Water-retaining material for agriculture and horticulture, method for manufacturing the same, and soil composition

Abstract

To provide a water-retaining material for agriculture and horticulture that can reduce environmental impact and has excellent water retention properties, as well as a method for manufacturing the same. [Solution] The water-retaining material for agriculture and horticulture contains granules containing alkaline earth metal carbonate and blast furnace slag. The granules have first particles containing carbonate, second particles containing blast furnace slag that is at least partially hardened, and pores, with the first and second particles bound together. The method for manufacturing the water-retaining material for agriculture and horticulture includes the steps of: contacting a water-containing raw material containing waste containing alkaline earth metal oxide and water with a CO2-containing gas to obtain a carbon oxide containing alkaline earth metal carbonate; and mixing the carbon oxide, blast furnace slag fine powder and water, and granulating to obtain a granule.

Description

[Technical Field]

[0001] This disclosure relates to water-retaining materials for agriculture and horticulture, methods for producing the same, and soil compositions. [Background technology]

[0002] Water-retaining materials are used to enhance the water-retention capacity of soil used for plant germination and growth. Known water-retaining materials include water-absorbing polymers and natural materials. For example, Patent Document 1 proposes a water-retaining material for agricultural use that does not inhibit plant growth, comprising a vinyl alcohol-based polymer and inorganic particles. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2021-103957 [Overview of the project] [Problems that the invention aims to solve]

[0004] The water-retaining material described in Patent Document 1 requires a synthesis process using various organic substances to prepare a vinyl alcohol-based polymer, making it difficult to reduce the environmental impact. Therefore, this disclosure provides a water-retaining material for agriculture and horticulture that can reduce the environmental impact and has excellent water-retaining properties, as well as a method for producing the same. Furthermore, by including such a water-retaining material for agriculture and horticulture, a soil composition useful as soil for agriculture and horticulture is provided. [Means for solving the problem]

[0005] One aspect of this disclosure provides a water-retaining material for agriculture and horticulture, comprising granules containing alkaline earth metal carbonates and blast furnace slag. The granules contain blast furnace slag having latent hydraulic properties and alkaline earth metal carbonates not having latent hydraulic properties. Such granules can adequately retain moisture. Furthermore, they contain blast furnace slag, a by-product of the steel manufacturing process. Therefore, this water-retaining material for agriculture and horticulture, comprising these granules, can reduce environmental impact and has excellent water retention properties.

[0006] One aspect of this disclosure is the provision of a soil composition comprising the above-mentioned water-retaining material for agricultural and horticultural use and soil. This soil composition is useful as soil for agricultural and horticultural use because it contains the above-mentioned water-retaining material for agricultural and horticultural use which has excellent water retention properties.

[0007] One aspect of this disclosure provides a method for manufacturing a water-retaining material for agriculture and horticulture, comprising the steps of: contacting a hydrated raw material containing waste containing alkaline earth metal oxides and water with a CO2-containing gas to obtain a carbon oxide containing alkaline earth metal carbonates; and mixing the carbon oxide with blast furnace slag fine powder and water, and granulating the mixture to obtain granules. In this manufacturing method, since a carbon oxide containing carbonates is obtained by contacting a hydrated raw material containing waste with a CO2-containing gas, the amount of CO2 emitted can be reduced. Furthermore, blast furnace slag fine powder, a by-product of the steel manufacturing process, is used. Therefore, it is possible to reduce the environmental burden. In addition, the granules obtained by mixing blast furnace slag fine powder, which has latent hydraulic properties, carbon oxide containing alkaline earth metal carbonates that do not have latent hydraulic properties, and water can sufficiently retain moisture. Therefore, the above manufacturing method makes it possible to produce a water-retaining material for agriculture and horticulture that is both environmentally friendly and has excellent water retention properties. [Effects of the Invention]

[0008] This disclosure provides a water-retaining material for agriculture and horticulture that can reduce environmental impact and has excellent water retention properties, as well as a method for producing the same. Furthermore, by including such a water-retaining material for agriculture and horticulture, it is possible to provide a soil composition that is useful as soil for agriculture and horticulture. [Brief explanation of the drawing]

[0009] [Figure 1] This is a cross-sectional view showing an example of granules contained in water-retaining materials for agriculture and horticulture. [Figure 2] (A) is a graph showing the relationship between the pore diameter and cumulative pore volume (the cumulative value obtained by accumulating the volume of each pore from the largest pore diameter) of the granules of Example 1. (B) is a graph showing the relationship between the pore diameter and log differential pore volume (dV / d(logD)) of the granules of Example 1. [Figure 3] (A) is a graph showing the relationship between the pore diameter and cumulative pore volume (the cumulative value obtained by accumulating the volume of each pore from the largest pore diameter) of the mesalite of Comparative Example 3. (B) is a graph showing the relationship between the pore diameter and log differential pore volume (dV / d(logD)) of the mesalite of Comparative Example 3. [Figure 4] This graph plots the mass change rate α for Example 1-2 and Comparative Examples 1-1, 2-1, and 3-1, each containing 5 parts by mass of water-retaining material. [Figure 5] This graph plots the mass change rate α for Examples 1-3 and Comparative Examples 1-2, 2-2, and 3-2, each containing 10 parts by mass of water-retaining material for agricultural and horticultural use. [Figure 6] This graph plots the mass change rate α for Reference Example 1, which does not include water-retaining material for agricultural and horticultural use, and for Example 1-1, which includes 5 parts by mass of water-retaining material. [Figure 7] (A) is a photograph showing Nemophila (1 day after germination) that germinated using the soil composition of Example 1-1. (B) is a photograph showing Nemophila (2 days after germination) that germinated using the soil composition of Example 1-1. [Modes for carrying out the invention]

[0010] Embodiments of this disclosure will be described below, with reference to the drawings as appropriate. However, the following embodiments are illustrative for the purpose of illustrating this disclosure and are not intended to limit this disclosure to the following. In the description, the same reference numerals will be used for elements that are the same or have the same function, and redundant descriptions will be omitted as appropriate. The numerical ranges illustrated by "a~b" are numerical ranges that include a and b, with a lower limit being a and b as the upper limit being b. The disclosure also includes the cases in which the upper or lower limit of each numerical range is replaced with the numerical values ​​of any embodiment. When multiple materials are illustrated, one of them may be used alone or in combination with others.

