Method for suppressing equipment failure caused by mineral raw materials

Abstract

To provide a method for suppressing facility disorders due to a mineral raw material by suppressing natural oxidation and heat generation of the mineral raw material having a particular water content and particle diameter during transfer and storage of the mineral raw material and improving handling of the mineral raw material during the transfer and storage.SOLUTION: A method for suppressing facility disorders due to a mineral raw material comprises a contact step of bringing a polymer dispersant into contact with a mineral raw material including 70 wt.% or more of a particle having a water content of 1 to 30 wt.% and a particle diameter of 8 mm or less to obtain a dispersant-containing mineral raw material. In the contact step, the mineral raw material and the polymer dispersant are brought into contact with each other so that a particle diameter of 95 wt.% or more of the polymer dispersant after the contact step is 110% or more and less than 500% relative to an average of the particle diameter of the polymer dispersant before the contact step and a water content of 95 wt.% or more of the dispersant-containing mineral raw material after the contact step is 1 to 12 wt.%.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a method for suppressing equipment failure caused by mineral raw materials. [Background technology]

[0002] Typically, large amounts of coal are piled up, accumulated, and stored in coal yards at power plants, steel mills, mines, etc. Coke, a porous solid composed primarily of carbon produced by carbonizing coal at a high temperature of 1,200°C, is used for steelmaking, casting, fuel, and other purposes, and this coke is also often piled up, accumulated, and stored in coke yards. In addition to the above, iron works and the like also pile up, accumulate, and store raw materials such as lumped iron ore, sintered ore that has been processed from powdered iron ore or powdered limestone to have a particle size and strength suitable for charging into a blast furnace, and steelworks dust and sludge discharged from blast furnaces, converters, electric furnaces, etc. Many of the storage yards (yards) for the above-mentioned coal, coke, limestone, iron ore, sintered ore, steel mill dust, sludge, etc. (hereinafter referred to as "mineral raw materials") are located outdoors. The moisture content of the stored mineral raw materials increases due to rainfall and water spraying to prevent dust buildup. As a result, the surface of the mineral raw materials becomes more sticky, causing problems such as clogging in conveyor belts, combs (regardless of whether they are latticed or mesh) used to remove foreign matter, and hoppers for storing or temporarily placing the materials being transported. Furthermore, adhesion of mineral raw materials to the conveyor belt has also caused problems such as the mineral raw materials falling off at the conveyor's rewinding point. This increased moisture content of the mineral raw materials has led to poor handling of the mineral raw materials, reduced efficiency in facilities used to store and transport the mineral raw materials, and even safety issues.

[0003] Incidentally, in the past, as in a method for transferring iron-making raw materials that improves the handling of slurried iron-making raw materials (Patent Document 1), when the iron-making raw materials turn into a slurry due to rainfall or watering during storage, making it difficult to transport them, it has been known to bring a polymer water absorbent into contact with the iron-making raw material slurry in order to improve the handling of the iron-making raw material slurry. However, when it comes to iron ore raw materials such as coal, coke, iron ore, limestone, sintered ore, and steel mill dust, they are rarely transported in a slurried state, and in most cases, raw steel materials that are not slurried but have a high water content are transported.

[0004] Furthermore, the above-mentioned mineral raw materials may react with oxygen in the air during storage, causing oxidation reactions, resulting in temperature rises and the generation of heat and smoke, which may in some cases lead to fires and other accidents. Therefore, various measures have been taken to suppress these reactions, reduce heat generation, and ensure safe storage. One such measure is to suppress oxidation reactions within the facilities by filling silos and hoppers with inert gases. However, this requires large-scale facilities, which creates problems of time and cost, and simpler measures are therefore desired.

[0005] For example, Patent Document 2 proposes the application of an inhibitor composition to coal as a method for suppressing spontaneous combustion, particularly of low-rank coal lumps. The inhibitor composition is described as containing crude glycerin and a VAE copolymer or a PVA copolymer in a ratio of 90:10 to 10:90. The crude glycerin refers to a by-product derivative from a transesterification reaction involving triglycerides, including transesterification reactions involved in the biodiesel production process. The by-products described include glycerin and at least one component selected from fatty acids, esters, salts, methanol, tocopherol, sterol, monoglycerides, diglycerides, and triglycerides.

[0006] Furthermore, Patent Document 3 describes a coal production method characterized by spraying a glycerin-containing solution, which is a by-product in the biodiesel production process, onto the surface of the coal to suppress low-temperature oxidation. However, with this method, the water contained in the powder evaporates quickly, so the effect is not lasting, and it cannot cope with excessive increases in moisture due to rainfall, resulting in problems such as runoff and the generation of water contaminated by the powder.

