Method for producing humic acid-containing powder, humic acid-containing water, method for improving soil, and method for promoting plant growth.

Abstract

The humic-acid-containing powder has a degree of compaction of 5-20. The degree of compaction is a value calculated by the formula {(rhoP - rhoA) / rhoP} × 100, where rhoA is the aerated bulk density of the powder and rhoP is the packed bulk density of the powder. Humic-acid-containing water obtained by dissolving or dispersing the humic-acid-containing powder in water is preferably used for soil improvement and plant growth promotion.

Description

Technical Field

[0001] The present invention relates to a method for producing humic acid-containing powder and humic acid-containing water, a method for improving soil, and a method for promoting plant growth. More specifically, it relates to a humic acid-containing powder having predetermined characteristics, a method for producing humic acid-containing water using the humic acid-containing powder, a method for improving soil using the humic acid-containing water, and a method for promoting plant growth using the humic acid-containing water.

Background Art

[0002] Humic acid is said to have effects such as promoting plant growth. Therefore, it has been proposed to use humic acid as a fertilizer. Humic acid exists in soil and surface water. Specifically, humic acid is contained in lignite or peat, or exists as a metabolite of bacterial flora. There is also natural humic acid derived from animals and plants. Industrially, humic acid, which is an oxidative decomposition product of young coals such as lignite, or an alkali metal salt or alkaline earth metal salt of its oxidative decomposition product is known. Patent Documents 1 and 2 describe a method for producing a humic acid extract and a specific humic acid extract.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] Patent Documents 1 and 2 describe a humic acid extract, that is, liquid humic acid.

[0005] On the other hand, considering ease of transportation and storage, it is also possible to manufacture humic acid in powder form in advance, dissolve it in water to create an aqueous solution, and use that solution as a fertilizer or soil conditioner. In fact, powdered humic acid is available on the market.

[0006] However, according to the inventors' findings, conventional powdered humic acid on the market had room for improvement in terms of industrial handling. For example, conventional powdered humic acid had room for improvement in terms of its fluidity as a powder. Poor fluidity of powdered humic acid can lead to concerns that the humic acid may not be discharged smoothly from silos or hoppers, or that the flow path may become blocked.

[0007] This invention has been made in view of these circumstances. One of the objects of this invention is to provide a humic acid-containing powder that has good fluidity as a powder. [Means for solving the problem]

[0008] The present inventors have completed the invention described below and solved the above-mentioned problems.

[0009] 1. A humic acid-containing powder with a compression degree of 5-20. 2. The humic acid-containing powder described in 1. Looseness density is 0.2-0.5 g / cm³ 3 It is a humic acid-containing powder. 3. A humic acid-containing powder as described in 1. or 2., Median diameter D 50 A humic acid-containing powder with a particle size of 10-200 μm. 4. A humic acid-containing powder as described in any one of 1. to 3., A humic acid-containing powder with a melanic index of 2-5. 5. A humic acid-containing powder as described in any one of 1. to 4., A humic acid-containing powder with a moisture content of 15% by mass or less. 6. A method for producing humic acid-containing water, comprising dissolving or dispersing a humic acid-containing powder described in any one of items 1 to 5 in water. 7. A soil improvement method comprising spraying humic acid-containing water, produced by the manufacturing method described in 6., onto the soil. 8. A method for promoting plant growth, comprising supplying plants with humic acid-containing water produced by the manufacturing method described in 6. 9. Humic acid-containing material with a compression degree of 5-20. [Effects of the Invention]

[0010] According to the present invention, a humic acid-containing powder with good fluidity as a powder is provided. [Brief explanation of the drawing]

[0011] [Figure 1] This diagram schematically illustrates the structure and operating principle of a disc dryer. [Figure 2] This figure schematically shows the shape of the stainless steel container used in the performance evaluation of the example. [Figure 3] This figure illustrates a method for evaluating the stability of a bagged humic acid-containing powder in an example. [Modes for carrying out the invention]

[0012] Embodiments of the present invention will be described in detail below with reference to the drawings. In the drawings, similar components are denoted by the same reference numerals, and explanations are omitted where appropriate. To avoid complexity, if there are multiple identical components within the same drawing, a reference numeral may be assigned to only one of them, and not to all of them. All drawings are for illustrative purposes only. The shapes and dimensional ratios of the components shown in the drawings do not necessarily correspond to actual items.