[0011] Embodiments of this disclosure are described below. However, the following embodiments are illustrative for the purpose of explaining this disclosure and are not intended to limit this disclosure to the following. In the description, the same reference numerals are used for elements that are the same or have the same function, and redundant explanations are omitted where necessary. Also, unless otherwise specified, positional relationships such as up, down, left, and right are based on the positional relationship based on the orientation of the reference numerals shown in the drawings. The dimensional ratios of each element are not limited to the ratios shown. The numerical ranges illustrated as "a~b" are numerical ranges that include a and b, with a lower limit being a and an upper limit being b. The upper or lower limit of each numerical range is replaced with the numerical value of any embodiment, and is also included in this disclosure when it is replaced with the upper or lower limit of another numerical range. When multiple materials are illustrated, one of them may be used alone, or multiple may be used in combination.

[0012] <Water-retaining material for agriculture and horticulture> A water-retaining material for agricultural and horticultural use according to one embodiment comprises a granulated product containing an alkaline earth metal carbonate and blast furnace slag. The term "for agricultural and horticultural use" means that the material is used for both agricultural and horticultural applications. The alkaline earth metal carbonate may comprise at least one of CaCO₃ and MgCO₃, and may comprise CaCO₃. The water-retaining material for agricultural and horticultural use may comprise particles containing an alkaline earth metal carbonate. The content of the alkaline earth metal carbonate in the granulated product, based on 100 parts by mass of the total granulated product, may be 35 parts by mass or more, 40 parts by mass or more, 50 parts by mass or more, or 60 parts by mass or more. The content of the alkaline earth metal carbonate in the granulated product, based on 100 parts by mass of the total granulated product, may be 80 parts by mass or less, 75 parts by mass or less, or 70 parts by mass or less. The content of the alkaline earth metal carbonate in the granulated product, based on 100 parts by mass of the total granulated product, may be 35 to 80 parts by mass.

[0013] The blast furnace slag may be obtained by pulverizing granulated blast furnace slag, which is prepared by quenching molten slag discharged from a blast furnace in the steel manufacturing process with water or the like to form a vitreous material. By including such a by-product, the water-retaining material for agricultural and horticultural use can reduce environmental load. The blast furnace slag may, for example, be ground granulated blast furnace slag for concrete specified in JIS A 6206:2013. Blast furnace slag is a type of latent hydraulic material, and hardens via a hydration reaction when mixed with water in the presence of a stimulant (e.g., an alkali, sulfate, etc.).

[0014] Blast furnace slag may be at least partially hardened. For example, the granulated product may comprise a hardened product and an unhardened product of blast furnace slag. By hardening a part of the blast furnace slag, the granulated product can maintain a pore structure. Thereby, water retention can be sufficiently enhanced. The content of blast furnace slag (the total of both unhardened product and hardened product, if both are included) in the granulated product may be 20 parts by mass or more, 25 parts by mass or more, or 30 parts by mass or more, based on 100 parts by mass of the entire granulated product. The content of blast furnace slag (the total of both unhardened product and hardened product, if both are included) in the granulated product may be 65 parts by mass or less, 60 parts by mass or less, 50 parts by mass or less, or 40 parts by mass or less, based on 100 parts by mass of the entire granulated product. The content of blast furnace slag (the total of both unhardened product and hardened product, if both are included) in the granulated product may be 20 to 65 parts by mass, based on 100 parts by mass of the entire granulated product. Unless otherwise specified, "parts by mass" in the present specification refers to a value on a dry basis. The value on a dry basis can be calculated from the mass after drying the agricultural and horticultural water-retaining material at 105°C for 24 hours to remove adhering water.

[0015] Alkaline earth metal carbonates are not latent hydraulic materials and do not harden even when mixed with water. In contrast, blast furnace slag is a latent hydraulic material. Such a granulated product comprising a component having latent hydraulicity and a component having no latent hydraulicity in the above ratio can achieve both strength and water retention at a sufficiently high level.

[0016] The granulated product may comprise latent hydraulic materials other than blast furnace slag. Examples of such latent hydraulic materials include pozzolanic substances such as coal ash fly ash. The granulated product may comprise components other than alkaline earth metal carbonate and blast furnace slag. For example, it may comprise at least one selected from the group consisting of alkaline earth metal sulfates, alkaline earth metal hydroxides, alkaline earth metal oxides, and SiO2. The sulfate may comprise CaSO4, the hydroxide may comprise Ca(OH)2, and the oxide may comprise CaO, respectively.

[0017] When the total granules are measured in 100 parts by mass, the CaCO3 content may be 10 parts by mass or more, 15 parts by mass or more, 20 parts by mass or more, 25 parts by mass or more, 30 parts by mass or more, or 35 parts by mass or more. When the total granules are measured in 100 parts by mass, the CaCO3 content may be 60 parts by mass or less, 55 parts by mass or less, 50 parts by mass or less, or 45 parts by mass or less. When the total granules are measured in 100 parts by mass, the CaCO3 content may be 10 to 60 parts by mass. Horticultural water-retaining materials containing such granules are sufficiently suitable for plant germination and growth. Furthermore, since it can be prepared using waste containing CaO, CO2 emissions and manufacturing costs can be significantly reduced. In this case, alkaline earth metal carbonates may be contained in the carbon oxides of the waste containing CaO. Examples of waste containing CaO include lime calcination dust, cement clinker dust, by-product slaked lime, recycled cement, concrete sludge, and waste concrete.