[0007] Patent Document 4 discloses a liquid product that uses a water-soluble polymer absorbent mixed with other ingredients for dust prevention. However, its intended use is dust prevention, and it describes spraying the mixed chemical onto the coal surface to form a surface resin layer that prevents dust from scattering, while also having the effect of preventing ignition. However, with regard to preventing spontaneous combustion, the document only mentions the effect of the surface resin layer, and does not provide any specific examples.

[0008] Patent Document 5 also discloses a technology for preventing spontaneous combustion and dust generation by forming a hydrogel layer coating on the surface of a coal pile using a highly water-absorbent polymer, coal, and water, based on the same principle as that of polymer coatings in conventional technology. However, this method does not provide sufficient protection against spontaneous combustion when cracks or damage occur in the surface resin layer due to partial pile transportation.

[0009] Patent Document 6 describes the application of a pyrolysis inhibitor whose main component is urea. A polymeric absorbent is added as an additive to complement the effect of the urea. The combined use of urea and the pyrolysis inhibitor is an essential condition, and ammonia gas is generated during thermal decomposition during use, which means that sufficient effects are not obtained from the perspective of environmental safety. [Prior art documents] [Patent documents]

[0010] [Patent Document 1] Patent No. 6041627 [Patent Document 2] Special Publication No. 2015-512470 [Patent Document 3] Japanese Patent Application Laid-Open No. 2011-195779 [Patent Document 4] Japanese Patent Publication No. 59-025871 [Patent Document 5] Japanese Patent Application Publication No. 05-230480 [Patent Document 6] Japanese Patent Application Laid-Open No. 2005-194447 Summary of the Invention [Problem to be solved by the invention]

[0011] Therefore, for mineral raw materials with high moisture content, handling during transportation is an issue from the viewpoints of safety and efficiency. Also, from the viewpoint of safety, a method for suppressing the problem of mineral raw materials themselves, which have the property of generating heat through oxidation, i.e., a method for suppressing natural oxidation and heat generation during transportation and storage, is also desired.

[0012] In view of the above-mentioned current situation, the present invention aims to provide a method for suppressing equipment damage caused by mineral raw materials by suppressing natural oxidation and heat generation during transportation and storage of mineral raw materials having a specific moisture content and particle size, and improving the handleability of the mineral raw materials during transportation and storage. [Means for solving the problem]

[0013] As a result of intensive research conducted by the inventors to solve the above-mentioned problems, they discovered that rather than simply contacting a mineral raw material having a specific moisture content and particle size with a polymer dispersant having a high water retention capacity, contacting the mineral raw material with a polymer dispersant so that the polymer dispersant after contact has a specific particle size and the mineral raw material after contact has a specific moisture content has a significant effect of suppressing equipment damage caused by the mineral raw material (equipment damage caused by natural oxidation, heat generation, and spontaneous combustion of the mineral raw material, equipment damage caused by adhesion of the mineral raw material to the equipment, etc.), which led to the completion of the present invention.

[0014] In other words, the present invention is a method for suppressing equipment failure caused by mineral raw materials, which includes a contacting step of contacting a mineral raw material having a moisture content of 1 to 30% by weight and containing 70% or more by weight of particles with a particle diameter of 8 mm or less with a polymer dispersant to obtain a dispersant-containing mineral raw material, wherein in the contacting step, the mineral raw material is contacted with the polymer dispersant so that the particle diameter of 95% or more by weight of the polymer dispersant after the contacting step is 110% or more but less than 500% of the average particle diameter of the polymer dispersant before the contacting step, and the moisture content of 95% or more by weight of the dispersant-containing mineral raw material after the contacting step is 1 to 12% by weight. In the method for suppressing equipment failure of the present invention, the average particle size of the polymer dispersant before the contact step is preferably 5 to 1400 μm. In the method of the present invention, the equipment damage caused by the mineral raw materials is preferably at least one selected from the group consisting of spontaneous combustion of the mineral raw materials, root blockage during transportation and storage, and adhesion of the mineral raw materials to the equipment. The mineral raw material in the method of the present invention is preferably at least one selected from the group consisting of coal, iron, coke and iron oxide. [Effects of the Invention]

[0015] According to the present invention, it is possible to provide a method for suppressing equipment damage caused by mineral raw materials by suppressing natural oxidation and heat generation during transportation and storage of mineral raw materials having a specific moisture content and particle size, and improving the handleability of the mineral raw materials during transportation and storage. The method of the present invention can contribute to the safety of mineral raw materials during transportation and storage. DETAILED DESCRIPTION OF THE INVENTION

[0016] The present invention is a method for suppressing equipment failure caused by mineral raw materials, which includes a contacting step of contacting a mineral raw material having a moisture content of 1 to 30% by weight and containing 70% or more by weight of particles with a particle diameter of 8 mm or less with a polymer dispersant to obtain a dispersant-containing mineral raw material, wherein in the contacting step, the mineral raw material is contacted with the polymer dispersant so that the particle diameter of 95% or more by weight of the polymer dispersant after the contacting step is 110% or more but less than 500% of the average particle diameter of the polymer dispersant before the contacting step, and the moisture content of 95% or more by weight of the dispersant-containing mineral raw material after the contacting step is 1 to 12% by weight. In this specification, the dispersant-containing mineral raw material is a mineral raw material containing a polymer dispersant, and can also be referred to as a mixture of a polymer dispersant and a mineral raw material.