[0013] In this specification, the notation "X to Y" in the description of a numerical range represents X or more and Y or less, unless otherwise specified. For example, "1 to 5 mass%" means "1 mass% or more and 5 mass% or less".

[0014] <Humic acid-containing powder> The degree of compression of the humic acid-containing powder of this embodiment is 5 to 20, preferably 6.5 to 18, more preferably 8 to 17, and particularly preferably 10 to 16. The degree of compression is defined as the bulk density of the loose powder being ρ A and the bulk density of the compacted powder being ρ P [[ID=十三]]When this is the case, the value calculated by the formula { (ρ P - ρ A ) / ρ P} × 100.

[0015] The humic acid-containing powder of this embodiment is considered to have good fluidity as a powder because its degree of compression is 5 to 20. The reason for this is not necessarily clear, but it can be explained as follows. The fact that the degree of compression is 20 or less means that the values of the bulk density of the loose powder ρ A and the bulk density of the compacted powder ρ P are relatively close. That is, it can be said that a humic acid-containing powder with a degree of compression of 20 or less has good fluidity such that the gaps between the particles constituting the powder are reduced without applying force. On the other hand, considering industrial productivity and manufacturing costs, etc., it is unrealistic to produce a humic acid-containing powder with a degree of compression close to zero. Therefore, in this embodiment, the lower limit value of the degree of compression is set to 5.

[0016] Incidentally, as a secondary effect of the degree of compression being 5 to 20, it is also possible to expect the effect that when stacking bags filled with the humic acid-containing powder, they can be stacked stably. Such an effect leads to the stable storage of the humic acid-containing powder and the prevention of cargo collapse when transporting the humic acid-containing powder by truck, train, ship, etc. Because the compression degree of the humic acid-containing powder is 20 or less, even if vibration or other external forces are applied to the bagged humic acid-containing powder, the volume change of the powder is kept to a minimum. Therefore, the bagged humic acid-containing powder of this embodiment is easy to store or transport stably.

[0017] The humic acid-containing powder of this embodiment can be manufactured using appropriate raw materials and following an appropriate manufacturing process. A suitable manufacturing process is preferably one using a disc dryer. Specifically, a humic acid-containing powder with a compression degree of 5 to 20 can be produced by evaporating water from a humic acid-containing liquid (such as a humic acid extract) using a disc dryer with appropriately set disc rotation speed and drying temperature. To the best of the inventors' knowledge, it is difficult to produce humic acid-containing powder with a compression degree of 5 to 20 using any powdering method other than powdering with a disc dryer. However, this does not mean that the method for producing humic acid-containing powder in this embodiment is limited. The raw materials and manufacturing process will be described in detail later.

[0018] The description of the humic acid-containing powder of this embodiment will continue.

[0019] (Compression, loose bulk density, and stiff bulk density) The degree of compression of the humic acid-containing powder in this embodiment may be 5 to 20 as described above. Preferably, the degree of compression is 6.5 to 18, more preferably 8 to 17, and particularly preferably 10 to 16. The loose bulk density of the humic acid-containing powder in this embodiment is preferably 0.2 to 0.5 g / cm³. 3 , more preferably 0.3 to 0.4 g / cm³ 3 That is the case. The bulk density of the humic acid-containing powder in this embodiment is preferably 0.25 to 0.6 g / cm³. 3 , more preferably 0.35~0.5 g / cm³ 3 That is the case. By appropriately adjusting not only the degree of compression but also the loose bulk density and stiff bulk density, it is sometimes possible to further enhance the fluidity of the powder or improve its handling properties other than fluidity.

