Raw material for fertilizer, method for producing raw material for fertilizer, method for producing fertilizer, raw material for liquid fertilizer, and method for producing raw material for liquid fertilizer

Abstract

The present invention relates to a method for producing a raw material for a fertilizer, the method being characterized by subjecting glass to ion exchange using a molten salt containing potassium nitrate, cooling and solidifying the molten salt, and obtaining a salt containing potassium nitrate. The present invention also relates to a raw material for a fertilizer, which comprises a plurality of blocks. The raw material for a fertilizer is characterized in that: the proportion of water-soluble potassium is 40 wt% or more relative to the raw material for a fertilizer; the proportion of nitrate nitrogen is 11 wt% or more relative to the total amount of the raw material for a fertilizer; and when two blocks, each having a mass of 50-150 g, are sampled per 10 kg of the raw material for a fertilizer, the difference in the concentration of water-soluble potassium between the two blocks is 6.0 wt% or less and the difference in the concentration of nitrate nitrogen between the two blocks is 1.9 wt% or less.

Description

Fertilizer raw material and method for manufacturing fertilizer raw material, fertilizer manufacturing method, liquid fertilizer raw material and method for manufacturing liquid fertilizer raw material

[0001] The present invention relates to a method for producing a fertilizer raw material using a molten salt for chemical strengthening treatment, a fertilizer raw material, and a fertilizer production method. The present invention also relates to a liquid fertilizer raw material and a method for producing a liquid fertilizer raw material using the fertilizer raw material.

[0002] Glass that has been chemically strengthened by ion exchange or the like is used for the cover glass and display glass substrates of electronic devices such as mobile phones and smartphones.

[0003] Chemical strengthening by ion exchange is a process for improving glass strength by replacing metal ions contained in glass with metal ions having a larger ionic radius. Chemical strengthening is performed by exchanging sodium ions in the glass with potassium ions in the molten salt. Hereinafter, the "chemical strengthening by ion exchange" described above may be referred to simply as "ion exchange."

[0004] The sodium concentration in the molten salt obtained after the ion exchange treatment is higher than the sodium concentration in the molten salt before the ion exchange treatment. The resulting molten salt is usually discarded after cooling and solidifying the potassium nitrate-containing salt, which is crushed into small blocks. Patent Document 1 provides a new method for utilizing molten salt that would otherwise be discarded after chemical strengthening treatment, by regenerating the molten salt and making it usable again as molten salt for chemical strengthening, thereby reducing the burden on the environment.

[0005] International Publication No. 2015 / 080095

[0006] In recent years, in the process of manufacturing chemically strengthened glass, there has been a demand for measures to further reduce the burden on the environment, such as reducing waste generated in the manufacturing process.

[0007] Patent Literature 1 describes the reuse of molten salt after ion exchange treatment for the next ion exchange treatment. However, there are cases where not all of the molten salt after chemical strengthening treatment can be reused for the next chemical strengthening treatment, resulting in some molten salt being discarded. Therefore, in order to further reduce the burden on the environment, there is a need to reuse a larger amount of molten salt.

[0008] Therefore, the present invention has been made in view of the above-mentioned problems, and aims to reuse a larger amount of molten salt after chemical strengthening treatment by ion exchange and reduce the burden on the environment by processing the molten salt after ion exchange treatment so that it can be produced as a fertilizer raw material.

[0009] That is, the present invention relates to the following items <1> to <10>. <1> A method for producing a raw material for a fertilizer, comprising ion-exchanging glass with a molten salt containing potassium nitrate and cooling and solidifying the molten salt to obtain a potassium nitrate-containing salt. <2> A method for producing a raw material for a fertilizer according to item <1>, further comprising pulverizing the potassium nitrate-containing salt to produce the raw material for a fertilizer, wherein when the molten salt is cooled and solidified in the container for cooling and solidifying, the molten salt is cooled in the container, and at a depth intermediate between the bottom of the container and the liquid level of the molten salt, a temperature of a region of the molten salt in contact with the inner wall of the container is 345°C or higher and 355°C or lower, and a maximum temperature difference of the molten salt among any six points in the container is within a range of 120°C or lower. <3> The method for producing a fertilizer raw material according to <2>, wherein the difference in nitrate nitrogen concentration between 100 g of the potassium nitrate-containing salt present in a central region of a cross section parallel to the bottom, at a depth midway between the bottom of the container and the surface of the potassium nitrate-containing salt, and the difference in water-soluble potassium concentration between 100 g of the potassium nitrate-containing salt present in a central region of the surface at the surface is 1.9 wt% or less. <4> The method for producing a fertilizer raw material according to <1> or <2>, wherein, when the fertilizer raw material is sieved through a sieve conforming to JIS Z8801-1 and having a mesh size of 5.6 mm, the amount of material that passes through the sieve is 1 wt% or less of the input amount. <5> The method for producing a fertilizer raw material according to <1> or <2>, wherein, when the fertilizer raw material is sieved through a sieve conforming to JIS Z8801-1 and having a mesh size of 11.2 mm, the amount of material that passes through the sieve is less than 10 wt% of the input amount. <6> The method for producing a fertilizer raw material according to <1> or <2>, wherein the proportion of water-soluble potassium relative to the total weight of the potassium nitrate-containing salt is 40 wt% or more and the proportion of nitrate nitrogen relative to the total weight of the potassium nitrate-containing salt is 11 wt% or more. <7> The method for producing a fertilizer raw material according to <1> or <2>, wherein the molten salt further contains one or more salts selected from the group consisting of potassium carbonate, sodium carbonate, potassium bicarbonate, sodium bicarbonate, potassium phosphate, sodium phosphate, sodium nitrate, potassium hydroxide, and sodium hydroxide.<8> The fertilizer raw material obtained by the pulverization is composed of a plurality of lumps, and the volume of each of the lumps is 10,000 cm. ３ <9> The method for producing a fertilizer raw material according to <2>, wherein the volume of the container is 2,000,000 cm or less. ３ <10> A fertilizer raw material comprising a plurality of lumps, wherein the ratio of water-soluble potassium relative to the fertilizer raw material is 40 wt % or more and the ratio of nitrate nitrogen relative to the total weight of the fertilizer raw material is 11 wt % or more, and when two lumps, each having a mass of 50 g to 150 g, are collected per 10 kg of the fertilizer raw material, the difference in water-soluble potassium concentration between the two lumps is 6.0 wt % or less and the difference in nitrate nitrogen concentration is 1.9 wt % or less. <11> The fertilizer raw material according to <10>, wherein when sieved through a sieve conforming to JIS Z8801-1 and having a mesh size of 5.6 mm, the amount passing through the sieve is 1 wt % or less of the input amount. <12> The fertilizer raw material according to <10> or <11>, wherein when sieved through a sieve conforming to JIS Z8801-1 and having an opening of 11.2 mm, the amount of the raw material that passes through the sieve is less than 10 wt% of the input amount. <13> The fertilizer raw material according to <10> or <11>, wherein the ratio of sodium to the raw material for fertilizer is 1,000 ppm or more and 20,000 ppm or less. <14> The fertilizer raw material is a fertilizer raw material having a volume per lump of 10,000 cm3. ３ A fertilizer raw material according to <10> or <11>, which is the following: <15> A method for producing a fertilizer using the fertilizer raw material according to <10> or <11>. <16> A method for using a potassium nitrate-containing salt obtained after ion exchange of glass as a fertilizer raw material. <17> A method for producing a liquid fertilizer raw material, the method comprising sieving the fertilizer raw material according to any one of <10> to <14> through a sieve having an opening of 11.2 mm in accordance with JIS Z8801-1, and immersing the pass-through material in water. <18> A liquid fertilizer raw material comprising water and the pass-through material from the fertilizer raw material according to any one of <10> to <14> that passes through a sieve having an opening of 11.2 mm in accordance with JIS Z8801-1.