[0017] As mentioned above, mineral raw materials generate heat through oxidation, and therefore, if the mineral raw material has a low moisture content, it is more likely to spontaneously combust. On the other hand, if the mineral raw material has a high moisture content, it will adhere to equipment, making it difficult to handle during storage and transportation, and reducing equipment efficiency and safety. Therefore, there is a trade-off between suppressing heat generation in mineral raw materials and their ease of handling during storage and transportation. For example, a known technique for suppressing heat generation in mineral raw materials involves spraying surfactants or highly water-absorbent polymers and water to coat the surface of piled and stored mineral raw materials (Patent Document 5). However, techniques for suppressing heat generation by coating the surface of mineral raw materials have the drawback that the surface layer of the piled mineral raw materials may crumble, or the surface coating may collapse during transportation, resulting in the loss of the heat suppression effect. Another known technique for suppressing or delaying heat generation in mineral raw materials is spraying surfactants and water on the mineral raw materials. However, as the moisture content of mineral raw materials increases, as described above, the mineral raw materials adhere to the hoppers of storage facilities and the belt conveyors of transport facilities, causing blockages and equipment failures due to adhesion, leading to problems such as reduced equipment efficiency and reduced safety due to the deterioration of the handleability of the mineral raw materials. Therefore, conventionally, techniques have been implemented to suppress heat generation due to oxidation of the mineral raw materials when storing the mineral raw materials, and techniques have been implemented to prevent and suppress adhesion of the mineral raw materials when transporting the mineral raw materials. The present invention is a method for suppressing equipment damage caused by heat generation due to oxidation of mineral raw materials and adhesion of mineral raw materials (spontaneous combustion of mineral raw materials, clogging during transportation and storage, adhesion of mineral raw materials to equipment, etc.), and solves problems that have previously been considered separately with a single method (i.e., the method of the present invention).

[0018] The inventors have discovered that by contacting a mineral raw material having a specific moisture content and a specific particle size with a polymeric dispersant under specific conditions, it is possible to suppress heat generation due to oxidation of the mineral raw material, and further to suppress problems caused by adhesion of the mineral raw material (for example, root clogging during transportation and storage, adhesion of the mineral raw material to equipment), thereby improving the safety and ease of handling of the mineral raw material, and have completed the present invention.

[0019] The type of mineral raw material that can be used in the method of the present invention is not particularly limited as long as it generates heat through oxidation, and examples include coal, iron, coke, iron oxide, limestone, iron ore, sintered ore, steel mill dust, and sludge. These may be used alone or as a mixture of two or more types. In this specification, the term "mineral raw material" includes the mineral raw material itself, as well as mineral raw materials that have been pretreated, such as crushed, particle size adjusted, agglomerated, agglomerated, and granulated, depending on the intended use. For example, when the "mineral raw material" is "coal," it includes coal itself and coal that has been pretreated, such as crushed, particle size adjusted, agglomerated, agglomerated, and granulated, depending on the intended use. The mineral raw material is preferably at least one selected from the group consisting of coal, iron, coke, and iron oxide.

[0020] The mineral raw material in the present invention has a moisture content of 1 to 30% by weight. Generally, mineral raw materials with a moisture content of more than 30% by weight are slurried and are used much less frequently. Furthermore, slurried mineral raw materials have fluidity, making them less likely to adhere to equipment, generate heat due to oxidation, or spontaneously combust. In other words, mineral raw materials with a moisture content of more than 30% by weight are less likely to cause equipment damage, and therefore the moisture content of the mineral raw materials in the present invention is 30% by weight or less. Furthermore, if the moisture content of the mineral raw material is less than 1% by weight, it is difficult to reduce the moisture content to less than 1% by weight even after a long period of treatment in the drying process.