[0020] (particle size distribution) As described above, the median diameter D of the humic acid-containing powder of this embodiment 50 The particle size is preferably 10 to 200 μm. 50 The particle size is preferably 30 to 150 μm, and more preferably 50 to 120 μm. Median diameter D 50 The fact that the particle size is a relatively large value of 10 μm or more means that the alteration and deterioration of the humic acid-containing powder in this embodiment is suppressed. 50 Large humic acid-containing powders are D 50 Compared to humic acid-containing powders with a small surface area, the surface area per unit volume is smaller, so it is thought that alteration and deterioration due to oxygen and moisture in the atmosphere are suppressed. Also, D 50 Because the humic acid-containing powder has a relatively large surface area, when dissolving or dispersing the humic acid-containing powder in water, the humic acid-containing powder repels water less, making it easier to prepare aqueous solutions or dispersions of the humic acid-containing powder. Meanwhile, D 50 Having particles smaller than 200 μm can sometimes shorten the time required to completely dissolve humic acid-containing powder in water. A shorter dissolution time leads to time savings and increased efficiency when dissolving humic acid-containing powder in water to create humic acid-containing water, which can then be applied to soil or given to plants.

[0021] The cumulative 10% diameter of the humic acid-containing powder in this embodiment is D 10 In that case, D 10 The particle size is preferably 10 μm or more, more preferably 10 to 50 μm, and even more preferably 10 to 40 μm. 10When the particles are 10 μm or larger, or in other words, when the amount of fine particles smaller than 10 μm in the humic acid-containing powder is less than 10%, the scattering of the humic acid-containing powder due to static electricity is suppressed, and the handling of the humic acid-containing powder tends to improve (fine particles tend to scatter easily due to static electricity).

[0022] From a similar perspective, (D 50 -D 10 ) / D 50 The value of is preferably 0.1 to 1, more preferably 0.2 to 0.9, and even more preferably 0.3 to 0.8. (D 50 -D 10 ) / D 50 The fact that is 1 or less means that in the particle size distribution of the humic acid-containing powder, D 50 This means that the particle size distribution on the smaller particle size side is sharper. In other words, (D 50 -D 10 ) / D 50 A value of 1 or less means that the proportion of fine particles that are easily dispersed by static electricity in the humic acid-containing powder is small. Incidentally, (D 50 -D 10 ) / D 50 The preferred lower limit of 0.1 is set with industrial manufacturability in mind.

[0023] From another perspective, the cumulative 90% diameter of the humic acid-containing powder in this embodiment is D. 90 In that case, D 90 The particle size is preferably 80-300 μm, more preferably 100-250 μm, and even more preferably 130-230 μm. 90 When the particle size is 300 μm or less, in other words, when the amount of fine particles larger than 300 μm in the humic acid-containing powder is less than 10%, the amount of undissolved coarse particles is reduced, and the solubility of the humic acid-containing powder in water tends to be better. Also, (D 90 -D 50 ) / D 50 The value is preferably 0.7 to 1.6, more preferably 0.8 to 1.4. (D 90 -D 50 ) / D 50The fact that is 1.6 or less means that in the particle size distribution of the humic acid-containing powder, D 50 This means that the particle size distribution on the larger particle size side is sharper. In other words, (D 90 -D 50 ) / D 50 A value of 1.6 or less means that the proportion of coarse particles that tend to remain undissolved in the humic acid-containing powder is small. Incidentally, (D 90 -D 50 ) / D 50 The preferred lower limit of 0.7 is set with industrial manufacturability in mind.

[0024] D 10 , D 50 and D 90 The value of can be measured dry by laser diffraction and scattering. The value obtained by laser diffraction and scattering is D 10 , D 50 and D 90 The value of is usually a volume-based value. D as described in this specification 10 , D 50 and D 90 Unless otherwise specified, the values ​​are based on volume. Measurements can be performed using equipment manufactured by, for example, HORIBA Corporation.

[0025] (Melanic Index (MI)) The humic acid-containing powder of this embodiment preferably has an appropriate melanic index (MI). The MI is preferably 2 to 5, more preferably 2.0 to 5.0, even more preferably 2 to 3, and particularly preferably 2.0 to 3.0. An MI within this numerical range is considered to mean that the humic acid in the humic acid-containing powder has an appropriate amount of hydrophilic groups. The presence of an appropriate amount of hydrophilic groups is considered to further improve the water solubility or water dispersibility of the powder. The method for measuring MI is described later in the section "Method for producing crude humic acid," as steps (1) to (5). However, if the particle size of the humic acid-containing powder is sufficiently small, the grinding and sieving in step (1) may be unnecessary.