[0018] When the total granules are measured in 100 parts by mass, the SiO2 content may be 5 parts by mass or more, 8 parts by mass or more, 10 parts by mass or more, or 12 parts by mass or more. When the total granules are measured in 100 parts by mass, the SiO2 content may be 25 parts by mass or more, 20 parts by mass or more, or 18 parts by mass or more. When the total granules are measured in 100 parts by mass, the SiO2 content may be 5 to 25 parts by mass. Horticultural water-retaining materials containing such granules are sufficiently suitable for plant germination and growth. Furthermore, since they can be prepared using waste materials such as lime calcination dust, cement clinker dust, by-product slaked lime, recycled cement, concrete sludge, or waste concrete, the environmental burden can be further reduced.

[0019] When the total granules are considered to be 100 parts by mass, the total content of CaCO3 and SiO2 may be 40-80 parts by mass, 45-70 parts by mass, or 50-60 parts by mass. Horticultural water-retaining materials containing such granules are sufficiently suitable for plant germination and growth. Furthermore, since they can be prepared using waste containing CaO, the environmental impact can be further reduced.

[0020] The water-retaining material for agriculture and horticulture may consist only of the granules described above, or it may contain components other than the granules described above. For example, it may contain other water-retaining materials, blast furnace slag powder, or carbon oxide itself. From the viewpoint of ensuring sufficiently high water retention, the content of granules in the water-retaining material for agriculture and horticulture may be 70 parts by mass or more, 80 parts by mass or more, 90 parts by mass or more, or 95 parts by mass or more, when the total amount of the water-retaining material for agriculture and horticulture is 100 parts by mass.

[0021] When 100 parts by mass of a soil composition prepared by mixing 90 parts by mass of culture soil with 10 parts by mass of a water-retaining material for agriculture and horticulture is mixed, and 100 parts by mass of water is added to this composition and left to stand in an environment of 20°C and 60 RH, the mass change rate α calculated by the following formula (1) may be maintained at -40% or more, or -38% or more, for 100 days. Here, "maintain" means that the above numerical range is continuously satisfied for 100 days. Such water-retaining materials and soil compositions for agriculture and horticulture have excellent water retention properties and are particularly suitable for plant germination and growth. In the following formula (1), W0 represents the mass of the soil composition immediately after watering, and Wt represents the mass of the soil composition after being left to stand for t days. Mass change rate α(%)=(Wt-W0) / W0 (1)

[0022] When 100 parts by mass of a soil composition prepared by mixing 80 parts by mass of culture soil with 20 parts by mass of a water-retaining material for agriculture and horticulture, and 100 parts by mass of water are added to this composition and left standing at 20°C and 60 RH%, the mass change rate α1 calculated by the following formula (2) may be maintained at -35% or more, or -30% or more, for 100 days. Such a water-retaining material and soil composition for agriculture and horticulture has superior water retention and is more suitable for plant germination and growth. W0 and Wt in the following formula (2) are the same as in formula (1). Mass change rate α1(%)=(Wt-W0) / W0 (2)

[0023] The potting soil used in the water-retaining material for agriculture and horticulture may be commercially available potting soil. When 100 parts by mass of water are added to 100 parts by mass of potting soil and left standing in an environment of 20°C and 60 RH, the rate of mass change α0 may be maintained at 0.95 or less, or 0.90 or less, for 100 days. α1 / α0 may be maintained at 0.85 or less, or 0.80 or less. α0 is a value calculated in the same manner as α and α1. Such water-retaining materials and soil compositions for agriculture and horticulture have excellent water retention properties and are particularly suitable for plant germination and growth.

[0024] The fine particle content of water-retaining materials for agriculture and horticulture may be 9.0% or less, 8.0% or less, 6.0% or less, or 4.0% or less, from the viewpoint of ensuring good drainage. For example, the fine particle content may be 0.5% or more, or 1.0% or more. The fine particle content can be measured in accordance with JIS A 1103:2014 "Test Method for Fine Particle Content of Aggregates".

[0025] The coarseness ratio of water-retaining material for agriculture and horticulture may be 3.0 or higher, 3.1 or higher, 3.2 or higher, 3.3 or higher, 3.4 or higher, 3.5 or higher, 3.6 or higher, or 3.7 or higher. This is presumed to sufficiently increase the strength and adequately suppress the collapse of the granulated material. The coarseness ratio may be 5.0 or lower, 4.5 or lower, or 4.0 or lower. The coarseness ratio can be measured in accordance with JIS A 1102:2014 "Test method for sieving aggregates".

[0026] The mass fraction of horticultural water-retaining material that remains between a series of sieves, measured in accordance with JIS A 1102:2014 "Test Method for Sieving Aggregates," may, for example, satisfy the numerical range specified in the "Crushed Sand" column of "Table 4 - Particle Size" in "5.3 Particle Size and Coarseness" of JIS A 5005:2020 "Crushed Stone and Crushed Sand for Concrete." Alternatively, the mass fraction of material that remains between the series of sieves may satisfy the numerical range in Table 1 below.

[0027] [Table 1]

[0028] The water absorption of the water-retaining material for agriculture and horticulture may be, for example, 15% or more, 18% or more, or 20% or more. The water absorption may be, for example, 30% or less. The surface-dry density of the water-retaining material for agriculture and horticulture is 1.30 g / cm 3 or more, 1.50 g / cm 3 or more, 1.80 g / cm 3 or more, or 1.90 g / cm 3 or more. The surface-dry density of the water-retaining material for agriculture and horticulture is 2.70 g / cm 3 or less, 2.50 g / cm 3 or less, or 2.30 g / cm 3 or less. The absolute dry density of the water-retaining material for agriculture and horticulture is 1.10 g / cm 3 or more, 1.30 g / cm 3 or more, or 1.50 g / cm 3 or more. The absolute dry density of the water-retaining material for agriculture and horticulture is 2.30 g / cm 3 or less, 2.10 g / cm 3 or less, or 1.80 g / cm 3 or less. The water absorption, surface-dry density and absolute dry density can be measured in accordance with JIS A 1109:2020 "Method of test for density and water absorption of fine aggregate".