[0021] (Method for measuring moisture content (moisture content) of mineral raw materials) The moisture content of the mineral raw material can be measured, for example, by a heat drying method, specifically, by an infrared moisture meter (FD-230, manufactured by Kett Electric Laboratory Co., Ltd.) The moisture content (Wi) in the present invention is calculated from the free moisture content (Wf), which indicates the content of water that evaporates and is removed under general drying conditions, and the equilibrium moisture content (We), at which drying does not proceed any further, and is a value represented by the following formula (I): (Equation I) Wi = Wf + We The method for measuring the moisture content is not particularly limited, and any method commonly used for measuring moisture content can be used. For example, the moisture content of coal and coke can be measured in accordance with JIS M8812. The moisture content of iron ore, limestone, and sintered ore can be measured in accordance with JIS M8705. The moisture content of the mineral raw material can be calculated from the moisture content obtained by measurement.

[0022] The polymer dispersant used in the method of the present invention is not particularly limited as long as it disperses the water contained in the mineral raw material and the particle size of 95% or more by weight of the polymer dispersant after contact with the mineral raw material is 110% or more but less than 500% of the average particle size of the polymer dispersant before contact. If the particle size of 95% or more by weight of the polymer dispersant after contact with the mineral raw materials (i.e., after the contact step in the present invention) is 110% or less of the average particle size of the polymer dispersant before contact with the mineral raw materials (i.e., before the contact step in the present invention), the water retention capacity of the polymer dispersant that has come into contact with and is dispersed in the mineral raw materials will be low, and there is a possibility that heat generation due to oxidation of the mineral raw materials will not be sufficiently suppressed. Furthermore, if the particle size of 95% or more by weight of the polymeric dispersant after contact with the mineral raw materials (i.e., after the contact step in the present invention) is 500% or more of the average particle size of the polymeric dispersant before contact with the mineral raw materials (i.e., before the contact step in the present invention), the water retention capacity of the polymeric dispersant that comes into contact with and is dispersed in the mineral raw materials will increase, making it more susceptible to deformation and potentially making it unable to stably disperse water in a particulate form due to flow. Furthermore, even if the moisture content of the mineral raw materials is reduced to suppress adhesion, if the water retention capacity of the polymeric dispersant in contact with the mineral raw materials increases and the polymeric dispersant becomes sticky, this may cause clogging in equipment such as hoppers for the mineral raw materials or adhesion to belt conveyors, potentially resulting in deterioration of handleability, safety, and equipment efficiency. The polymer dispersant used in the method of the present invention disperses the water contained in the mineral raw material, and after contact with the mineral raw material (after the contact step), the particle size of 95% or more by weight of the polymer dispersant is preferably 115% or more but less than 500%, and more preferably 120% or more but less than 500%, of the average particle size of the polymer dispersant before contact (before the contact step). The polymer dispersant used in the method of the present invention disperses the water contained in the mineral raw material, and after contact with the mineral raw material (after the contact step), the particle size of 95% or more by weight of the polymer dispersant is preferably 110% or more but less than 450%, more preferably 110% or more but less than 420%, and even more preferably 110% or more but less than 400%, of the average particle size of the polymer dispersant before contact (before the contact step). In the present invention, the preferred lower limit and the preferred upper limit of the average particle size of the polymer dispersant after the contact step can be combined as appropriate.

[0023] Examples of polymer dispersants include polyacrylic acid (salts), polyacrylic acid esters, polyacrylamides, polymethacrylic acid (salts), polymethacrylic acid esters, polyalkyleneimines, polyoxyalkylenes, polymaleic acids, polymers of these monomers, and copolymers of these monomers with other monomers.

[0024] Monomers for polyacrylic acid (salts) include acrylic acid, sodium acrylate, potassium acrylate, ammonium acrylate, etc.; monomers for polyacrylic esters include methyl acrylate, ethyl acrylate, n-propyl acrylate, n-butyl acrylate, isobutyl acrylate, hydroxyethyl acrylate, 2-ethylhexyl acrylate, etc.; monomers for polymethacrylic acid (salts) include methacrylic acid and sodium methacrylate; monomers for polymethacrylic esters include methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, hydroxyethyl methacrylate, 2-ethylhexyl methacrylate, etc.; monomers for polyalkyleneimines include ethyleneimine and methylethyleneimine; monomers for polyoxyalkylenes include ethylene oxide, etc.; and other monomers include vinylsulfonic acid, styrenesulfonic acid, acrylamide, methacrylamide, N-ethyl(meth)acrylamide, vinylpyridine, etc.

[0025] The polymer dispersant is preferably at least one selected from the group consisting of polyacrylic acid, sodium polyacrylate, calcium polyacrylate, and ammonium polyacrylate, and more preferably sodium polyacrylate and / or ammonium polyacrylate. The polymer dispersant may be used alone or in combination of two or more kinds.