[0026] (Moisture percentage) The moisture content of the humic acid-containing powder in this embodiment is preferably 15% by mass or less, more preferably 1 to 15% by mass, even more preferably 3 to 12% by mass, and particularly preferably 5 to 10% by mass. By keeping the moisture content low, improvements in storage properties can be expected, such as suppression of clumping during storage and inhibition of humic acid deterioration. Furthermore, a low moisture content tends to prevent humic acid-containing powder from adhering to the container walls. In short, a low moisture content tends to further improve industrial handling properties such as fluidity. While a low moisture content is acceptable, it doesn't necessarily have to be close to zero, as there's a trade-off between the energy cost of removing moisture and the improvements in storage and handling mentioned above.

[0027] (Ingredients for humic acid-containing powder) For example, humic acid-containing powder can be manufactured using humic acid extract as a raw material. For example, humic acid extract can be produced by first oxidizing young coal such as lignite with nitric acid to obtain a crude humic acid product, and then extracting humic acid from that crude product. The following describes a method for producing crude humic acid and a method for extracting humic acid from crude humic acid.

[0028] • Method for producing crude humic acid As mentioned above, crude humic acid can be obtained by oxidizing young coal such as lignite with nitric acid. Young coal is defined as coal with a low carbon content, specifically coal with a carbon content of 83% by mass or less. Preferably, young coal with a carbon content of 78% by mass or less is used. Such young coal is still in the process of coalification and contains many aliphatic hydrocarbon structures, making it susceptible to oxidative decomposition by nitric acid. As young coal, one or more of the following can be used: peat, lignite, brown coal, subbituminous coal, etc.

[0029] For oxidation with nitric acid, it is preferable to mix 500 to 1000 kg of concentrated nitric acid (anhydrous equivalent) per 1000 kg of young coal. The mixing time can be, for example, 20 to 60 minutes. Oxidation with nitric acid is a vigorous chemical reaction accompanied by foaming. Since vigorous foaming can make it difficult to control the chemical reaction, an antifoaming agent may be used. As an antifoaming agent, considering that humic acid is used for soil improvement, it is preferable to use hydrophobic silica, which has a composition similar to that of soil. Examples of commercially available hydrophobic silica include Evonik's SIPERNAT series.

[0030] By adjusting the amount of nitric acid added, the melanic index (hereinafter abbreviated as MI) of the resulting crude humic acid can be made to 2.0 to 3.0. MI is an index used for classifying humic acid, and is the ratio of the absorbances at wavelengths of 450 nm and 520 nm of the absorption spectrum of the sodium hydroxide extract (A 450 / A 520 ) is defined as follows. (Reference: Kyoichi Kumada, "Chemistry of Soil Organic Matter, 2nd Edition," Academic Publishing Center (1981), Japanese Journal of Soil Science and Plant Nutrition, No. 71, No. 1, pp. 82-85 (2000)).

[0031] More specifically, MI can be calculated using the following procedure. (1) The sample is ground in a mortar and pestle, and then a 250 μm sieve is used to obtain the sieved-down product. (2) Take approximately 10 g of the sample that has passed through the 250 μm sieve and weigh it accurately in a weighing bottle of known mass. Leave this weighing bottle in a drying oven maintained at a temperature of 105 °C for approximately 12 hours, then return it to room temperature in a desiccator and weigh it accurately again. The amount of mass lost is considered to be water to determine the water content of the sample. (3) Place 0.10 g of the above 250 μm sieved material (dry mass equivalent) and 45 mL of 0.5 mol / L sodium hydroxide aqueous solution into a 50 mL centrifuge tube and shake at a speed of 250 rpm for about 1 hour at room temperature (20°C). (4) After shaking is complete, perform centrifugation at 3,000 x g for about 10 minutes. Filter the obtained supernatant through Advantec No. 5C filter paper to obtain the filtrate. Measure the absorbance of the filtrate at 450 nm and 520 nm using distilled water as a blank. If the absorbance at 450 nm is 1.0 or higher, add 0.1 mol / L sodium hydroxide aqueous solution to adjust the absorbance to between 0.8 and 1.0, and then measure the absorbance at 520 nm. (5) Calculate the ratio of (absorbance at 450 nm / absorbance at 520 nm) and define it as MI.