[0010] The method for producing a fertilizer raw material according to the present invention allows for the production of a fertilizer raw material from ion-exchanged molten salt, which has conventionally been discarded, and for the reuse of the molten salt. Furthermore, the method is extremely useful in that it allows for the reuse of a larger amount of molten salt after chemical strengthening by ion exchange, thereby reducing the burden on the environment.

[0011] Fig. 1 is a flow diagram showing one embodiment of a method for producing a fertilizer raw material and a method for producing a fertilizer according to the present invention. Fig. 2 is a schematic diagram showing a method for measuring a temperature difference and a method for collecting salt in Example 1 during cooling and solidifying of molten salt. Fig. 3 is a cross-sectional view in the xy plane showing a method for measuring a temperature difference and a method for collecting salt in Example 1 during cooling and solidifying of molten salt. (a) is a cross-sectional view in the xy plane at z = zero, (b) is a cross-sectional view in the xy plane at z = d / 2, and (c) is a cross-sectional view in the xy plane at z = d. Fig. 4 is a schematic diagram showing a method for measuring a temperature difference and a method for collecting salt in Examples 2 to 9 during cooling and solidifying of molten salt.

[0012] Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings. However, the present invention is not limited to these embodiments. Furthermore, when there are multiple embodiments, the present invention also includes those configured by combining the respective embodiments. Furthermore, the numerical values ​​include the range of rounding. In this specification, "water-soluble potassium" refers to potassium oxide (K ２ O), and "nitrate nitrogen" refers to potassium that exists in the nitrate (NO ３ ) means nitrogen present in the state

[0013] <Method for producing a fertilizer raw material> The present invention relates to a method for producing a fertilizer raw material, which comprises ion-exchanging glass with a molten salt containing potassium nitrate and cooling and solidifying the molten salt to obtain a potassium nitrate-containing salt.

[0014] FIG. 1 shows an embodiment of a method for producing a raw material for a fertilizer using a molten salt after chemical strengthening treatment by ion exchange according to the present embodiment.

[0015] The ion exchange treatment in the present invention is a treatment in which sodium ions (or lithium ions) on the glass surface are exchanged with potassium ions (or sodium ions) in the molten salt, thereby forming a high-density compressive stress layer on the glass surface.

[0016] The ion exchange treatment in the present invention is preferably carried out before a printed layer or coating film is formed on the surface of the glass to be treated. In other words, the glass to be treated with the ion exchange treatment preferably does not have a printed layer and / or coating film. If the glass has a printed layer or coating film, components contained in the printed layer or coating film may be eluted into the molten salt during the ion exchange treatment. If these components are contained in the fertilizer raw material, they may inhibit plant growth. By carrying out the ion exchange treatment in the present invention before forming a printed layer or coating film on the glass surface, the molten salt obtained after the ion exchange treatment in the present invention does not contain components in the printed layer or coating film that inhibit plant growth. This makes it possible to create a fertilizer raw material that does not inhibit plant growth from the molten salt after the ion exchange treatment.

[0017] The molten salt used in the ion exchange treatment in the present invention contains potassium nitrate, because the melting point of the molten salt containing potassium nitrate is below the strain point of the glass and the molten state is maintained.

[0018] The molten salt preferably further contains one or more salts selected from the group consisting of potassium carbonate, sodium carbonate, potassium bicarbonate, sodium bicarbonate, potassium phosphate, sodium phosphate, sodium nitrate, potassium hydroxide, and sodium hydroxide, and particularly preferably contains one or more salts selected from the group consisting of potassium carbonate, sodium carbonate, potassium bicarbonate, and sodium bicarbonate.

[0019] The molten salt used in the ion exchange treatment may contain other chemical species to the extent that the effects of the present invention are not impaired. Examples include alkali chlorides and alkali borates such as sodium chloride, potassium chloride, sodium borate, and potassium borate. These may be added alone or in combination. The molten salt used in the ion exchange treatment preferably does not contain printing ink. If printing ink is contained in the molten salt, the ion exchange treatment may not be carried out properly.

[0020] The molten salt used in the ion exchange treatment can be produced by a known method. Here, repeated ion exchange treatment increases the amount of sodium nitrate contained in the molten salt, and the glass may not obtain the desired surface compressive stress. If the molten salt contains 1000 ppm or more of sodium after the ion exchange treatment, the glass may not obtain the desired surface compressive stress even after the ion exchange treatment, and salt exchange may be necessary. Furthermore, if the molten salt contains 15000 ppm or more of sodium, precipitates may form during the ion exchange treatment, making it impossible to properly perform the ion exchange treatment. Therefore, it is preferable to replace a molten salt containing 1000 ppm to 15000 ppm of sodium with a molten salt having a lower sodium content. Furthermore, it is more preferable to replace a molten salt containing 3000 ppm to 15000 ppm of sodium with a molten salt having a lower sodium content.

[0021] As described above, repeated ion exchange treatments can increase the sodium nitrate content in the molten salt, which can prevent the glass from achieving the desired surface compressive stress. In this case, the molten salt used in the ion exchange treatment is discarded. This discarded molten salt is hereinafter referred to as "waste salt." The waste salt is then solidified by cooling it to a temperature below its melting point, yielding a potassium nitrate-containing salt. The potassium nitrate-containing salt is solid. The compounds contained in the waste salt are the same as the compounds contained in the molten salt used in the ion exchange treatment.

[0022] Cooling can be performed using known methods such as natural cooling (standing), water cooling, and ice cooling. When using these cooling methods, the waste salt may be cooled in the strengthening tank in which ion exchange was performed or in another container transferred from the strengthening tank. Alternatively, the waste salt may be further cooled by transferring it from the strengthening tank to another container during cooling. Furthermore, cooling may be performed by installing a cooling device such as a spot cooler or heater in the strengthening tank or the container. Alternatively, a melt granulation method may be used in which the waste salt heated to a temperature above its melting point is formed into droplets using a nozzle or the like, then cooled and solidified into granules. Specific examples include drum flake granulation, steel belt granulation, and prilling tower granulation. The waste salt may also be cooled and solidified by spraying it into the atmosphere.

[0023] The following describes the case where waste salt is cooled in a container. When the waste salt is cooled and solidified, the temperature inside the container holding the waste salt may vary depending on the location inside the container. In addition, waste salt is a mixture of multiple compounds, and each compound has a different melting point. Therefore, if the temperature during cooling varies depending on the location, the composition distribution of the waste salt inside the container will become uneven. Therefore, it is preferable to cool the waste salt while preventing large temperature differences inside the container. Specifically, for example, the cooling and solidification of the waste salt may be carried out in a container, as shown in Figures 2 and 3.

