Solid compositions and fertilizers for use as fertilizers

Abstract

To provide a fertilizer manufacturing method capable of obtaining a solid composition at low cost including a fertilizer component recovered from an aqueous solution including a phosphate ion and an ammonium ion.SOLUTION: A fertilizer manufacturing method includes Step 101 of adding combusted ashes to an ammonium phosphate aqueous solution and agitating and mixing the mixture, Step 102 of leaving the mixture to stand, and then Step 103 of obtaining a sediment (solid composition). Accordingly, a fertilizer component can be recovered as a solid material without requiring additional energy related to heating or reaction other than an agitation operation at normal temperature and under ordinary pressure.SELECTED DRAWING: Figure 1

Description

【Technical Field】 【0001】 The present invention relates to a method for producing a fertilizer that recovers fertilizer components from an aqueous solution containing phosphate ions and ammonium ions to obtain a solid composition, a method for recovering fertilizer components from an aqueous solution containing phosphate ions and ammonium ions, and a solid composition obtained by these methods. 【Background Art】 【0002】 Treatment of sewage and waste is carried out, and resources are recovered from sewage and waste and reused. As one such technology, a recovery device for recovering resources (recovering phosphorus using the MAP reaction) from livestock barn sewage is disclosed in Patent Document 1. Further, Patent Document 2 discloses a technology related to recovering phosphorus and ammonia from treated water such as sewage and using them as fertilizers. 【Prior Art Documents】 【Patent Documents】 【0003】 【Patent Document 1】 Japanese Patent Application Laid-Open No. 2004-195453 【Patent Document 2】 Japanese Patent Application Laid-Open No. 2004-0​​​​​​​​​​​In the method of recovering ammonia by passing ammonia gas through a phosphoric acid solution, the resulting recovered solution is an ammonium phosphate solution, which also contains phosphoric acid, making it suitable for use as fertilizer. However, the recovered material obtained by the above method is a liquid containing a large amount of water, and the volume and mass occupied by water are large, and liquid storage containers are required, making it difficult to handle (and costly) in terms of storage and transportation. Thus, because it is not cost-effective, the method of recovering ammonia by contacting ammonia gas generated during the composting process with phosphoric acid, and the use of the recovered liquid obtained by this method, have not become widespread. 【0005】 In view of the above, the present invention aims to provide a method for producing fertilizer that can obtain a solid composition obtained by recovering fertilizer components from an aqueous solution containing phosphate ions and ammonium ions at low cost, a method for recovering fertilizer components, and a solid composition obtained by these methods. [Means for solving the problem] 【0006】 (Composition 1) A method for producing a fertilizer containing a phosphate component, comprising the step of producing a solid composition by mixing an aqueous solution containing phosphate ions and ammonium ions with combustion ash containing at least magnesium. 【0007】 (Configuration 2) The method for producing fertilizer according to configuration 1, wherein the combustion ash is biomass combustion ash. 【0008】 (Composition 3) The method for producing fertilizer according to configuration 2, wherein the biomass combustion ash is livestock manure combustion ash. 【0009】 (Composition 4) The method for producing fertilizer according to configuration 3, wherein the livestock manure combustion ash is chicken manure combustion ash. 【0010】 (Composition 5) The method for producing fertilizer according to configuration 2, wherein the biomass combustion ash is wood ash. 【0011】 (Composition 6) A method for producing a fertilizer containing a phosphate component, comprising the step of producing a solid composition by mixing an aqueous solution containing phosphate ions and ammonium ions with steel slag containing at least magnesium. 【0012】 (Composition 7) A method for producing fertilizer according to any one of configurations 1 to 6, comprising the step of adding the combustion ash or the steel slag to the aqueous solution and stirring. 【0013】 (Composition 8) A method for producing fertilizer according to any one of the components 1 to 7, wherein 5% or more by mass of the combustion ash or the steel slag is added to the aqueous solution. 【0014】 (Composition 9) A method for producing fertilizer according to any one of configurations 1 to 6, comprising the step of spraying the aqueous solution onto the combustion ash or the steel slag. 【0015】 (Composition 10) A method for recovering fertilizer components from an aqueous solution containing phosphate ions and ammonium ions, comprising the step of producing a solid composition containing fertilizer components by mixing the aqueous solution with combustion ash containing at least magnesium. 【0016】 (Composition 11) A method for recovering fertilizer components from an aqueous solution containing phosphate ions and ammonium ions, comprising the step of producing a solid composition containing fertilizer components by mixing the aqueous solution with steel slag containing at least magnesium. 