[0032] A MI of 2.0 or higher, as measured as described above, indicates that the humic acid in the crude humic acid product has sufficient hydrophilic groups, resulting in good water solubility. In other words, the extraction rate in water (specifically water with a pH of 7.0 or lower) improves. Furthermore, an MI of 3.0 or lower suppresses excessive oxidation reactions, leading to a reduction in nitric acid costs.

[0033] The MI (Minimum Indication) can be increased or decreased by adjusting the amount of nitric acid used in the production of crude humic acid. Generally, increasing the amount of nitric acid increases the MI. From the above perspective, it is preferable to increase the MI by increasing the amount of nitric acid, but considering the balance with cost, an MI of 3.0 or less is preferable. From the viewpoint of balancing improved extraction efficiency with cost, the MI is more preferably 2.2 to 3.0, and even more preferably 2.2 to 2.4. Incidentally, the MI of natural humic acid is generally 1.7 or less.

[0034] (Method for extracting humic acid from crude humic acid product) To the crude humic acid obtained as described above, or to crude humic acid obtained by other methods, water is added, and an alkali such as potassium hydroxide is added as appropriate to achieve a pH of, for example, 1 to 7, preferably 5 to 7, or 1 to 3. The resulting liquid is typically stirred at 40 to 90°C for 0.5 to 1 hour, and then cooled to below 40°C. A humic acid extract can be obtained by separating the unreacted residue from the cooled liquid using methods such as centrifugation or filter pressing.

[0035] Let me explain "humic acid" in the context of humic acid extract, just in case. Unless otherwise specified, "humic acid" in this specification includes humic acid itself and salts of humic acid. Examples of humic acid include naturally occurring humic acid found in peat and weathered coal, and artificially produced humic acid, such as that produced by nitrate oxidation of lignite. Other examples include humic acid salts obtained by neutralizing natural or artificial humic acid with alkaline substances such as sodium, potassium, ammonia, calcium, and magnesium. In this embodiment, humic acid obtained by nitrate oxidation of lignite is particularly preferred. Specific examples of humic acids include humic acid, nitrohumic acid, ammonium humate, calcium humate, magnesium humate, ammonium nitrohumate, calcium nitrohumate, and magnesium nitrohumate. Other examples include fulvic acid, ammonium fulvic acid, and potassium fulvic acid. Humic acids preferably include one or both of humic acid or a salt thereof, and fulvic acid or a salt thereof. For specific examples of humic acid, refer to the description in paragraph 0020 of Japanese Patent Publication No. 2023-134372.

[0036] (Solid content concentration of humic acid extract) In the production of humic acid-containing powder, as described later, it is preferable that the solid content concentration of the humic acid extract be within an appropriate range from the viewpoint of production efficiency and drying efficiency. "Solid content concentration" refers to the components that remain after water is evaporated from the humic acid extract. The solid content concentration of the humic acid extract is preferably 5 to 60% by mass, more preferably 10 to 40% by mass. Using a humic acid extract with a solid content concentration of 5% by mass or more tends to allow the humic acid extract to be powdered with a relatively small amount of heat. This is desirable from the viewpoint of improving production efficiency and reducing manufacturing costs. Furthermore, using a humic acid extract with a solid content concentration of 60% by mass or less allows the humic acid extract to spread more easily on the disc surface in the manufacturing process using a disc dryer described later. This is thought to contribute to improved drying efficiency and suppression of powder clumping.

[0037] For methods of producing humic acid extract, refer to the descriptions in Patent Documents 1 and 2.

[0038] (Method for producing humic acid-containing powder) A humic acid-containing powder can be produced by drying the humic acid extract obtained as described above, or by drying a humic acid extract obtained by other methods. In this embodiment, a humic acid-containing powder with a compression degree of 5 to 20 can be produced by employing a manufacturing process using a disc dryer.