[0024] Here, an arbitrary point on the bottom surface of the container is defined as the origin, and the straight line from the origin in the depth direction of the container, which is in the positive direction from the bottom surface of the container toward the liquid surface, is defined as the z-axis. For example, in FIG. 2, the direction perpendicular to the bottom surface 4 is defined as the depth direction. Also, the plane perpendicular to the z-axis is defined as the xy plane, and the x-axis and y-axis are perpendicular to each other. For example, in the cases of FIGS. 2 and 3, the origin is defined as O, the bottom surface 4 of the container is defined as the xy plane, and the depth direction of the container 10 is defined as the z-axis. Also, each of FIGS. 2 and 3 illustrates the respective axes and origins.

[0025] During the cooling and solidification, it is preferable to measure the temperature difference of the waste salt at any six points of the container 10 with different x-, y-, and z-coordinate values ​​at a single point where the temperature of point T (the region of the waste salt in contact with the inner wall of the container at a depth midway between the bottom of the container and the liquid surface of the waste salt) shown in FIG. 2 is 345°C or higher and 355°C or lower (for example, points Q, R, S, T, U, and V shown in FIG. 2). The temperature difference range of the waste salt 30 at two of the six points Q to V is preferably within a maximum of 120°C, more preferably within a maximum of 100°C, more preferably within a maximum of 90°C, more preferably within a maximum of 70°C, more preferably within a maximum of 30°C, more preferably within a maximum of 10°C, more preferably within a maximum of 5°C, and most preferably zero. Suppressing the temperature difference within the container during the cooling and solidification has the effect of uniformly distributing the concentrations of water-soluble potassium and nitrate nitrogen in the resulting potassium nitrate-containing salt. Note that the temperature at point T when performing the above measurement is preferably 330°C or higher, because potassium nitrate present in the waste salt solidifies if the temperature is below 330°C. Furthermore, because the temperature at which waste salt is used in a molten state is generally 450°C, the temperature is preferably 330°C or higher and 450°C or lower. Furthermore, if the temperature at point T is 345°C or higher and 355°C or lower, some of the salts contained in the waste salt do not solidify and precipitate, making it easier to verify the variation in composition during cooling and solidification. Therefore, it is most preferable to set the temperature at point T to any one of 345°C or higher and 355°C or lower.

[0026] The temperature at which the waste salt is cooled and solidified is likely to vary at different depths in the container. Furthermore, even at the same depth, the temperature at which the waste salt is cooled is likely to vary at different cross-sectional locations at a given depth (e.g., the center region of the container and the region adjacent to the inner wall of the container). Therefore, the locations at which the waste salt 30 is collected and the temperature measured are preferably any six locations within the container 10 where the waste salt 30 is present. These six locations refer to six locations at different depths or cross-sectional locations at a given depth, i.e., six locations with different z coordinates or x and y coordinates. For the above reasons, it is preferable to collect and measure salt at these six locations. For example, in Figures 2 and 3, d is defined as the distance between the liquid surface 3 of the waste salt 30 and the plane of the bottom surface 4 of the container 10. Point Q is selected from the central region of the xy plane (i.e., the bottom surface 4 of the container 10) at z = zero, and point R is selected from the region of the xy plane adjacent to the inner wall of the container at z = zero. Also, point S is selected from the central region in the xy plane at z = d / 2 (i.e., a plane at an intermediate depth between the liquid surface 3 of the waste salt 30 present in the container 10 and the bottom surface 4 of the container 10), and point T is selected from the region in contact with the inner wall surface in the xy plane at z = d / 2. Furthermore, point U is selected from the central region in the xy plane at z = d (i.e., the liquid surface 3 of the waste salt 30 present in the container 10), and point V is selected from the region in contact with the inner wall surface in the xy plane at z = d (i.e., the liquid surface 3 of the waste salt 30 present in the container 10). It is more preferable to perform measurements at a total of six points, namely points Q, R, S, T, U, and V, selected as above.

[0027] Furthermore, when the cooling rate of the waste salt is high, it is highly likely that the variation in temperature distribution can be suppressed. When the temperature of the waste salt is in the range of 20°C or higher and 450°C or lower, the cooling rate is preferably 3°C / min or higher, more preferably 200°C / min or higher, and most preferably 400°C / min or higher.

[0028] Furthermore, when the volume of the container to be cooled is small, it is highly possible to suppress the variation in the temperature distribution of the waste salt in the container. ３ Preferably, it is 1,000,000 cm or less. ３More preferably, it is 10,000 cm or less. ３ More preferably, it is 5000 cm or less. ３ It is highly preferred that the value is 1000 cm or less. ３ Most preferably, the following:

[0029] Preferably, the difference in nitrate nitrogen concentration (hereinafter referred to as the nitrate nitrogen concentration difference) between 100 g of potassium nitrate-containing salt present in the central region of a cross section parallel to the bottom of the cooled and solidified container at a depth midway between the bottom of the container and the surface of the potassium nitrate-containing salt and the 100 g of potassium nitrate-containing salt present in the central region of the surface of the potassium nitrate-containing salt contained in the container is 1.9 wt% or less, and the difference in water-soluble potassium concentration (hereinafter referred to as the water-soluble potassium concentration difference) is 6.0 wt% or less. This is because, if the concentration difference is within this range, the contents of water-soluble potassium and nitrate nitrogen contained in 1 kg of fertilizer raw material obtained in a lump form after cooling and solidifying and pulverizing the potassium nitrate-containing salt will be stable. Furthermore, in this case, regardless of the cooling location, regardless of which production lot of fertilizer raw material is used to produce the fertilizer, there will be little variation in the amounts of components necessary for plant growth contained in the fertilizer, and it is thought that differences in plant growth efficacy will be less likely to occur. The difference in nitrate nitrogen concentration is more preferably 1.8 wt% or less, even more preferably 1.6 wt% or less, very preferably 1.4 wt% or less, and most preferably 0.10 wt% or less. The difference in water-soluble potassium concentration is more preferably 5.0 wt% or less, even more preferably 3.0 wt% or less, very preferably 1.5 wt% or less, and most preferably 0.25 wt% or less. Here, the nitrate nitrogen referred to in the present invention refers to water-soluble nitric acid (NO ３) and is contained in salts such as potassium nitrate, sodium nitrite, and the like. Nitrate nitrogen is the total content of nitrate nitrogen in the salt expressed in nitrogen (N) equivalent. From the viewpoint of plant growth efficacy, the potassium nitrate-containing salt obtained by the cooling and solidifying process preferably contains 11 wt% or more of nitrate nitrogen, more preferably 11.2 wt%, more preferably 11.4 wt% or more, even more preferably 12 wt% or more, even more preferably 13 wt% or more, and most preferably 15 wt% or more. Furthermore, water-soluble potassium as referred to in the present invention refers to potassium present in the form of water-soluble potassium (K), and exists as salts such as potassium nitrate, potassium carbonate, potassium chloride, and the like. Water-soluble potassium is the total potassium content in the salt expressed in terms of potassium oxide (K). ２ The potassium nitrate-containing salt obtained by the cooling and solidifying process preferably contains 40 wt % or more of water-soluble potassium, more preferably 41 wt % or more, even more preferably 43 wt % or more, still more preferably 45 wt % or more, and most preferably 50 wt % or more, from the viewpoint of plant growth efficacy.