[0026] The amount of polymer dispersant added is not particularly limited, but is preferably 0.02 to 1 part by weight per 100 parts by weight of mineral raw material. If the amount of polymer dispersant is less than 0.02 parts by weight per 100 parts by weight of mineral raw material, the moisture content of the mineral raw material will not be 10% by weight or less, which may cause the mineral raw material with a high moisture content to adhere to the equipment and make it impossible to prevent equipment damage. If the amount of polymer dispersant is more than 1 part by weight per 100 parts by weight of mineral raw material, an excess of polymer dispersant will be present, which may increase impurities in the mineral raw material and is undesirable from a cost-effectiveness perspective. The lower limit of the amount of polymer dispersant to be added is preferably 0.02 parts by weight, more preferably 0.025 parts by weight, per 100 parts by weight of the mineral raw material. The upper limit of the amount of polymer dispersant added is preferably 1 part by weight, more preferably 0.8 parts by weight, and even more preferably 0.06 parts by weight, per 100 parts by weight of the mineral raw material. In the present invention, the above-mentioned suitable lower and upper limits of the amount of polymer dispersant can be combined as appropriate. The amount of polymer dispersant to be added may be determined according to the moisture content of the mineral raw material. Since the moisture content of the mineral raw material changes depending on the number of days since precipitation or watering and the humidity of the storage environment, it is preferable to determine the amount of polymer dispersant to be added according to the measured moisture content of the mineral raw material.

[0027] The method of the present invention includes a contacting step of contacting a mineral raw material having a moisture content of 1 to 30% by weight and containing 70% or more by weight of particles having a particle diameter of 8 mm or less with the above-mentioned polymer dispersant to obtain a dispersant-containing mineral raw material, in which the mineral raw material is contacted with the polymer dispersant so that the moisture content of the dispersant-containing mineral raw material (mineral raw material containing a polymer dispersant) after the contacting step is 1 to 12% by weight and is 95% or more by weight. By making the water content of the dispersant-containing mineral raw material after the contact step 1 to 12% by weight, natural oxidation and heat generation during transportation and storage of the mineral raw material can be suppressed, and the handleability of the mineral raw material during transportation and storage can be improved. In order to further suppress natural oxidation and heat generation during transportation and storage of the mineral raw material, the water content of the dispersant-containing mineral raw material after the contact step is preferably 3% or more, and more preferably 5% or more. Furthermore, from the viewpoint of further improving the handleability of the mineral raw material during transportation and storage, the moisture content of the dispersant-containing mineral raw material after the contact step is preferably 11% or less, and more preferably 10% or less. In the present invention, the preferred lower limit and the preferred upper limit of the water content of the dispersant-containing mineral raw material after the contact step can be combined as appropriate.

[0028] The polymer dispersant used in the method of the present invention preferably has an average particle size of 5 to 1400 μm. By contacting a mineral raw material containing 70% or more particles with a particle size of 8 mm or less with a polymer dispersant having an average particle size of 5 to 1400 μm, the moisture content of the mineral raw material can be effectively reduced, and sufficient effects can be obtained in suppressing natural oxidation and heat generation. If the average particle size of the polymer dispersant is smaller than 5 μm, the dispersibility of the water contained in the mineral raw material will be improved, but in terms of suppressing natural oxidation and heat generation of the mineral raw material, the specific surface area of the polymer dispersant relative to the water content of the mineral raw material will be large, and moisture retention may be insufficient due to evaporation from the polymer dispersant surface, which may result in the expected effect of suppressing natural oxidation and heat generation not being fully achieved. Furthermore, if the average particle size of the polymer dispersant is larger than 1400 μm, the polymer dispersant will have a large water absorption capacity, which will increase its water retention capacity, but the increased water absorption of the polymer dispersant will result in poor dispersibility of the water contained in the mineral raw materials, which may result in the desired uniform natural oxidation and heat generation suppression effect not being fully achieved. The average particle size of the polymer dispersant is a volume average particle size determined by a sieving method, and can be measured, for example, using a measurement method in accordance with JIS 8815. The polymer dispersant used in the method of the present invention preferably has an average particle size of 150 μm or more, and more preferably has an average particle size of 900 μm or less. In the present invention, the preferred lower and upper limits of the average particle size of the polymer dispersant can be appropriately combined.

[0029] In the method of the present invention, the equipment damage caused by the mineral raw materials is preferably at least one selected from the group consisting of spontaneous combustion of the mineral raw materials, root blockage during transportation and storage, and adhesion of the mineral raw materials to the equipment. The term "equipment" as used herein refers to, for example, equipment within a transfer line that transports mineral raw materials along a predetermined line from a mining and ore-dressing site, through a mineral raw material storage location such as a raw material yard, to equipment that uses the mineral raw materials, and refers to ship holds, trucks, freight car beds, raw material yards, piping, belt conveyors, belt conveyor transfer points, conveyor chains, chutes, hoppers, silos, blending tanks, crushers, coal humidity control equipment, coal loading cars, etc. Note that this also includes chutes, hoppers, silos, and other equipment that has a temporary storage function.

