effect of modifying the powder properties increases with the number of transfers, from a minimum of one transfer to about six transfers.

[0052] When adding a drug, if the active ingredient of the drug is a solid, it is preferable to disperse or dissolve the active ingredient in water or an organic liquid to form a dispersion or solution. Liquid drugs can also be diluted before use. Adding a liquid to bulk materials improves the handling and addition efficiency of the drug, and also improves the dispersibility of the drug into the powders constituting the bulk material. When dispersed or dissolved in water or an organic liquid, even if the active ingredient of the drug, which was a solid, remains solid, or if some or all of it becomes liquid and forms a suspension (emulsion), the dispersibility of the drug into the powders constituting the bulk material is improved.

[0053] Even when the active ingredient of a drug is a liquid, diluting, dispersing, or dissolving it in water or an organic liquid to form a diluted solution, dispersion, or solution allows the drug to be added as a solution with lower viscosity than the active ingredient itself. Furthermore, evaporation due to vaporization of the active ingredient can be suppressed, thereby improving the efficiency of addition and enhancing the dispersibility of the drug into the powders constituting the bulk material.

[0054] Even if the active ingredient of a drug is in gaseous form, dispersing or dissolving it in water or an organic liquid to form a dispersion or solution can suppress the dissipation of the active ingredient, thereby improving the efficiency of drug addition.

[0055] When the active ingredient of a drug is diluted, dispersed, or dissolved in water or an organic liquid, the concentration is expressed as the ratio of the mass of the active ingredient to the sum of the mass of the active ingredient and the mass of the liquid. The preferred concentration is 5-60% by mass, and more preferably 10-45% by mass. By setting the active ingredient concentration above the lower limit, the effects of the liquid used for dilution, dissolution, or dispersion of the drug on the bulk material, such as fluidization, are reduced, thereby improving the drug's effectiveness. By setting the active ingredient concentration below the upper limit, the viscosity of the diluted solution, dispersion, or solution obtained by diluting, dispersing, or dissolving the active ingredient in water or an organic liquid is further reduced. This effect improves the penetration rate of the drug into the bulk material layers and further reduces the uneven distribution of the drug.

[0056] Furthermore, in this embodiment, it is preferable to add an aqueous or organic liquid separately from the drug when adding or stirring the drug to the bulk material. This improves the dispersibility of the active ingredient of the drug among the powders constituting the bulk material. [Industrial applicability]

[0057] According to the powder property modification method and sintered ore manufacturing method of the present invention, when granulating and heating water-containing bulk material, a flocculant or water-absorbing material is added according to the moisture content of the bulk material, thereby suppressing deterioration of air permeability during heating due to excessive moisture. As a result, heating time is shortened and productivity is improved, making it industrially useful. Furthermore, the powder property modification method of the present invention can be used in the production of granulated products such as sintered ore, reduced iron, and pellets. [Explanation of Symbols]

[0058] 1. Iron powder ore 2. Moisture 3 Water film 4 water drops

Claims

1. When granulating and heating a hydrated bulk material, When adding a chemical agent mainly composed of one or more selected from polymer flocculants, inorganic flocculants, and polymer water absorbents to the hydrated bulk material before or during the granulation process, the amount of the chemical agent added is adjusted according to the moisture content of the hydrated bulk material, or an operational indicator correlated with the moisture content of the hydrated bulk material. A method for modifying the properties of a powder, wherein when the moisture content of the water-containing bulk material exceeds the granulation limit that reduces permeability when heated, the amount of active ingredient of the drug added is increased in proportion to the increase in the excess moisture content.

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

3. The method for modifying the properties of a powder according to Claim 1, wherein the moisture content of the water-containing bulk material that reduces permeability when heated is 7.5% or more.

4. The method for modifying the properties of a powder according to Claim 1, wherein when the moisture content of the water-containing bulk material exceeds 10%, an amount of the agent greater than or equal to the amount added to maintain the harmonic mean diameter of the granulated particles is added.

5. A method for producing sintered ore, comprising granulating and heating a sintering raw material containing an iron-containing raw material, a carbon-containing raw material, and a CaO-containing raw material as a hydrated bulk material, A powder property modification step in which the amount of the agent to be added is adjusted according to the powder property modification method described in any one of claims 1 to 4, in accordance with the moisture content of the sintering raw material or an operational indicator correlated with the moisture content of the water-containing bulk material, A granulation process in which the sintering raw material whose properties have been modified is granulated using a granulator, The sintering process involves sintering the granulated raw materials for sintering in a sintering machine, A method for producing sintered ore, including the method described above.

6. The method for producing sintered ore according to claim 5, wherein the amount of chemical agent 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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