[0030] After cooling and solidification, a solid potassium nitrate-containing salt is obtained. To facilitate dissolution of the fertilizer raw material in a solvent during fertilizer production, the potassium nitrate-containing salt is converted into a lump shape to produce the fertilizer raw material. Possible methods for producing the lump fertilizer raw material include placing the waste salt in a large container, cooling it, and then crushing it after solidification; placing a partition inside the container while cooling and solidifying the waste salt; placing the waste salt in a small container or mold in advance and cooling and solidifying it; spraying the waste salt into the atmosphere to instantly cool it; spraying the waste salt into a cooling tower and cooling and solidifying the waste salt by contact with cold air as it falls; applying the waste salt to the surface of a rotating drum and cooling and solidifying it; and dropping the waste salt onto the surface of a horizontally moving steel belt to cool and solidify it. There are no particular limitations on the method for producing the lump fertilizer raw material, as long as the fertilizer raw material is in a lump size.

[0031] Pulverization is broadly classified into pressure pulverization, impact pulverization, shear pulverization, and attrition pulverization. Examples of pulverizing machines include chain crushers, biaxial roller crushers, and cage mills. When pulverizing the potassium nitrate-containing salt obtained by cooling and solidifying using a large container, the pulverization is preferably carried out by a manual pulverization method using a hammer or drill, or by a known pulverization method using a conventional pulverization device such as a ball mill.

[0032] The lump-shaped fertilizer raw material obtained by crushing has a volume of 10,000 cm per lump. ３ It is preferable to grind the powder to a density of 5000 cm or less. ３ It is more preferable to grind the mixture to a density of 2000 cm or less. ３ It is more preferable to grind the mixture to a depth of 500 cm or less. ３ It is preferable to grind the mixture to a temperature of 250 cm or less. ３ More preferably, it is 125 cm or less. ３ It is most preferable that the volume per lump is less than 1 cm. This is because by reducing the volume per lump, the dissolution time when dissolving the fertilizer raw materials during fertilizer production can be made more efficient and the fertilizer production rate can be increased. There is no particular restriction on the lower limit of the volume per lump, but it is, for example, 1 cm. ３ More than 5 cm is preferable. ３ The above is more preferable.

[0033] When the fertilizer raw material obtained by grinding is powdered, dust flies during grinding. Considering the safety of the grinding operator, it is preferable that dust does not fly. Therefore, when the fertilizer raw material is sieved through a 5.6 mm mesh sieve conforming to JIS Z8801-1, the amount of material passing through the sieve is preferably 1 wt% or less of the input amount, more preferably 0.5 wt% or less, and most preferably 0.1 wt% or less. Furthermore, when sieving a lump of fertilizer raw material through an 11.2 mm mesh sieve conforming to JIS Z8801-1, if the amount of material passing through the sieve is 10% or more of the input amount, the Fire Service Act may limit the amount of fertilizer raw material containing potassium nitrate that can be stored to a minimum of 50 kg. This may increase the number of transportation times and increase transportation costs. Therefore, when the fertilizer raw material is sieved through a 11.2 mm mesh sieve conforming to JIS Z8801-1, the amount of material passing through the sieve is preferably less than 10 wt% of the input amount, more preferably 5 wt% or less, and most preferably 1 wt% or less. Furthermore, when the fertilizer raw material is sieved through a 11.2 mm mesh sieve conforming to JIS Z8801-1, the clumped residue remaining on the sieve is not treated as a hazardous material under the Fire Service Act, but is treated as an ordinary material. Therefore, if each clump of the fertilizer raw material is a granular product with a size of 11.2 mm or more, it can be handled as usual. Therefore, when the fertilizer raw material is sieved through a 11.2 mm mesh sieve conforming to JIS Z8801-1, the amount of material passing through the sieve is most preferably 1 wt% or less of the input amount. Here, the dissolution time of the fertilizer raw material obtained by pulverization does not change depending on the shape, so the lumps of the fertilizer raw material after pulverization may be any lumpy shape, such as a spherical shape, a rectangular parallelepiped shape, a cylindrical shape, a diamond shape, an elliptical shape, or a spiral shape.

[0034] There may be a transportation step in which the fertilizer manufacturer transports the fertilizer raw material obtained by the above-mentioned pulverization. The transportation method used in the transportation step may be a known method using a vehicle such as a truck or an automobile.

[0035] <Method for Producing Liquid Fertilizer Raw Material> When fertilizer raw material is sieved through a 11.2 mm mesh sieve conforming to JIS Z8801-1, the material that passes through the sieve is treated as a hazardous material under the Fire Service Act. Therefore, there is a possibility that all of the fertilizer raw material obtained by grinding cannot be transported. However, even granular fertilizer raw material with a maximum diameter of 11.2 mm or less per lump can be transported if it is soaked in water to produce liquid fertilizer raw material. Therefore, it is preferable to produce a liquid fertilizer raw material by a method that includes soaking the material that passes through the sieve when the above-mentioned fertilizer raw material is sieved through a 11.2 mm mesh sieve conforming to JIS Z8801-1 in water. The soaking of the material in water may be carried out at room temperature using any known method. Furthermore, a portion of the material may be dissolved in water.

[0036] When the mass of water relative to the mass of the permeated material is 10% or less, the permeated material will not be fully immersed in water, and will be treated as a hazardous material under the Fire Service Act. Therefore, it may not be possible to transport all of the fertilizer raw material obtained by grinding. Furthermore, if the mass of water relative to the mass of the permeated material is 80% or more, excess water for soaking the permeated material will have to be transported, which may increase transportation costs. Therefore, the mass of water relative to the mass of the permeated material is preferably 10% to 80%; more preferably 12% to 70%; even more preferably 15% to 60%; and most preferably 20% to 50%.

[0037] <Fertilizer raw material> The fertilizer raw material in the present invention is a fertilizer raw material consisting of a plurality of lumps. The fertilizer raw material is in the form of a lump containing 11 wt % or more of nitrate nitrogen and 40 wt % or more of water-soluble potassium. When two lumps, each having a mass of 50 g to 150 g, are collected per 10 kg of the fertilizer raw material, the difference in water-soluble potassium concentration between the two lumps is 6.0 wt % or less and the difference in nitrate nitrogen concentration is 1.9 wt % or less.

[0038] Here, the nitrate nitrogen referred to in the present invention is water-soluble nitric acid (NO ３) and is contained in salts such as potassium nitrate, sodium nitrate, sodium nitrite, etc. Nitrate nitrogen is the total content of nitrate nitrogen in potassium nitrate-containing salts expressed in nitrogen (N) equivalent. From the viewpoint of plant growth efficacy, the nitrate nitrogen contained in the fertilizer raw material used in the present invention is preferably 11 wt% or more, more preferably 11.2 wt% or more, more preferably 11.4 wt% or more, even more preferably 12 wt% or more, even more preferably 13 wt% or more, and most preferably 15 wt% or more. Furthermore, water-soluble potassium referred to in the present invention refers to potassium present in the form of water-soluble potassium (K), and is present as a salt such as potassium nitrate, potassium carbonate, potassium chloride, etc. Water-soluble potassium is defined as the total potassium content in the salts expressed as potassium oxide (K). ２The water-soluble potassium content is expressed in terms of 0.0 wt %. From the viewpoint of plant growth efficacy, the water-soluble potassium contained in the fertilizer raw material used in the present invention is preferably 40 wt % or more, more preferably 41 wt % or more, more preferably 43 wt % or more, even more preferably 45 wt % or more, and most preferably 50 wt % or more. Furthermore, when two lumps of fertilizer raw material, each having a mass of 50 g to 150 g, are collected per 10 kg of the fertilizer raw material in the present invention, the difference in water-soluble potassium concentration between the two lumps (hereinafter referred to as the water-soluble potassium concentration difference) is preferably 6.0 wt % or less, and the difference in nitrate nitrogen concentration (hereinafter referred to as the nitrate nitrogen concentration difference) is preferably 1.9 wt % or less. If the concentration difference is within this range, the contents of water-soluble potassium and nitrate nitrogen contained per 10 kg of the fertilizer raw material obtained as a powder after cooling and solidifying the potassium nitrate-containing salt will be stable. Furthermore, the difference in nitrate nitrogen concentration is more preferably 1.8 wt% or less, even more preferably 1.6 wt% or less, very preferably 1.4 wt% or less, and most preferably 0.10 wt% or less. The difference in water-soluble potassium concentration is more preferably 5.0 wt% or less, even more preferably 3.0 wt% or less, very preferably 1.5 wt% or less, and most preferably 0.25 wt% or less. Note that "collecting two lumps of fertilizer raw material, each having a mass of 50 g or more and 150 g or less, per 10 kg of fertilizer raw material" means preparing 10 kg of fertilizer raw material as a population and randomly collecting two lumps having a mass of 50 g or more and 150 g or less from that population.