[0030] In the method of the present invention, the contacting step of contacting a mineral raw material having a moisture content of 1 to 30% by weight and containing at least 70% by weight of particles with a particle diameter of 8 mm or less with a polymeric dispersant to obtain a dispersant-containing mineral raw material may be performed either in the facility of the present invention described above or on a transfer line connecting one facility to another. The contacting step is not particularly limited, but it is preferable to contact the polymeric dispersant with the mineral raw material at a mineral raw material storage location or on a transfer line from the mineral raw material storage location. This allows the mineral raw material and the polymeric dispersant to be mixed each time the mineral raw material changes positions on a transfer line such as a belt conveyor, thereby dispersing the polymeric dispersant in the mineral raw material. When the mineral raw material is brought into contact with the polymer dispersant in the storage location or container of the mineral raw material, it is preferable to mix them by appropriate stirring.

[0031] The method for contacting the polymer dispersant with the mineral raw material is not particularly limited, and examples thereof include spraying, compressed air feeding, and using a screw feeder. Furthermore, the method for mixing the polymer dispersant and the mineral raw material is not particularly limited, and examples thereof include a method of mixing using heavy machinery, a method of mixing using the impact of a transfer point on a belt conveyor, and a method of mixing using a mixing device such as a mixer.

[0032] The method of the present invention may further include a moisture adjustment step, either simultaneously with the contact step or after the contact step, in which water is added to the dispersant-containing mineral raw material (mineral raw material containing a polymer dispersant) to adjust the moisture content so that the particle size of 95% or more by weight of the polymer dispersant after the contact step is 110% or more but less than 500% of the average particle size of the polymer dispersant before the contact step, and the moisture content of 95% or more by weight of the dispersant-containing mineral raw material after the contact step is 1 to 12% by weight. In addition, in the moisture adjustment step, it is preferable to add water to the dispersant-containing mineral raw material so that the particle size of 95% by weight or more of the polymer dispersant after the contact step is 115% or more, and it is more preferable to add water so that it is 200% or more. In addition, in the moisture adjustment step, it is preferable to add water to the dispersant-containing mineral raw material so that the moisture content of 95% or more by weight of the dispersant-containing mineral raw material after the contact step is 3% or more, and it is more preferable to add water so that the moisture content is 5% or more. In addition, the moisture content can be adjusted in the moisture adjustment step to fall within a range that is an appropriate combination of the above-mentioned preferable lower limit and preferable upper limit. In the equipment failure prevention method of the present invention, the moisture adjustment step may be carried out one or more times, and is preferably carried out in equipment such as a ship's hold, a truck, a freight car bed, a raw material yard, piping, a belt conveyor, a belt conveyor transfer section, a conveyor chain, a chute, a hopper, a silo, a blending tank, a pulverizer, a moisture-adjusting coal equipment, or a coal loading car.

[0033] According to the present invention, a dispersant-containing mineral raw material in which water is dispersed can be obtained. The present invention also provides a method for producing a dispersant-containing mineral raw material comprising a mineral raw material and a polymeric dispersant, the method comprising a contacting step of contacting a mineral raw material having a water content of 1 to 30% by weight and containing at least 70% by weight of particles with a particle size of 8 mm or less with the polymeric dispersant, wherein the mineral raw material is contacted with the polymeric dispersant in the contacting step such that the particle size of at least 95% by weight of the polymeric dispersant after the contacting step is at least 110% but less than 500% of the average particle size of the polymeric dispersant before the contacting step, and the water content of at least 95% by weight of the dispersant-containing mineral raw material after the contacting step is 1 to 12% by weight. As mentioned above, mineral raw materials have a high possibility of spontaneous combustion if their moisture content is low, while if their moisture content is high, they tend to adhere to equipment, making them difficult to handle during storage and transportation, and reducing equipment efficiency and safety. According to the production method of the present invention, the moisture held in the mineral raw materials is dispersed by the polymer dispersant, and it is possible to obtain mineral raw materials in a state where the moisture content of the mineral raw materials themselves is 1 to 12 wt % and the polymer dispersant that holds the moisture is dispersed around the mineral raw materials, thereby making it possible to obtain dispersant-containing mineral raw materials in which heat generation due to oxidation of the mineral raw materials and deterioration in handleability due to adhesion of the mineral raw materials are suppressed.