[0029] The water-retaining material for agriculture and horticulture may contain moisture. In the present specification, the water content of the water-retaining material for agriculture and horticulture (mass%) is defined as the content of water relative to 100 parts by mass of dry mass after drying the water-retaining material for agriculture and horticulture at 105°C for 24 hours to remove attached water. This water content can be measured in accordance with JIS A 1125:2015 "Testing method for moisture content of aggregate and testing method for surface moisture content based on moisture content". The water content of the water-retaining material for agriculture and horticulture may be 10 mass% or more, 15 mass% or more, 20 mass% or more, or more than 21 mass%. The water content may be 35 mass% or less, 30 mass% or less, or 25 mass% or less.

[0030] Figure 1 shows a cross-section of an example of granules contained in a water-retaining material for agriculture and horticulture. The granules 10 include first particles 11 containing alkaline earth metal carbonate and second particles 12 containing blast furnace slag. The first particles 11 may be waste carbon oxides. In addition to the alkaline earth metal carbonate mentioned above, the first particles 11 may contain at least one selected from the group consisting of alkaline earth metal sulfate, alkaline earth metal hydroxide, alkaline earth metal oxide, and SiO2. A portion of the blast furnace slag contained in the second particles 12 (e.g., the surface) may be hardened blast furnace slag, while other portions (e.g., the interior) may be unhardened. The first particles 11 and the second particles 12 are bound together at the binding portion 20. At the binding portion 20, the first particles 11 and the second particles 12 may be bound together by hardened blast furnace slag.

[0031] The granulated material 10 is porous and has pores 30. The pores 30 are of a size that can be detected by mercury intrusion. The pores 30 may be surrounded by first particles 11 and second particles 12. The pores 30 may include open pores and closed pores. By having pores 30 of an appropriate size, the granulated material 10 can have sufficiently high water retention.

[0032] The cumulative pore volume of granules 10 with a pore diameter of 100 nm or less may be 0.060 mL / g or more, 0.070 mL / g or more, 0.080 mL / g or more, or 0.090 mL / g or more. Granules 10 containing a large number of relatively small pores in this way have sufficiently high water absorption. The cumulative pore volume of granules 10 with a pore diameter of 100 nm or less may be 0.400 mL / g or less, 0.300 mL / g or less, 0.200 mL / g or less, or 0.150 mL / g or less. The cumulative pore volume of granules 10 with a pore diameter of 100 nm or less may be 0.060 to 0.300 mL / g.

[0033] The total cumulative pore volume of the granules 10 may be 0.200 ml / g or less, 0.180 ml / g or less, or 0.160 ml / g or less. This is presumed to sufficiently suppress the collapse of the granules 10 and the collapse of the pores. The total cumulative pore volume of the granules 10 may be 0.060 ml / g or more, 0.070 ml / g or more, 0.080 ml / g or more, or 0.090 ml / g or more. The total cumulative pore volume of the granules 10 may be between 0.060 and 0.200 ml / g. The ratio of the cumulative pore volume of pores with a diameter of 100 nm or less to the total cumulative pore volume may be 0.3 or more, 0.4 or more, or 0.5 or more. This makes it possible to achieve a high level of both high water absorption and strength in the granules 10. This ratio may be 0.9 or less, 0.8 or less, or 0.7 or less.

[0034] In the pore size distribution of the granules 10, the pore size at the peak position of the maximum pore quantity may be 100 nm or less, 80 nm or less, 60 nm or less, 40 nm or less, or 30 nm or less. This allows the strength of the granules 10 to be sufficiently high. The pore size at the peak position of the maximum pore quantity may be 5 nm or more, 10 nm or more, or 15 nm or more. This allows the water absorption of the granules 10 to be further increased. The pore size at the peak position of the maximum pore quantity may be between 5 and 100 nm.

[0035] The pore size distribution, total pore volume, and cumulative pore volume of a specific pore size range described herein can be measured using a mercury porosimeter. The measurement conditions can be as described in the examples.

[0036] The average particle size of the granulated material may be 0.4 to 5.0 mm, or 1.0 to 3.0 mm. In this specification, the average particle size is the particle diameter at which the mass fraction is 50% in the particle size volume curve calculated using the particle size distribution measured in accordance with JIS A 1102:2014 "Test Method for Sieving Aggregates".

[0037] <Method for manufacturing water-retaining materials for agriculture and horticulture> A method for producing a water-retaining material for agriculture and horticulture according to one embodiment includes a carbonation step of contacting a water-containing raw material containing waste containing an alkaline earth metal oxide and water with a CO2-containing gas to obtain a carbon oxide containing an alkaline earth metal carbonate, and a granulation step of mixing the carbon oxide with blast furnace slag and water, and granulating it to obtain a granulated product. The alkaline earth metal oxide may be CaO. The waste containing CaO may include at least one selected from the group consisting of lime calcination dust, cement clinker dust, by-product slaked lime, concrete sludge, and waste concrete sludge. The lime calcination dust may include dust collected and recovered by a dust collector in a calcination kiln when calcining limestone. The cement clinker dust may include dust contained in the extraction gas of a cement kiln. The by-product slaked lime may include, for example, by-product slaked lime produced in the acetylene gas production process by the calcium carbide method. By using such waste materials, the manufacturing costs of water-retaining materials for agriculture and horticulture can be significantly reduced.

[0038] Waste containing CaO may contain at least one selected from the group consisting of Ca(OH)2, CaCO3, CaSO4, and SiO2, and may contain all of these. The CaO content per 100 parts by mass of dry waste may be 15 parts by mass or more, 20 parts by mass or more, 25 parts by mass or more, 30 parts by mass or more, 40 parts by mass or more, or 45 parts by mass or more. The above CaO content may be less than 100 parts by mass, 75 parts by mass or less, 70 parts by mass or less, 65 parts by mass or less, or 60 parts by mass or less.