[0039] If a large amount of the fertilizer raw material obtained by grinding is powdered, dust will fly during the grinding operation, increasing the danger to workers during grinding. Therefore, to ensure worker safety, when the fertilizer raw material is sieved through a 5.6 mm mesh sieve conforming to JIS Z8801-1, the amount of material that passes through the sieve is preferably 1 wt% or less of the input amount, more preferably 0.5 wt% or less, and most preferably 0.1 wt% or less. Furthermore, if the amount of material that passes through the sieve when the fertilizer raw material is sieved through an 11.2 mm mesh sieve conforming to JIS Z8801-1 is 10% or more of the input amount, the Fire Service Act may limit the amount of fertilizer raw material containing potassium nitrate that can be stored to a minimum of 50 kg. In this case, the number of transportation times may increase, which may increase transportation costs. Therefore, when the fertilizer raw material is sieved through a 11.2 mm mesh sieve conforming to JIS Z8801-1, the amount of material passing through the sieve is preferably less than 10 wt% of the input amount, more preferably 5 wt% or less, and most preferably 1 wt% or less. Furthermore, when the fertilizer raw material is sieved through a 11.2 mm mesh sieve conforming to JIS Z8801-1, the clumped residue remaining on the sieve is not treated as a hazardous material under the Fire Service Act, but is treated as an ordinary material. Therefore, when a single clump of the fertilizer raw material is a granular product with a size of 11.2 mm or more, it can be handled as usual. Therefore, when the fertilizer raw material is sieved through a 11.2 mm mesh sieve conforming to JIS Z8801-1, the amount of material passing through the sieve is most preferably 1 wt% of the input amount. Here, the dissolution time of the fertilizer raw material does not change depending on the shape, so the lumps of the fertilizer raw material after crushing may be spherical, cubic, cylindrical, diamond-shaped, spiral, or other lumpy shapes.

[0040] In addition, when dissolving raw materials for fertilizer during fertilizer production, in order to improve the efficiency of dissolving time and increase the fertilizer production speed, the raw materials for fertilizer obtained by pulverization are pulverized into lumps with a volume of 10,000 cm3 per lump. ３ It is preferable to grind the powder to a density of 5000 cm or less. ３ It is more preferable to grind the mixture to a density of 2000 cm or less. ３ It is more preferable to grind the mixture to a depth of 500 cm or less. ３ It is preferable to grind the mixture to a temperature of 250 cm or less. ３More preferably, it is 125 cm or less. ３ The lower limit of the volume per lump is not particularly limited, but for example, it is 1 cm ３ More than 5 cm is preferable. ３ The above is more preferable.

[0041] The fertilizer raw material of the present invention can also be used as a raw material for liquid fertilizers and solid fertilizers. The resulting liquid fertilizer can be advantageously applied to a variety of agricultural crops. It has been discovered that optional components such as sodium, calcium, magnesium, and silicon in the fertilizer raw material described in the present invention have several agricultural advantages. For example, trace amounts of sodium contained in the fertilizer raw material obtained according to embodiments of the present invention have the properties of assisting the synthesis of sugars necessary for plant growth and preventing moisture loss in the soil. To this end, the sodium concentration in the fertilizer raw material is preferably 1,000 ppm to 20,000 ppm, more preferably 2,000 ppm to 20,000 ppm, and most preferably 3,000 ppm to 20,000 ppm. The sodium concentration in the fertilizer raw material is measured using atomic absorption spectrometry. Furthermore, calcium in the fertilizer raw material has the properties of promoting plant root growth and neutralizing excess waste products produced within the plant body. Therefore, the calcium concentration in fertilizer raw materials is preferably 1 ppm to 100 ppm, and more preferably 5 ppm to 80 ppm. Furthermore, magnesium in fertilizer raw materials has the property of promoting the movement of phosphate necessary for plant growth and promoting the synthesis of fats and oils stored in seeds such as soybeans. Therefore, the magnesium concentration in fertilizer raw materials is preferably 1 ppm to 100 ppm, and more preferably 5 ppm to 80 ppm. Furthermore, silicon in fertilizer raw materials has the effect of making plants more resistant to pests and diseases and less likely to collapse when ingested by plants. Therefore, the silicon content in fertilizer raw materials is preferably 1 ppm to 10 ppm. The calcium concentration in fertilizer raw materials is measured using atomic absorption spectrometry. The magnesium concentration in fertilizer raw materials is measured using atomic absorption spectrometry. The silicon concentration in fertilizer raw materials is measured using inductively coupled plasma atomic emission spectroscopy (ICP-AES). The fertilizer raw material preferably contains an added potassium salt or sodium salt. The fertilizer raw material obtained by the present invention contains potassium nitrate. The fertilizer raw material may also contain other salts necessary for chemical strengthening treatment, such as calcium carbonate.

[0042] <Liquid Fertilizer Raw Material> When fertilizer raw material is sieved through a sieve with 11.2 mm mesh size conforming to JIS Z8801-1, the material that passes through the sieve is treated as a hazardous material under the Fire Service Act. Therefore, there is a possibility that all of the fertilizer raw material obtained by crushing cannot be transported. However, even granular fertilizer raw material with a maximum diameter of 11.2 mm or less per lump can be transported if it is immersed in water to form a liquid fertilizer raw material. Therefore, the liquid fertilizer raw material of the present invention preferably contains the material that passes through the sieve when sieved through a sieve with 11.2 mm mesh size conforming to JIS Z8801-1, and water. Here, the maximum diameter of the fertilizer raw material is the length of the longest line segment connecting two different points on the outline of the fertilizer raw material in a projection view.

[0043] In liquid fertilizer raw materials, if the mass of water relative to the mass of the permeated material is 10% or less, the permeated material will not be fully immersed in water and will be treated as a hazardous material under the Fire Service Act. Therefore, it may not be possible to transport all of the fertilizer raw material obtained by grinding. Furthermore, if the mass of water relative to the mass of the permeated material is 80% or more, extra water for soaking the permeated material will have to be transported, which may increase transportation costs. Therefore, in liquid fertilizer raw materials, the mass of water relative to the mass of the permeated material is preferably 10% to 80%; more preferably 12% to 70%; even more preferably 15% to 60%; and most preferably 20% to 50%.