[0034] The aspects of the polymer dispersant, mineral raw material, polymer dispersant after the contact step, and dispersant-containing mineral raw material after the contact step, as well as their preferred aspects, in the method for producing dispersant-containing mineral raw material of the present invention, are the same as the aspects of the polymer dispersant, mineral raw material, polymer dispersant after the contact step, and dispersant-containing mineral raw material after the contact step, as well as their preferred aspects, in the method for suppressing equipment failure of the present invention. In the method for producing a dispersant-containing mineral raw material of the present invention, the method and position for contacting the polymer dispersant with the mineral raw material are the same as those in the method for suppressing equipment failure of the present invention. [Example]

[0035] The present invention will be explained in more detail below by showing examples, but the present invention is not limited to these examples.

[0036] <Test Example 1: Effectiveness Verification Test of Polymer Dispersant Average Particle Size> For a polymer dispersant (purchased from Katayama Nalco Corporation, Nalco_9922), the deformation rate was measured when the particle size when moistened was the ratio shown in Table 1 below, based on the average particle size when dry. The average particle size ratio (%) of the polymer dispersant was calculated using the average particle size (B) when the moisture had evaporated after drying at 105°C for 2 hours or more, and the average particle size (W) that increased upon contact with the mineral raw material containing moisture, according to the following formula II. (Equation II) Average particle size ratio (%) = W × 100 / B The deformation ratio was measured in accordance with JIS K7181. 20 cc of the polymer dispersant was filled in a container as a preliminary load, and initially, a 1 / 10 load was applied to eliminate voids between particles. After the measurement conditions were adjusted, a 1 kg / cm 2 A compression test was carried out at a pressure of 1000 kJ / cm2, and the deformation ratio (strain, (L0-L) / L0) was measured, where L0 is the height of the dispersant particles in the container after compression, and L is the height of the dispersant after deformation. The deformation ratio was converted to a percentage and used as an index of the deformation strength of the particles. At the same time, the presence or absence of adhesion of the dispersant particles to the load rod after the test was checked, and the presence or absence of surface stickiness was evaluated. The results are shown in Table 1.

[0037] (Nalco_9922) Ingredients: Polyacrylic acid polymer Sold by: Ecolab, Inc. Maximum water absorption rate: 280% Average particle size: 99% or more are 1 mm or less

[0038] [Table 1]

[0039] From the results in Table 1, it was confirmed that when the ratio of the average particle size of the polymer dispersant containing water to the average particle size of the polymer dispersant in a dry state increases by 500% or more, the deformation rate also increases, the polymer dispersant softens, becomes sticky, and gelation progresses. As a result, the fluidity of the polymer dispersant increases, it becomes prone to uneven flow, it is no longer able to stably retain moisture, and it is no longer able to exert its full effect as a dispersant.

[0040] <Example 1: Temperature rise suppression effect test using subbituminous coal powder> 200 g of subbituminous coal from a certain steelworks, having the particle size distribution shown in Table 2 below, was dried with hot air for 2 hours, after which the initial moisture content was measured and the coal was transferred to a 350 cc container, and a polymer dispersant (Nalco_9922) and water, or water alone, were added to achieve the moisture content shown in Table 3 below, thereby obtaining subbituminous coals A to F according to Examples 1-1 and 1-2 and Comparative Examples 1-1 to 1-4. Next, the obtained subbituminous coals A to F were heated under the conditions shown below, and the time (h) for the subbituminous coal to reach 150°C and 200°C by heating was measured. (Heating conditions) Three thermocouples were placed inside the container to measure the internal temperature of the sample: two at equal intervals from the side, bottom, and surface of the sample, spaced 1–1.5 cm apart. Another thermocouple was placed 0.5 cm inside the container, at the center of the sample's height, to measure the temperature of the inner surface. The container was then heated from the outside using an infrared heater tailored to the size of the container. The temperature during heating was controlled by measuring the internal and inner surface temperatures using thermocouples placed at the center and inner surface of the sample. The heater was turned on when the temperature difference between the inner surface and the inner center reached 10°C, based on the average temperature rise of the two thermocouples in the inner center, and turned off when the temperature difference reached 20°C. The heating temperature was adjusted so that the inner surface temperature was 10–20°C higher than the inner center temperature. The time (h) required for the subbituminous coal to reach 150°C and 200°C is shown in Table 3. The initial moisture content of the subbituminous coal after drying with hot air for 2 hours was 3%.

[0041] [Table 2]

[0042] [Table 3]

[0043] From the results in Table 3 above, it can be seen that for subbituminous coals A and B, which took 30 hours or more to reach 150°C, the average particle size ratio of the polymer dispersant used was 118% and 129%. From the results for subbituminous coal C, which took 5.8 hours to reach 150°C, it was confirmed that when the ratio of the average particle size of the polymer dispersant used after retaining moisture to the average particle size of the polymer dispersant when dry (the average particle size of the polymer dispersant before contact with the subbituminous coal) is less than 110%, the time to reach 150°C is short at 5.8 hours, and a sufficient heat generation suppression effect cannot be obtained (Comparative Example 1-1). Furthermore, the results of Comparative Examples 1-2 and 1-3 show that even when the moisture content of the subbituminous coal was 7% and 11%, respectively, and the subbituminous coals D and E, to which no polymer dispersant was added, took a short time to reach 150°C, and were unable to achieve a sufficient heat generation suppression effect.