[0039] If the waste containing CaO also contains Ca(OH)2, the Ca(OH)2 content may be 0.3 parts by mass or more, 0.5 parts by mass or more, or 1.0 part by mass or more per 100 parts by mass of dry waste. The Ca(OH)2 content may be 10 parts by mass or less, 8 parts by mass or less, 5 parts by mass or less, or 4 parts by mass or less. If the waste containing CaO also contains CaCO3, the CaCO3 content may be 3 parts by mass or more, 5 parts by mass or more, or 10 parts by mass or more per 100 parts by mass of dry waste. The CaCO3 content may be 30 parts by mass or less, 25 parts by mass or less, or 20 parts by mass or less.

[0040] If the waste containing CaO also contains CaSO4, the CaSO4 content may be 1 part by mass or more, 2 parts by mass or more, 5 parts by mass or more, 10 parts by mass or more, or 15 parts by mass or more per 100 parts by mass of dry waste. The CaSO4 content may be 30 parts by mass or less, 25 parts by mass or less, or 20 parts by mass or less. If the waste containing CaO also contains SiO2, the SiO2 content may be 1 part by mass or more, 2 parts by mass or more, or 3 parts by mass or more per 100 parts by mass of dry waste. The SiO2 content may be 10 parts by mass or less, or 8 parts by mass or less.

[0041] Before or simultaneously with carbonation, water may be added to the alkaline earth metal oxide to prepare a hydrated raw material. The waste and water are mixed so that the water content is 30-80 parts by mass, 35-70 parts by mass, or 40-60 parts by mass per 100 parts by mass of the dry-based waste containing the alkaline earth metal oxide. This increases the proportion of water on the waste surface, thereby improving the carbonation rate. As a result, the amount of CO2 fixed can be increased, and the amount of CO2 emitted can be reduced. If the waste contains adhering water, the amount of water mixed in may be adjusted to achieve the above-mentioned water content.

[0042] Carbonation may be carried out by contacting a water-containing raw material with a CO2-containing gas. The CO2-containing gas may be, for example, exhaust gas from coal-fired power plants, cement plants, and waste incineration plants. The CO2 content in the exhaust gas may be 1 volume% or more under standard conditions, and may be 3-50 volume%, 5-40 volume%, or 8-30 volume%. These exhaust gases may be used as is for carbonation, or a highly concentrated (e.g., more than 50 volume%) CO2-containing gas recovered and concentrated from the exhaust gas may be used.

[0043] In the carbonation process, the water-containing raw material may be stirred while being brought into contact with a CO2-containing gas. This allows for a sufficiently high efficiency of CO2 fixation. Examples of stirring devices for stirring the water-containing raw material include stirring type mixers (ribbon mixers, Nauter mixers, etc.), container mixing type mixers (V-type mixers, etc.), mixing and conveying machines (screw feeders, etc.), moving bed reactors (kiln type, etc.), and stirred tank type reactors. In the carbonation process, the contact time between the water-containing raw material and the CO2-containing gas may be adjusted according to the CO2 content in the CO2-containing gas, the shape and size of the container used for the carbonation process, etc.

[0044] The carbonation rate of the carbon oxide obtained in the carbonation process may be 20% by mass, 30% or more by mass, 40% or more by mass, 50% or more by mass, 60% or more by mass, 70% or more by mass, or 80% or more by mass. The above carbonation rate may be less than 100% by mass, 98% or less by mass, 95% or less by mass, 90% or less by mass, or 85% or less by mass. If the carbonation rate is less than 100% by mass, CaO and Ca(OH)2, etc., which may be contained in the carbon oxide can act as stimulants in the granulation process and promote the hardening of the blast furnace slag. The carbonation rate in this specification is the ratio of the substance carbonated in the carbonation process to the total amount of carbonizable substance contained in the water-containing raw material. Specifically, it represents the proportion (by mass) of basic compounds (e.g., oxides containing alkaline earth metals, hydroxides, etc.) in the water-containing raw material that have been changed into carbon oxide.

[0045] The carbonation rate can be adjusted by the amount of water added when preparing the hydrated raw material, and the contact time between the hydrated raw material and the CO2-containing gas. The carbon oxide obtained in the carbonation process may contain alkaline earth metal oxides, alkaline earth metal hydroxides, alkaline earth metal sulfates, SiO2, etc., in addition to alkaline earth metal carbonates. The carbonate content in the carbon oxide may be 40-90% by mass, 50-80% by mass, or 60-70% by mass. The carbon oxide obtained in the carbonation process may be stored in a hopper or the like, or the carbonation process and granulation process may be carried out continuously without storage in a hopper or the like.

[0046] In the granulation process, granules may be obtained by stirring and granulating a mixture containing the carbon dioxide obtained in the carbonation process, blast furnace slag fine powder, and water. In other words, granules may be obtained by wet granulation in the granulation process. Blast furnace slag fine powder is a type of latent hydraulic material. Latent hydraulic materials do not harden simply by mixing with water, but harden by a hydration reaction when mixed with water in the presence of a stimulant (e.g., alkali, sulfate, etc.). On the other hand, carbon dioxide does not have latent hydraulic properties. Because such components are used, granules containing pores can be obtained.

[0047] When preparing the above mixture, the mixing ratio of carbon dioxide and blast furnace slag fine powder may be 35-80 parts by mass, 40-80 parts by mass, 50-75 parts by mass, or 60-70 parts by mass of carbon dioxide per 100 parts by mass of the total of carbon dioxide and blast furnace slag fine powder. The mixture may contain alkaline earth metal carbonates, SiO2, and stimulants. SiO2 may be present as calcium silicate compounds or aluminum silicate compounds. The presence of SiO2 promotes the pozzolanic reaction, forming hydrates and accelerating the development of strength. Examples of stimulants include hydroxides such as Ca(OH)2 and sulfates such as CaSO4.

[0048] In the granulation process, additives other than carbon oxide and blast furnace slag fine powder may be added. Examples of additives include binders, dispersants, and water-reducing agents to promote granulation. Examples of binders include pozzolanic substances such as fly ash and silicate mixtures. Examples of water-reducing agents include high-performance water-reducing agents, high-performance AE water-reducing agents, AE water-reducing agents, and fluidizing agents. Polyvinyl alcohol and water glass may also be added as additives. One of these additives may be used alone, or two or more may be used in combination.