[0044] <Method for Producing Fertilizer> The fertilizer raw material of the present invention can be used as a raw material for a liquid fertilizer or a solid fertilizer. Known methods can be used for producing the fertilizer. For example, the method for producing a liquid fertilizer is not particularly limited as long as it can be produced by mixing the fertilizer raw material and, if necessary, a special substance not contained in the fertilizer raw material to form an aqueous solution. Here, the special compound refers to a substance composed of various compounds containing inorganic components such as nitrogen in the form of urea nitrogen or ammonia nitrogen, iron, zinc, manganese, copper, selenium, nickel, molybdenum, or boron. The fertilizer can be easily produced at room temperature without being restricted by temperature or pH during production. Typically, the fertilizer is produced by adding and mixing the fertilizer raw material and, if necessary, the special substance to water in any order. Examples of water used for production include, but are not limited to, tap water, purified water, ion-exchanged water, and distilled water. Dissolution can be performed at room temperature using a known means such as a stirrer, and may be heated to promote dissolution if desired. Filtration may also be performed if necessary.

[0045] The present invention will be described in detail below with reference to examples. However, the examples should not be construed as limiting the scope of the present invention, and the claims are essentially useful for defining the present invention.

[0046] <Waste Salt and Potassium Nitrate-Containing Salt> In this example, 4,500 kg of potassium nitrate-containing salt was produced with the composition shown below. The composition of the molten salt before ion exchange treatment used in this example was 88.3 wt% potassium nitrate, 10.6 wt% potassium carbonate, and 1.1 wt% sodium nitrate, as shown in Table 1 below, and potassium nitrate-containing salt was produced from this molten salt. The sodium concentration of this molten salt was 3,000 ppm. The concentrations of potassium nitrate, sodium nitrate, and potassium carbonate listed in Table 1 are expressed in wt%. The sodium concentration is expressed in ppm.

[0047]

[0048] Examples will be described below, where Examples 1, 2, 3, 4, 5, 6, 7, 8, and 9 are examples.

[0049] Example 1: Glass was immersed in molten salt with the composition shown in Table 1 before ion exchange treatment and subjected to ion exchange treatment. The chemical tempering temperature was 450°C and the chemical tempering time was 35 minutes. The molten salt used here was used for ion exchange treatment multiple times while replacing the glass. The ion exchange treatment was then performed multiple times. When the sodium concentration of the molten salt reached 7000 ppm, the ion exchange chemical tempering treatment was stopped and the cooling and solidification treatment was initiated. Before this cooling and solidification treatment, post-ion exchange waste salt 30 was obtained. The waste salt 30 present at point S in Figure 2 was collected and cooled using a stainless steel round pipe 40, which is a straw-shaped metal rod. The potassium nitrate-containing salt obtained by solidifying the waste salt 30 was analyzed for its composition. The composition of the waste salt 30 was 86.8 wt% potassium nitrate, 10.6 wt% potassium carbonate, and 2.6 wt% sodium nitrate, as shown in Table 1.

[0050] Next, the waste salt 30, which had a sodium concentration of 7000 ppm after the ion exchange treatment, was removed from the chemical strengthening tank and placed in a container measuring 112 cm, 110 cm, and 82 cm in length and 1010240 cm in length. ３The salt was transferred to a rectangular parallelepiped iron container 10 and cooled in the air. During the cooling, the temperature was measured at six locations using a thermocouple thermometer 20. In this example, as shown in FIG. 3 , the six locations were: point U at the center of the xy plane at z = d (i.e., the liquid surface 3 of the waste salt 30 present in the container 10); point V in a region in contact with the inner wall surface of the container in the xy plane at z = d; point S at the center of the xy plane at z = d / 2 (i.e., a plane at a depth intermediate between the liquid surface 3 of the waste salt 30 present in the container 10 and the bottom surface 4 of the container 10); point T in a region in contact with the inner wall surface of the container in the xy plane at z = d / 2; point Q at the center of the xy plane at z = zero (i.e., the bottom surface 4 of the container 10); and point R in a region in contact with the inner wall surface of the container in the xy plane at z = zero (i.e., the bottom surface 4 of the container 10). When the temperature of point T reached 350°C during cooling and solidification, the temperatures of six points, namely points Q, R, S, T, U, and V, were measured using a thermocouple thermometer 20, and the maximum temperature difference between the six points was 20°C. The waste salt 30 present at the two points showing a temperature difference of 20°C was collected and cooled using a stainless steel round pipe 40, which is a straw-shaped metal rod, to obtain a potassium nitrate-containing salt. Thereafter, the concentrations of water-soluble potassium and nitrate nitrogen in the potassium nitrate-containing salt obtained from the two points were measured, and the differences were calculated.

[0051] <Evaluation Method> (Measurement of Nitrate Nitrogen Concentration) In this example, the nitrate nitrogen concentration in the waste salt 30 and the fertilizer raw material was measured by a distillation method using Devarda's alloy reagent in accordance with JIS K8653:2018. (Measurement of Water-Soluble Potassium Concentration) In this example, the water-soluble potassium concentration in the waste salt 30 and the potassium nitrate-containing salt was measured by a volumetric method using sodium tetraphenylborate reagent in accordance with JIS K9521:2020. (Temperature Measurement) In this example, the temperature at each point during the cooling and solidification process was measured using a thermocouple thermometer 20 manufactured by Chino Corporation, "CHINO Sheath K Thermocouple (φ1.6 × 500 mm, WXJ 1.5 m, sheath: SUS316, φ1.6 × 500 mm, compensation lead wire: WXJ 1500 mm, end: M3 Y terminal)." (Measurement of Sodium Concentration) In this example, the sodium concentrations in the molten salt, the waste salt, and the potassium nitrate-containing salt were measured using an atomic absorption spectrophotometer "ZA-3300" manufactured by Hitachi High-Technologies Corporation.

[0052] Example 2: The same conditions as in Example 1 were used, except for the following changes. When cooling the waste salt, as shown in FIG. 4 , a spot cooler 50 was installed to cover the top of the flat portion (the liquid surface of the waste salt 30 present in the container 10) in the xy plane at z = d, and a jacket heater 60 was installed in the region in contact with the outer wall surface of the container in the xy plane at z = 0 to d / 2. When the temperature at point T reached 350°C during cooling and solidification, temperatures were measured at six points: points Q, R, S, T, U, and V. The maximum temperature difference between the six points was 30°C. The waste salt present at the two points showing a temperature difference of 30°C was collected and cooled to obtain potassium nitrate-containing salt. The concentrations of water-soluble potassium and nitrate nitrogen in the potassium nitrate-containing salt obtained from the two points were then measured, and the differences were calculated.

[0053] Example 3 An experiment was carried out under the same conditions as in Example 2, except for the following changes. When the temperature at point T during cooling and solidification of the waste salt reached 350°C, temperatures were measured at six points: points Q, R, S, T, U, and V. The maximum temperature difference at each of the six points was 50°C. The waste salt 30 present at the two points showing a temperature difference of 50°C was sampled and cooled to obtain potassium nitrate-containing salt. The concentrations of water-soluble potassium and nitrate nitrogen in the potassium nitrate-containing salt obtained from the two points were then measured, and the differences were calculated.