[0039] A disc dryer is a device that supplies a material to be dried onto a heated and rotating disc, dries it, and obtains non-volatile components. The non-volatile components generated on the disc as the material dries can be scraped off with a scraper to obtain powder from the dried material.

[0040] For reference, the basic structure of a disc dryer and a method for obtaining humic acid-containing powder from a humic acid extract using a disc dryer will be explained based on Figure 1. The disc dryer, as shown in Figure 1, comprises a rotatable disc 1 and a scraper 3. The disc 1 is typically made of metal. The disc 1 is heatable. Heating can be performed, for example, by using a hollow disc 1 and introducing heated steam into the interior of the disc 1. The scraper 3 is typically in contact with the disc 1. A humic acid extract 11 is supplied to the surface of a heated disk 1 that is rotating in the direction indicated by the arrow in Figure 1. The supplied humic acid extract 11 spreads thinly across the disk surface due to the centrifugal force caused by the rotation of disk 1, forming a thin film 13. As disk 1 is heated, the water in the thin film 13 evaporates, and solid humic acid precipitates on the surface of disk 1. By scraping off this solid with a scraper 3, a humic acid-containing powder 15 can be obtained.

[0041] For example, a disc dryer manufactured and sold by Nishimura Iron Works Co., Ltd. can be used.

[0042] In this embodiment, a disc dryer is used as the apparatus for powdering the humic acid extract, and by appropriately setting various process conditions during powdering, a humic acid-containing powder with a compression degree of 5 to 20 can be produced. The specific process conditions for producing humic acid-containing powder with a compression degree of 5 to 20 depend on the equipment, but for example, when using Nishimura Iron Works Co., Ltd.'s disc-type conductive heating liquid dryer (model: CD-500), the following process conditions can be adopted. • Disk heating temperature: For example, 120-140°C, preferably 125-140°C, more preferably 130-135°C • Disc rotation speed: For example, 1 to 10 revolutions / minute, preferably 1 to 5 revolutions / minute

[0043] <Method for producing humic acid-containing water> The humic acid-containing powder described above can be dissolved or dispersed in water to produce humic acid-containing water. This humic acid-containing water is preferably sprayed on the soil for soil improvement. When producing humic acid-containing water, the ratio of humic acid-containing powder to water is not particularly limited, but when spraying onto soil, it is preferable to dissolve or disperse 1 part by mass of humic acid-containing powder in 100 to 30,000 parts by mass of water.

[0044] <Methods for improving soil and promoting plant growth> By spraying the humic acid-containing water mentioned above onto the soil, it is possible to improve the soil, specifically making it suitable for plant growth. Similarly, plant growth can be promoted by applying the humic acid-containing water described above to plants. Specifically, plant growth can be promoted by spraying the humic acid-containing water onto soil in which plants are growing or planted. Various edible plants can be used as examples of plants.

[0045] While there are no particular limitations on the amount applied to the soil, considering the balance between obtaining sufficient soil improvement or plant growth promotion effects and cost, the amount of humic acid-containing water applied can be, for example, 10 to 50 t / ha. Alternatively, when converted to humic acid-containing powder, the application rate can be 0.01 to 0.1 kg / ha.

[0046] <Reference form: Humic acid containing material> This specification primarily describes humic acid-containing "powder" with a compressibility of 5 to 20. However, humic acid-containing materials that are not in powder form but have a compressibility of 5 to 20 may also be industrially useful. For example, a lump-shaped humic acid-containing material obtained by compressing humic acid-containing powder, with a compressibility of 5 to 20, may also be industrially useful.

[0047] Although embodiments of the present invention have been described above, these are merely examples, and various other configurations can be adopted. Furthermore, the present invention is not limited to the embodiments described above, and modifications and improvements that can achieve the objectives of the present invention are included within the scope of the present invention. [Examples]

[0048] Embodiments of the present invention will be described in detail based on examples and comparative examples. It should be noted that the present invention is not limited to these examples.