[0049] In the granulation process, the water contained in the mixture may be water contained in the carbon dioxide and water derived from additives, or it may be water added separately. The water-containing raw material used in the carbonation process contains water, but at least a portion of this water may evaporate due to the heat generated by the carbonation reaction. The water content in the mixture in the granulation process may be 10 to 35 parts by mass, 15 to 30 parts by mass, or 20 to 25 parts by mass per 100 parts by mass of the dry mass of the mixture. By including water in such a ratio, the hardening reaction of the blast furnace slag fine powder can be advanced, and granules with appropriate pore size and strength can be obtained. The dry mass of the mixture refers to the mass after drying at 105°C for 24 hours to remove any adhering water.

[0050] The granulation process may be carried out using a stirring device. Examples of stirring devices include a three-one motor, a Hobart mixer, a high-speed mixer, and a Nauter mixer. The stirring temperature may be, for example, 1 to 50°C or 10 to 45°C. The stirring time may be 1 to 30 minutes or 5 to 20 minutes.

[0051] The particle size of the granules may be adjusted by the granulation conditions during the granulation process, or the particle size of the granules may be adjusted by a sieving process after the granulation process. In this way, a horticultural water-retaining material containing granules can be obtained. Any other process may be performed in addition to the above-mentioned process.

[0052] <Soil composition> A soil composition according to one embodiment includes the above-mentioned water-retaining material for agriculture and horticulture and soil. This soil composition may also be for agriculture and horticulture. As the soil, any soil that does not hinder plant germination and growth can be used as appropriate. The soil may be, for example, commercially available potting soil or potting soil.

[0053] The amount of water-retaining material for agriculture and horticulture in the soil composition may be 3 parts by mass or more, 5 parts by mass or more, or 10 parts by mass or more, based on 100 parts by mass of the entire soil composition. This allows the water-retaining capacity of the soil composition to be sufficiently high. The amount of water-retaining material for agriculture and horticulture in the soil composition may be 30 parts by mass or less. The soil composition may contain components other than soil and water-retaining material for agriculture and horticulture, such as fertilizers.

[0054] Although embodiments of this disclosure have been described above, this disclosure is not limited in any way to the embodiments described above. The embodiments described above include the following:

[0055] [1] A water-retaining material for agriculture and horticulture, comprising granules containing alkaline earth metal carbonates and blast furnace slag. [2] The granules comprising first particles containing the carbonate, second particles containing the blast furnace slag which is at least partially hardened, and pores, wherein the first particles and the second particles are bound together, the water-retaining material for agriculture and horticulture according to [1]. [3] The water-retaining material for agriculture and horticulture according to [1] or [2], wherein when 100 parts by mass of a soil composition is prepared by blending 10 parts by mass of the water-retaining material for agriculture and horticulture with 90 parts by mass of culture soil, 100 parts by mass of water is added to 100 parts by mass of the soil composition and the mixture is left standing in an environment of 20°C and 60 RH, the rate of change in mass is α, and when 100 parts by mass of water is added to 100 parts by mass of the culture soil and the mixture is left standing in the same environment, the rate of change in mass is α0, and α / α0 is maintained at 0.95 or less for 100 days. [4] A water-retaining material for agriculture and horticulture according to any one of [1] to [3], comprising a waste carbon oxide containing CaO, wherein the carbonate is contained in the carbon oxide. [5] The alkaline earth metal carbonate contains CaCO3, A water-retaining material for agriculture and horticulture according to any one of [1] to [4], wherein, when the entire granulated material is 100 parts by mass, the CaCO3 content is 10 to 60 parts by mass and the SiO2 content is 5 to 25 parts by mass. [6] The water-retaining material for agriculture and horticulture according to any one of [1] to [5], wherein the cumulative pore volume of the granules with a pore diameter of 100 nm or less is 0.060 ml / g or more. [7] A water-retaining material for agriculture and horticulture according to any one of [1] to [6], wherein the total cumulative pore volume of the granules is 0.200 ml / g or less. [8] The water-retaining material for agriculture and horticulture according to any one of [1] to [7], wherein the pore size distribution of the granules has a pore size of 100 nm or less at the position of the maximum peak of pore quantity. [9] A water-retaining material for agriculture and horticulture according to any one of [1] to [8], wherein the ratio of the cumulative pore volume of pores with a diameter of 100 nm or less to the total cumulative pore volume of the granules is 0.3 or more.

[10] A soil composition comprising a water-retaining material for agricultural and horticultural use described in any one of [1] to [9] above and soil.

[11] A process to obtain a carbon oxide containing alkaline earth metal carbonate by contacting a water-containing raw material containing waste containing alkaline earth metal oxides and water with a CO2-containing gas, A method for producing a water-retaining material for agriculture and horticulture, comprising the steps of mixing the aforementioned carbon oxide, blast furnace slag fine powder, and water, and granulating the mixture to obtain a granulated product.

[12] The method for producing a water-retaining material for agriculture and horticulture according to

[11] , wherein the waste comprises at least one selected from the group consisting of lime calcination dust, cement clinker dust, by-product slaked lime, concrete sludge, and waste concrete sludge. [Examples]

[0056] The contents of this disclosure will be described in more detail with reference to examples and comparative examples, but this disclosure is not limited to the following examples.

[0057] <Preparation of water-retaining materials for agriculture and horticulture> (Example 1) Lime calcined dust (Beckenbach furnace dust, manufactured by Ube Materials Co., Ltd.) having the composition shown in Table 2 was prepared. The units of the values ​​in Table 2 are "mass %". In Table 2, "ig.loss" is the loss on ignition, and indicates the total mass of organic components and water that volatilized by heating at 950°C. "f.CaO" indicates the free lime (free CaO) content.