[0054] Example 4 An experiment was carried out under the same conditions as in Example 2, except for the following changes. When the temperature at point T during cooling and solidification of the waste salt reached 350°C, temperatures were measured at six points: points Q, R, S, T, U, and V. The maximum temperature difference at each of the six points was 70°C. The waste salt 30 present at the two points showing a temperature difference of 70°C was sampled and cooled to obtain potassium nitrate-containing salt. The concentrations of water-soluble potassium and nitrate nitrogen in the potassium nitrate-containing salt obtained from the two points were then measured, and the differences were calculated.

[0055] Example 5 An experiment was carried out under the same conditions as in Example 2, except for the following changes. When the temperature at point T during cooling and solidification of the waste salt reached 350°C, temperatures were measured at six points: points Q, R, S, T, U, and V. The maximum temperature difference at each of the six points was 90°C. The waste salt 30 present at the two points showing a temperature difference of 90°C was sampled and cooled to obtain potassium nitrate-containing salt. The concentrations of water-soluble potassium and nitrate nitrogen in the potassium nitrate-containing salt obtained from the two points were then measured, and the differences were calculated.

[0056] Example 6 was carried out under the same conditions as Example 2, with the following changes. Glass was immersed in a pre-ion-exchange molten salt with the composition listed in Table 2, and ion exchange treatment was performed. The chemical tempering temperature was 450°C, and the chemical tempering time was 35 minutes. The molten salt used here was used for multiple ion exchange treatments, with the glass being replaced. The ion exchange treatment was performed multiple times, and when the sodium concentration of the molten salt reached 3,300 ppm, the ion-exchange chemical tempering treatment was stopped and the cooling and solidification treatment was initiated. Before this cooling and solidification treatment, post-ion-exchange waste salt 30 was obtained. The waste salt 30 present at point S in Figure 4 was collected and cooled using a stainless steel round pipe 40, which is a straw-shaped metal rod. The potassium nitrate-containing salt obtained was solidified and its composition was analyzed. The composition of the waste salt 30 was 88.2 wt% potassium nitrate, 10.6 wt% potassium carbonate, and 1.2 wt% sodium nitrate, as listed in Table 2. Next, the waste salt 30, which had a sodium concentration of 3,300 ppm after the ion exchange treatment, was removed from the chemical strengthening tank and placed in a container measuring 100 cm, 100 cm, and 55 cm on three sides and 550,000 cm in size. ３ The salt was transferred to a rectangular parallelepiped iron container 10 and cooled in the atmosphere. When the temperature at point T reached 350°C during cooling and solidification, the temperatures were measured at six points: points Q, R, S, T, U, and V. The maximum temperature difference between the six points was 25°C. The waste salt 30 present at the two points showing a temperature difference of 25°C was collected and cooled to obtain a potassium nitrate-containing salt. The concentrations of water-soluble potassium and nitrate nitrogen in the potassium nitrate-containing salt obtained from the two points were then measured, and the differences were calculated.

[0057]

[0058] Example 7 was carried out under the same conditions as Example 2, with the following changes. Glass was immersed in a pre-ion-exchange molten salt with the composition listed in Table 3 for ion exchange treatment. The chemical tempering temperature was 450°C, and the chemical tempering time was 35 minutes. The molten salt used here was used for multiple ion exchange treatments, with the glass being replaced. The ion exchange treatment was repeated multiple times. When the sodium concentration of the molten salt reached 5,000 ppm, the ion-exchange chemical tempering treatment was stopped and the cooling and solidification treatment was initiated. Before this cooling and solidification treatment, post-ion-exchange waste salt 30 was obtained. The waste salt 30 present at point S in Figure 4 was collected and cooled using a stainless steel round pipe 40, a straw-shaped metal rod. The potassium nitrate-containing salt solidified from the waste salt 30 was analyzed for its composition. The composition of the waste salt 30 was 87.5 wt% potassium nitrate, 10.7 wt% potassium carbonate, and 1.8 wt% sodium nitrate, as listed in Table 3. Next, the waste salt 30, which had a sodium concentration of 5000 ppm after the ion exchange treatment, was removed from the chemical strengthening tank and placed in a container with three sides of 100 cm, 100 cm, and 45 cm, and a size of 450,000 cm. ３ The waste salt was transferred to a rectangular parallelepiped iron container 10 and cooled in the atmosphere. When the temperature at point T reached 350°C during cooling and solidification of the waste salt, temperatures were measured at six points: points Q, R, S, T, U, and V. The maximum temperature difference between the six points was 92°C. The waste salt 30 present at the two points showing a temperature difference of 92°C was collected and cooled to obtain potassium nitrate-containing salt. The concentrations of water-soluble potassium, nitrate nitrogen, and sodium in the potassium nitrate-containing salt obtained from the two points were then measured, and the differences were calculated.

[0059]

[0060] Example 8 An experiment was carried out under the same conditions as in Example 2, except for the following changes. After the ion exchange treatment, the waste salt 30 having a sodium concentration of 7000 ppm was removed from the chemical strengthening tank and transported to a container having three sides of 100 cm, 100 cm, and 75 cm, and a size of 750,000 cm. ３The waste salt was transferred to a rectangular parallelepiped iron container 10 and cooled in the atmosphere. When the temperature at point T reached 350°C during cooling and solidification of the waste salt, the temperatures were measured at six points: points Q, R, S, T, U, and V. The maximum temperature difference between the six points was 105°C. The waste salt 30 present at the two points showing a temperature difference of 105°C was collected and cooled to obtain potassium nitrate-containing salt. The concentrations of water-soluble potassium, nitrate nitrogen, and sodium in the potassium nitrate-containing salt obtained from the two points were then measured, and the differences were calculated.

[0061] Example 9 An experiment was carried out under the same conditions as in Example 2, except for the following changes. After the ion exchange treatment, the waste salt 30 having a sodium concentration of 7000 ppm was removed from the chemical strengthening tank and transported to a container having three sides of 100 cm, 100 cm, and 65 cm, and a size of 650,000 cm. ３ The waste salt was transferred to a rectangular parallelepiped iron container 10 and cooled in the atmosphere. When the temperature at point T reached 350°C during cooling and solidification of the waste salt, temperatures were measured at six points: points Q, R, S, T, U, and V. The maximum temperature difference between the six points was 115°C. The waste salt 30 present at the two points showing a temperature difference of 115°C was collected and cooled to obtain potassium nitrate-containing salt. The concentrations of water-soluble potassium, nitrate nitrogen, and sodium in the potassium nitrate-containing salt obtained from the two points were then measured, and the differences were calculated.

[0062] Tables 4 and 5 show the concentrations of water-soluble potassium and nitrate nitrogen in each potassium nitrate-containing salt at the two points where the temperature difference was greatest during the cooling and solidification process in each of Examples 1 to 9, as well as the concentration differences of water-soluble potassium, nitrate nitrogen, and sodium in each potassium nitrate-containing salt at the two points where the temperature difference was greatest during the cooling and solidification process. The units of concentration in the tables are wt %, and the units of temperature difference in the tables are ° C.

[0063] As can be seen from Tables 4 and 5, when the maximum temperature difference between two points is within 120°C as in Examples 1 to 9, the bias in the composition distribution of water-soluble potassium, nitrate nitrogen, and sodium can be suppressed, and a fertilizer raw material with excellent quality can be obtained.