[0044] <Example 2: Temperature rise suppression effect test using dust containing iron oxide> 200 g of dust components of converter gas (Fe; 50%, iron oxide (FeO, Fe2O3); 40%, other components (Ca, Si, Mn, Mg, etc.; 10%)) having the particle size distribution shown in Table 4 below was dried with hot air for 2 hours, and then the initial moisture content was measured. The sample was then transferred to a 350 cc container, and a polymer dispersant (Nalco_9922) and water, or water only, were added to achieve the moisture content shown in Table 5 below, thereby obtaining dusts G to K according to Examples 2-1 and 2-2 and Comparative Examples 2-1 to 2-3. A temperature rise suppression effect test was conducted under the same conditions as in Example 1, except that dusts G to K were used instead of subbituminous coals A to F, and the time (h) for the dust to reach 150°C and 200°C by heating was measured. The results are shown in Table 5 below. The initial moisture content of the dust after drying with hot air for 2 hours was 2.5%.

[0045] [Table 4]

[0046] [Table 5]

[0047] From the results in Table 5 above, for dusts G and H, which took more than 12 hours to reach 150°C, the ratio of the average particle size of the polymer dispersant used after retaining moisture was 116% and 124% of the average particle size of the polymer dispersant when dry (the average particle size of the polymer dispersant before contact with the dust). On the other hand, when no polymer dispersant was used, the time required to reach 150°C was within 3 hours even when the dust had a moisture content of 6% or 10% and was in a wet state (Comparative Examples 2-1 to 2-3).

[0048] From the results of Test Example 1 above, it was confirmed that when the ratio of the average particle size of the polymer dispersant after contact with the mineral raw material becomes 500% or more of the average particle size of the polymer dispersant before contact, adhesion occurs due to deformation of the polymer dispersant. Furthermore, from the results of Examples 1 and 2, it was confirmed that heat generation of the mineral raw material can be effectively suppressed by contacting a mineral raw material having a moisture content of 1 to 30% by weight and containing 70% by weight or more of particles with a particle diameter of 8 mm or less with a polymer dispersant, and by ensuring that the average particle diameter of the polymer dispersant after contact is 110% or more of the average particle diameter of the polymer dispersant before contact. That is, from the results of Test Example 1 and Examples 1 and 2, it was confirmed that the contact step involves contacting a mineral raw material having a moisture content of 1 to 30% by weight and containing at least 70% by weight of particles with a particle diameter of 8 mm or less with a polymer dispersant to obtain a dispersant-containing mineral raw material, and that by contacting the mineral raw material with the polymer dispersant in the contact step so that the particle diameter of at least 95% by weight of the polymer dispersant after the contact step is at least 110% but less than 500% of the average particle diameter of the polymer dispersant before the contact step, and that the moisture content of at least 95% by weight of the dispersant-containing mineral raw material after the contact step is 1 to 12% by weight, heat generation and adhesion of the mineral raw material can be suppressed.

Claims

1. A method for suppressing equipment failure caused by mineral raw materials, comprising: a contacting step of contacting a mineral raw material having a moisture content of 1 to 30% by weight and containing 70% by weight or more of particles having a particle diameter of 8 mm or less with a polymer dispersant to obtain a dispersant-containing mineral raw material; In the contacting step, the mineral raw material is contacted with the polymer dispersant so that the particle size of 95% by weight or more of the polymer dispersant after the contacting step is 110% or more but less than 500% of the average particle size of the polymer dispersant before the contacting step, and the moisture content of 95% by weight or more of the dispersant-containing mineral raw material after the contacting step is 1 to 12% by weight; The method for suppressing equipment failure, characterized in that the equipment failure is equipment failure caused by natural oxidation, heat generation or spontaneous combustion during storage of mineral raw materials.

2. 2. The method for suppressing equipment failure according to claim 1, wherein the average particle size of the polymer dispersant before the contact step is 5 to 1,400 μm.

3. A method for suppressing equipment failures as described in claim 1 or 2, in which the mineral raw material is contacted with the polymer dispersant so that the moisture content of the dispersant-containing mineral raw material, which is 95% by weight or more after the contact step, is 5 to 12% by weight.

4. 4. The method for suppressing equipment failure according to claim 1, 2 or 3, wherein the mineral raw material is at least one selected from the group consisting of coal, iron, coke and iron oxide.

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