[0058] [Table 2]

[0059] 10 kg of the aforementioned lime calcined dust (dry mass) and 5 kg of tap water were added to a 30 L ribbon mixer (Dalton Co., Ltd., RM20). While stirring, CO2 (carbon dioxide) was passed through at a flow rate of 100 L / min for 30 minutes to perform a carbonation treatment and obtain carbon dioxide. The CaCO3 content in the carbon dioxide was 66.2 parts by mass per 100 parts by mass of the dry mass of the carbon dioxide.

[0060] The carbon oxide obtained by the procedure described above was mixed with blast furnace slag fine powder (manufactured by Chiba Riverment Co., Ltd., product name: Riverment Gx) having the composition shown in Table 3 to obtain a mixture. At this time, the mixing ratio of carbon oxide to blast furnace slag fine powder was 65:35 by dry mass ratio.

[0061] [Table 3]

[0062] This mixture was placed in a 118L high-speed mixer (FS100, manufactured by Earth Technica Co., Ltd.) and mixed for 1 minute under conditions of agitator rotation speed of 133 rpm and chopper rotation speed of 3000 rpm. Then, tap water was measured out so that the water content was 23 parts by mass per 100 parts by mass of the dry mass of the above mixture. This tap water was added to the agitator over 1.0 minute while mixing for 1 minute under conditions of agitator rotation speed of 133 rpm and chopper rotation speed of 3000 rpm. Then, stirring was continued for 3 minutes to granulate and obtain granulated material (carbonate hardened material) (granulation time: total 4 minutes). This was used as the water-retaining material for agricultural and horticultural use in Example 1.

[0063] (Comparative Examples 1-3) The following comparative examples 1-3 were prepared as water-retaining materials for agricultural and horticultural use. Comparative Example 1: Perlite (commercially available product, manufactured by Tamiya Gardening Co., Ltd.) Comparative Example 2: Zeolite (commercially available product, manufactured by Kanuma Kogyo Co., Ltd.) Comparative Example 3: Mesalite (commercially available product, manufactured by Nippon Mesalite Industries Co., Ltd.)

[0064] <Evaluation of physical properties> The pore size distribution of the granules from Example 1 and the mesalite from Comparative Example 3 was measured. Specifically, a mercury intrusion porosimeter (Anton Paar Pore Master 60-GT) was used to measure the pore size range from 400,000 to 3.6 nm.

[0065] Figure 2(A) shows the relationship between the pore diameter and cumulative pore volume (the cumulative value obtained by accumulating the volumes of each pore, starting from the largest pore diameter) of the granules of Example 1. In the graph of Figure 2(A), the horizontal axis represents pore diameter (nm), and the vertical axis represents cumulative pore volume (mL / g). Figure 2(B) shows the relationship between the pore diameter and log differential pore volume (dV / d(logD)) of the granules of Example 1. In the graph of Figure 2(B), the horizontal axis represents pore diameter (nm), and the vertical axis represents dV / d(logD)(mL / g). Here, dV is the differential pore volume, and d(logD) is the logarithmic difference of the pore diameter D.

[0066] Figure 3(A) shows the relationship between the pore diameter and cumulative pore volume (the cumulative value obtained by accumulating the volumes of each pore, starting from the largest pore diameter) of the mesalite of Comparative Example 3. In the graph of Figure 3(A), the horizontal axis represents pore diameter (nm), and the vertical axis represents cumulative pore volume (mL / g). Figure 3(B) shows the relationship between the pore diameter and log differential pore volume (dV / d(logD)) of the mesalite of Comparative Example 3. In the graph of Figure 3(B), the horizontal axis represents pore diameter (nm), and the vertical axis represents dV / d(logD)(mL / g).

[0067] From the measurement results of the pore size distribution of the granules of Example 1 and the mesalite of Comparative Example 3, the cumulative pore volume of pores with a diameter of 100 nm or less, the total cumulative pore volume, and the pore size at the peak position of the maximum pore volume were determined. The results are shown in Table 4.

[0068] The coarseness, fineness, surface-dry density, moisture content, and water absorption rate of the granules from Example 1 were measured. The coarseness was measured in accordance with JIS A 1102:2014 "Test method for sieving aggregates". The fineness was measured in accordance with JIS A 1103:2014 "Test method for fineness of aggregates". The surface-dry density, oven-dry density, and water absorption rate were measured in accordance with JIS A 1109:2020 "Test method for density and water absorption rate of fine aggregates". The moisture content was measured in accordance with JIS A 1125:2015 "Test method for moisture content of aggregates and test method for surface moisture content based on moisture content". The mesalite from Comparative Example 3 was measured in the same manner. The results are shown in Tables 4 and 5.

[0069] [Table 4]

[0070] [Table 5]

[0071] As shown in Table 4, although the total cumulative pore volume of the granules from Example 1 was smaller than that of the mesalite from Comparative Example 3, the volume of small pores was greater in the granules from Example 1 than in Comparative Example 3. This confirmed that the granules from Example 1 contained a large number of fine pores. The ratio of the cumulative pore volume of pores with a diameter of 100 nm or less to the total cumulative pore volume of the granules from Example 1 was approximately 0.67. In contrast, the ratio for Comparative Example 3 was approximately 0.24.

[0072] <Evaluation of water retention> For evaluation purposes, potting soil (manufactured by Iris Ohyama Co., Ltd., product name: Potting Soil for Flowers and Vegetables) was prepared. Each water-retaining material from Example 1 and Comparative Examples 1-3 was mixed with this potting soil in the parts by mass shown in Table 6, and the soil compositions for each example and comparative example shown in Table 6 were prepared. In Reference Example 1, the potting soil was used as the soil composition as is.

[0073] [Table 6]

[0074] A polypropylene pot (bottom inner diameter: 12.5 cm, height: 18 cm, top opening diameter: 18 cm, mass: 195 g) was prepared. The bottom opening was sealed with a resin sheet, ensuring there were no openings other than the top. The soil compositions of Reference Example 1, each example, and each comparative example shown in Table 6 were placed in this pot. The mass of each soil composition placed in the pot was as shown in Table 6. 1000 g of water was poured into each pot, and the initial mass (W0) of the soil composition immediately after watering was measured. Subsequently, the pots were stored in a room maintained at 20°C and 60 RH%, and the mass (Wt) was measured at appropriate intervals. The mass change rate α (%) was calculated using the above formula (1). The results are shown in Table 7.