[0064]

[0065]

[0066] From the above results, it was found that the fertilizer raw material according to the present invention achieves a uniform distribution of water-soluble potassium and nitrate nitrogen in the resulting potassium nitrate-containing salt by suppressing the temperature difference within the container during cooling and solidification in the production of the fertilizer raw material. This also suppresses the bias in the compositional distribution of water-soluble potassium and nitrate nitrogen in the fertilizer raw material obtained by crushing the potassium nitrate-containing salt, resulting in a high-quality fertilizer raw material. It was also found that this allows almost all of the waste salt 30 that would normally be discarded after chemical strengthening treatment to be reused as a fertilizer raw material. It was also found that there is a corresponding relationship between the temperature difference within the container during cooling and the difference in water-soluble potassium concentration and nitrate nitrogen concentration in the resulting potassium nitrate-containing salt.

[0067] Although the present invention has been described in detail and with reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the invention.

[0068] Although the present invention has been described in detail with reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the present invention. This application is based on a Japanese patent application (Patent Application No. 2024-109696) filed on July 8, 2024, the entirety of which is incorporated by reference.

[0069] According to the present invention, a fertilizer raw material derived from molten salt used in ion exchange treatment can be obtained by subjecting waste salt to cooling and solidifying, and then pulverizing the potassium nitrate-containing salt obtained by cooling and solidifying. Furthermore, a fertilizer derived from chemically strengthened glass molten salt can be obtained by subjecting the molten salt to fertilizer production processes such as transportation, dissolving, heating, and stirring, in addition to the fertilizer raw material production processes of cooling and solidifying and pulverizing the molten salt. This process reduces the amount of waste salt discarded, reduces the environmental load, and makes it possible to reuse almost all of the molten salt used in ion exchange treatment for fertilizer production. It also makes it possible to produce fertilizer raw materials with guaranteed quality.

[0070] 1: Inner wall surface of container containing molten salt 3: Liquid surface of molten salt 4: Bottom surface of container 10: Container 20: Thermocouple thermometer 30: Waste salt 40: Stainless steel round pipe 50: Spot cooler 60: Jacket heater Q: Center of xy plane (bottom surface 4 of container 10) at z = zero R: Area in contact with the inner wall surface of the container in the xy plane (bottom surface 4 of container 10) at z = zero S: Center of xy plane (plane at a depth intermediate between the liquid surface 3 of the waste salt 30 present in the container 10 and the bottom surface 4 of the container 10) at z = d / 2 T: Area in contact with the inner wall surface of the container in the xy plane (plane at a depth intermediate between the liquid surface 3 of the waste salt 30 present in the container 10 and the bottom surface 4 of the container 10) at z = d / 2 U: Center of xy plane (liquid surface 3 of the waste salt 30 present in the container 10) at z = d V: Area in contact with the inner wall surface of the container on the xy plane at z = d (liquid surface 3 of the waste salt 30 present in the container 10)

Claims

1. A method for producing a raw material for a fertilizer, comprising: subjecting glass to ion exchange with a molten salt containing potassium nitrate; and cooling and solidifying the molten salt to obtain a potassium nitrate-containing salt.

2. The method for producing a fertilizer raw material according to claim 1, further comprising crushing the potassium nitrate-containing salt to produce the fertilizer raw material, wherein when the molten salt is cooled and solidified in the container for cooling and solidifying, the molten salt is cooled in the container, and at a depth midway between the bottom of the container and the liquid surface of the molten salt, a temperature of the molten salt in a region in contact with the inner wall surface of the container is 345°C or higher and 355°C or lower, and a temperature difference of the molten salt at any six points in the container is within a maximum range of 120°C.

3. A method for producing a fertilizer raw material as set forth in claim 2, wherein the difference in nitrate nitrogen concentration between 100 g of the potassium nitrate-containing salt present in a central region of a cross section parallel to the bottom surface at a depth midway between the bottom surface of the container and the surface of the potassium nitrate-containing salt is 1.9 wt% or less, and the difference in water-soluble potassium concentration between 100 g of the potassium nitrate-containing salt present in a central region of the surface at the surface is 6.0 wt% or less.

4. The method for producing a fertilizer raw material according to claim 1 or 2, wherein when the fertilizer raw material is sieved through a sieve with 5.6 mm openings conforming to JIS Z8801-1, the amount of material passing through the sieve is 1 wt% or less of the input amount.

5. The method for producing a fertilizer raw material according to claim 1 or 2, wherein when the fertilizer raw material is sieved through a sieve with 11.2 mm openings conforming to JIS Z8801-1, the amount of material passing through the sieve is less than 10 wt% of the input amount.

6. The method for producing a fertilizer raw material according to claim 1 or 2, wherein the proportion of water-soluble potassium relative to the total weight of the potassium nitrate-containing salt is 40 wt% or more, and the proportion of nitrate nitrogen relative to the total weight of the potassium nitrate-containing salt is 11 wt% or more.

7. The method for producing a fertilizer raw material according to claim 1 or 2, wherein the molten salt further contains one or more salts selected from the group consisting of potassium carbonate, sodium carbonate, potassium bicarbonate, sodium bicarbonate, potassium phosphate, sodium phosphate, sodium nitrate, potassium hydroxide, and sodium hydroxide.

8. The fertilizer raw material obtained by the grinding is composed of a plurality of lumps, and the volume of each lump is 10,000 cm ３ The method for producing a fertilizer raw material according to claim 2, wherein:

9. The container has a volume of 2,000,000 cm ３ The method for producing a fertilizer raw material according to claim 2, wherein:

10. A fertilizer raw material consisting of a plurality of lumps, wherein the ratio of water-soluble potassium to the fertilizer raw material is 40 wt% or more, and the ratio of nitrate nitrogen to the total weight of the fertilizer raw material is 11 wt% or more, and when two lumps, each having a mass of 50 g to 150 g, are collected per 10 kg of the fertilizer raw material, the difference in water-soluble potassium concentration between the two lumps is 6.0 wt% or less, and the difference in nitrate nitrogen concentration is 1.9 wt% or less.

11. The fertilizer raw material according to claim 10, wherein when sieved through a 5.6 mm mesh sieve conforming to JIS Z8801-1, the amount passing through the sieve is 1 wt% or less of the input amount.

12. The fertilizer raw material according to claim 10 or 11, wherein when sieved through a sieve with 11.2 mm openings conforming to JIS Z8801-1, the amount passing through the sieve is less than 10 wt% of the input amount.

13. The fertilizer raw material according to claim 10 or 11, wherein the ratio of sodium to the fertilizer raw material is 1,000 ppm or more and 20,000 ppm or less.

14. The fertilizer raw material has a volume of 10,000 cm per lump. ３ The fertilizer raw material according to claim 10 or 11, wherein:

15. A method for producing a fertilizer, comprising producing a fertilizer using the fertilizer raw material according to claim 10 or 11.

16. A method of using potassium nitrate-containing salts obtained after ion exchange of glass as a raw material for fertilizers.

17. A method for producing a liquid fertilizer raw material, comprising sieving the fertilizer raw material according to claim 10 or 11 through a sieve conforming to JIS Z8801-1 and having an opening of 11.2 mm, and immersing the material that passes through the sieve in water.

18. A liquid fertilizer raw material comprising the fertilizer raw material according to claim 10 or 11, which is sieved through a sieve with 11.2 mm openings conforming to JIS Z8801-1, and a material that passes through the sieve, and water.

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