[0049] <Preparation of humic acid extract> The humic acid extract was prepared according to the following procedure. (1) 125 kg of lignite (bine) with a carbon content of 77% by mass was prepared by crushing it so that it could pass through a sieve with a mesh size of 250 μm. (2) Using a 500-liter stainless steel tank, 125 kg of the above-mentioned lignite and 157.5 kg of nitric acid with a concentration of 48% by mass were heated in a 70°C water bath and subjected to an oxidation reaction for approximately 1 hour. During this process, a small amount of defoaming agent (hydrophobic silica) was used to suppress excessive foaming. This oxidation reaction yielded a humic acid-containing liquid. (3) The obtained humic acid-containing liquid was dried at 105°C to obtain crude humic acid. The MI value of this crude humic acid was 2.20 (measured by the method described above). (4) To 100 kg of the obtained crude humic acid, approximately 900 L of 0.5 mol / L potassium hydroxide aqueous solution was added, and while monitoring with a pH meter, 1.0 mol / L potassium hydroxide aqueous solution was added to adjust the pH to 6.5. Then, a small amount of water was added to fine-tune the solid-liquid ratio to 1:10. (The solid-liquid ratio is defined as the amount of extraction solvent relative to the crude humic acid product. A solid-liquid ratio of 1:10 is defined as adding 1000 L of solvent to 100 kg of crude humic acid product.) (5) The liquid obtained in (4) above was heated at 80°C for 1 hour. In this way, humic acid was extracted with water to obtain a humic acid extract stock. (6) The above humic acid extract stock was centrifuged under centrifugal force (xg): 3000. The supernatant obtained therefrom was used as the humic acid extract in the production of the following humic acid-containing powder.

[0050] Incidentally, the humic acid concentration (which can be considered as the solid content concentration) of the obtained humic acid extract was 21% by mass.

[0051] <Manufacturing of humic acid-containing powder> [Examples 1-3] Using a disc-type conductive heating liquid dryer (model: CD-500) manufactured by Nishimura Iron Works Co., Ltd., water in a humic acid extract was evaporated under the following conditions to produce a humic acid-containing powder. • Heating the disc: The disc is heated by supplying 132°C superheated steam to the inside of the hollow disc structure. • Disc rotation speed: 3 rotations / minute

[0052] The production of humic acid-containing powder was carried out continuously for 10 hours using the CD-500 apparatus. The humic acid-containing powder obtained 1 hour after the start of production was designated as the humic acid-containing powder of Example 1, the humic acid-containing powder obtained 5 hours after the start of production was designated as the humic acid-containing powder of Example 2, and the humic acid-containing powder obtained 8 hours after the start of production was designated as the humic acid-containing powder of Example 3.

[0053] [Comparative Example 1] A humic acid-containing powder manufactured by a certain company (different from Denka Co., Ltd.) was obtained from the market. This powder was used as the humic acid-containing powder for Comparative Example 1.

[0054] <Measurement of loose and stiff bulk density, and calculation of compressibility> The following measurements were performed using a PT-X powder tester manufactured by Hosokawa Micron Corporation. [looseness density] Following the instructions included with the Powder Tester PT-X, humic acid-containing powder was dropped into a dedicated cup (100cc capacity) by gravity. The mass of the humic acid-containing powder when it filled the cup was then measured. Subsequently, the density was calculated based on the measured mass and the cup's capacity. Three measurements were taken, and the average of the three measurements was used as the loose bulk density. [Firmness and bulk density] After measuring the loose bulk density, the humic acid-containing powder was allowed to fall naturally into a special cup while tapping it 180 times per 180 seconds. The mass of the humic acid-containing powder filled in the cup after tapping was then measured. Subsequently, the density was calculated based on the measured mass of the humic acid-containing powder and the volume of the cup. Three measurements were performed, and the average of the three measurements was adopted as the firm bulk density. [Compression level] The measured looseness density is ρ A , firm bulk density ρ P When this is the case, {(ρ P -ρ A ) / ρ P The degree of compression was calculated using the formula} × 100.