[0075] [Table 7]

[0076] Figure 4 shows a graph plotting the mass change rate α for Example 1-2 and Comparative Examples 1-1, 2-1, and 3-1, which contain 5 parts by mass of water-retaining material for agriculture and horticulture, from the results shown in Table 7. Figure 5 shows a graph plotting the mass change rate α for Example 1-3 and Comparative Examples 1-2, 2-2, and 3-2, which contain 10 parts by mass of water-retaining material for agriculture and horticulture, from the results shown in Table 7. As shown in Figures 4 and 5, it was confirmed that the water-retaining material for agriculture and horticulture in Example 1 has superior water retention properties compared to the water-retaining materials of each comparative example. Figure 6 shows a graph plotting the mass change rate α for Reference Example 1, which does not contain water-retaining material for agriculture and horticulture, and Example 1-1, which contains 5 parts by mass of water-retaining material, from the results shown in Table 7. As shown in Figure 6, it was confirmed that the water-retaining material for agriculture and horticulture in Example 1 can improve water retention even at a low ratio of 5 parts by mass. Next, using the mass change rate of Reference Example 1 as the baseline (α=α0), the ratio of the mass change rate α to the baseline (α / α0) was calculated. The results are shown in Table 8.

[0077] [Table 8]

[0078] As shown in Table 8, the α / α0 ratio for Examples 1-1, 1-2, and 1-3 remained below 1.0 throughout the 100-day evaluation period. This confirms that the water-retaining material of Example 1 can maintain its water retention over a long period of time. Comparative Examples 1-1 and 1-2, which used perlite in Comparative Example 1, initially exhibited water retention, but it was observed that their water retention rapidly decreased after about 50 days. Comparative Examples 2-1 and 2-2, which used zeolite in Comparative Example 2, and Comparative Examples 3-1 and 3-2, which used mesalite in Comparative Example 3, all showed almost no water retention.

[0079] <Plant germination test> Plant (Nemophila) germination tests were conducted using the soil compositions of Reference Example 1, Examples 1-1, 1-2, 1-3, and Comparative Examples 1-1, 1-2, 2-1, and 2-2. Approximately 140g of each soil composition was placed in a plastic pot, and the test was conducted to see if germination would occur under conditions of 20°C. During the test period, 30ml of water was added once a day. As a result, germination of Nemophila was confirmed within 3 days for all soil compositions of Reference Example 1, Examples 1-1 to 1-3, and Comparative Examples 1-1, 1-2, 2-1, and 2-2.

[0080] Figure 7(A) is a photograph showing Nemophila (1 day after germination) that germinated using the soil composition of Example 1-1. Figure 7(B) is a photograph showing Nemophila (2 days after germination) that germinated using the soil composition of Example 1-1. These test results confirm that the water-retaining material of Example 1, and the soil compositions of Examples 1-1, 1-2, and 1-3 are suitable for plant growth. [Explanation of Symbols]

[0081] 10...granules, 11...first particle, 12...second particle, 20...binding portion, 30...pores.

Claims

1. A water-retaining material for agriculture and horticulture, containing granules that include alkaline earth metal carbonates and blast furnace slag.

2. The granulated material comprises first particles containing the carbonate, second particles containing the blast furnace slag which is at least partially hardened, and pores, wherein the first particles and the second particles are bound together, as described in claim 1.

3. The water-retaining material for agriculture and horticulture according to claim 1 or 2, wherein when 100 parts by mass of water is added to 100 parts by mass of a soil composition obtained by blending 10 parts by mass of the water-retaining material for agriculture and horticulture with 90 parts by mass of culture soil, and the material is left standing in an environment of 20°C and 60 RH, the rate of mass change when this is α is defined as α0, and when 100 parts by mass of water is added to 100 parts by mass of the culture soil and the material is left standing in the same environment, α / α0 is maintained at 0.95 or less for 100 days.

4. A water-retaining material for agriculture and horticulture according to claim 1 or 2, comprising a waste carbon oxide containing CaO, wherein the carbonate is contained in the carbon oxide.

5. The carbonate of the aforementioned alkaline earth metal is CaCO3 ３ Includes, When the total mass of the granulated material is 100 parts, CaCO3 ３ The content is 10 to 60 parts by mass, and SiO ２ The water-retaining material for agriculture and horticulture according to claim 1 or 2, wherein the content of is 5 to 25 parts by mass.

6. The water-retaining material for agriculture and horticulture according to claim 1 or 2, wherein the cumulative pore volume of the granules with a pore diameter of 100 nm or less is 0.060 ml / g or more.

7. The water-retaining material for agriculture and horticulture according to claim 1 or 2, wherein the total cumulative pore volume of the granules is 0.200 ml / g or less.

8. The water-retaining material for agriculture and horticulture according to claim 1 or 2, wherein in the pore size distribution of the granules, the pore size at the position of the maximum peak of pore quantity is 100 nm or less.

9. The water-retaining material for agriculture and horticulture according to claim 1 or 2, wherein the ratio of the cumulative pore volume of pores with a diameter of 100 nm or less to the total cumulative pore volume of the granules is 0.3 or more.

10. A soil composition comprising the water-retaining material for agricultural and horticultural use described in claim 1 or 2 and soil.

11. A water-containing raw material containing waste containing alkaline earth metal oxides and water, and CO ２ A process of bringing the contained gas into contact with a carbon oxide containing an alkaline earth metal carbonate, A method for producing a water-retaining material for agriculture and horticulture, comprising the steps of mixing the aforementioned carbon oxide, blast furnace slag fine powder, and water, and granulating the mixture to obtain a granulated product.

12. The method for producing a water-retaining material for agriculture and horticulture according to claim 11, wherein the waste includes at least one selected from the group consisting of lime calcination dust, cement clinker dust, by-product slaked lime, concrete sludge, and waste concrete sludge.

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