[0055] <Measurement of particle size distribution> The particle size distribution was measured using a dry method with a laser diffraction / scattering particle size distribution analyzer, model LA-960 (manufactured by HORIBA). For the measurement, the refractive index was set to 1.81. The air pressure was set to 0.40 MPa. Under these conditions, the particle size distribution (volume basis) of the powders of each example and comparative example was automatically measured under atmospheric conditions. From the obtained particle size distribution, D 10 , D 50 and D 90 The value of was calculated. Also, based on these values ​​(D 50 -D 10 ) / D 50 The value and (D 90 -D 50 ) / D 50 The value was calculated.

[0056] <Measuring moisture content> The moisture content was measured using a halogen moisture meter HX204 (Mettler-Toledo). The drying temperature was set to 105°C, and the moisture content was automatically measured using 1 g of powder from each example or comparative example. Three measurements were taken, and the average of the three measurements was adopted as the moisture content.

[0057] <Measurement of Melanic Index (MI)> The melanic index (MI) of the humic acid-containing powder of Example 1 was measured using the method described above. The MI was 2.2.

[0058] <Evaluation: Fluidity of humic acid-containing powder> I followed these steps. (1) 10 g of humic acid-containing powder was placed in a stainless steel container with a flat bottom (the flat surface having an area of ​​at least 50 mm in width and 60 mm in depth), as shown in Figure 2. The powder was then leveled so that the surface of the powder was flat within the 50 mm wide x 60 mm deep area. (2) The container was tilted at a speed of 1° / second. The angle of the bottom surface of the container relative to the horizontal plane was measured when all the powder had flowed out. At this time, in order to prevent the powder that initially flowed out from accumulating at the mouth of the container and obstructing the subsequent flow of powder, the stainless steel container was placed on a stand so that the edge of the stand and the mouth of the container were at approximately the same level before the container was tilted. (3) Measurements were taken three times for each powder. The fluidity was evaluated by the average of the three angles obtained. A smaller value indicates better powder fluidity.

[0059] <Evaluation: Stability of packaged humic acid-containing powder> The evaluation was performed using the following procedure. (1) 250g of humic acid-containing powder was gently filled into a resealable plastic bag measuring 200mm wide x 280mm long, and the zipper was closed. A plastic bag containing humic acid-containing powder was thus prepared. In order to carry out (2) below, 27 plastic bags containing humic acid-containing powder were prepared for each type of humic acid-containing powder. (2) Poly bags containing humic acid powder were stacked in three layers, with 9 bags per layer (3x3), as shown in Figure 3. When the bags could be stacked stably and flat, it was evaluated as "good," and when the powder inside the bags was compressed, causing tilting and making it difficult to stack them stably, it was evaluated as "bad."

[0060] The various pieces of information are summarized in the table below. In Examples 2 and 3, D 50Values ​​related to particle size distribution, such as those mentioned above, have not been measured. However, common sense dictates that the particle size distributions of Examples 2 and 3 are not significantly different from those of Example 1.

[0061] [Table 1]

[0062] As shown in Table 1, the humic acid-containing powders of Examples 1 to 3, which had a compressibility in the range of 5 to 20, exhibited better powder fluidity compared to the humic acid-containing powder of Comparative Example 1, which had a compressibility greater than 20. Furthermore, the humic acid-containing powders of Examples 1-3, when packaged, could be stably stacked.

[0063] This application claims priority based on Japanese Patent Application No. 2023-190591, filed on 8 November 2023, and incorporates all of its disclosures herein. [Explanation of Symbols]

[0064] 1 disc 3. Scraper 11 Humic acid extract 13 Thin film 15 Humic acid containing powder

Claims

1. A humic acid-containing powder with a compression degree of 5 to 20, The median diameter D 50 is 10 to 200 μm. The melanic index is between 2 and 5. A humic acid-containing powder with a moisture content of 15% by mass or less.

2. The humic acid-containing powder according to claim 1, Looseness density is 0.2-0.5 g / cm ３ It is a humic acid-containing powder.

3. A method for producing humic acid-containing water, comprising dissolving or dispersing the humic acid-containing powder described in claim 1 or 2 in water to produce humic acid-containing water.

4. A method for improving soil, comprising spraying humic acid-containing water produced by the manufacturing method described in claim 3 onto the soil.

5. A method for promoting plant growth, comprising supplying plants with humic acid-containing water produced by the manufacturing method described in claim 3.

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