【0017】 (Composition 12) A solid composition mainly composed of inorganic substances, wherein the total of (a) a mixture of a compound of phosphate ions and ammonium ions and a compound of phosphate ions and potassium ions, or a compound of phosphate ions and ammonium ions, (b) a compound of phosphate ions, magnesium ions and ammonium ions, and (c) a compound of phosphate ions and calcium ions is 70% by mass or more. 【Advantages of the Invention】 【0018】 According to the present invention, a solid composition obtained by recovering a fertilizer component from an aqueous solution containing phosphate ions and ammonium ions can be obtained at low cost. 【Brief Description of the Drawings】 【0019】 [Figure 1] A flowchart showing an outline of the steps of a method for producing a fertilizer according to an embodiment of the present invention [Figure 2] A photograph showing a comparison of the solid volume ratios obtained in Example 1 and the comparative example [Figure 3] A graph showing the relationship between the solid volume ratio and the combustion ash addition rate in Example 1 [Figure 4] A diagram showing the analysis results of the reactant obtained in Example 1 [Figure 5] A graph showing the change over time of the solid volume ratio in Example 1 [Figure 6] A photograph showing a comparison of the solid volume ratios obtained in Example 1 and the comparative example [Figure 7] A graph showing the relationship between the solid volume ratio and the combustion ash addition rate in Example 1 [Figure 8] A photograph showing the solid volume ratio obtained in Example 1 [Figure 9] A photograph showing the reactant obtained in Example 1 [Figure 10] A graph showing the relationship between the solid volume ratio and the steel slag addition rate in Example 2 [Figure 11] A photograph showing the solid volume ratio obtained in Example 2 [Figure 12] A photograph showing the solid volume ratio obtained in Example 2 [Figure 13] Photograph showing the reaction product obtained in Example 2 [Modes for carrying out the invention] 【0020】 The embodiments of the present invention will be described in detail below with reference to the drawings. Note that the following embodiments are merely examples of how the present invention can be implemented, and do not limit the present invention to their scope. 【0021】 <Embodiment 1> The method for producing a fertilizer containing a phosphate component according to Embodiment 1 of the present invention includes the step of producing a solid composition by mixing an aqueous solution containing phosphate ions and ammonium ions with combustion ash containing at least magnesium. The method for producing the fertilizer in this embodiment, as shown in Figure 1, consists of a simple process of adding combustion ash to an aqueous solution of ammonium phosphate (hereinafter referred to as "ammonium phosphate solution"), stirring and mixing (step 101), letting it stand (step 102), and obtaining a precipitate (solid composition) (step 103). This allows for the recovery of fertilizer components as a solid material under normal temperature and pressure conditions, without the need for heating or additional energy input for the reaction, other than stirring. As shown in the experimental results below, the recovered material obtained when combustion ash is added to an ammonium phosphate solution is about 2 to 3 times larger in volume than when combustion ash is added to water, and contains a large amount of fertilizer components. 【0022】 A phosphate ammonium solution can be any aqueous solution containing phosphate ions and ammonium ions. As mentioned above, for example, it can be obtained as a recovered liquid by contacting ammonia gas generated during the composting process in livestock facilities with phosphoric acid to recover the ammonia. It can also be produced in other industrial processes. This invention is a technology that can promote the effective utilization of resources contained in such ammonium phosphate solutions. 【0023】 The combustion ash added to the ammonium phosphate solution is "combustion ash containing at least magnesium." The fertilizer manufacturing method of this embodiment utilizes the MAP reaction to precipitate fertilizer components from an ammonium phosphate solution. Combustion ash is used to supply the magnesium necessary for the MAP reaction and to obtain the pH required for the MAP reaction. In other words, it utilizes the magnesium contained in the combustion ash and the alkalinity of the combustion ash. An example of "combustion ash containing at least magnesium" is combustion ash from burning biomass. Specific examples of biomass combustion ash include combustion ash from livestock manure and wood ash. While "combustion ash containing at least magnesium" is not limited to these, they are preferred because they can be obtained at low cost. 【0024】 Regarding step 101 in Figure 1, the addition of combustion ash to the ammonium phosphate solution may be done by any method that allows the two to come into contact. Similarly, stirring and mixing may be done by any method that ensures overall contact between the ammonium phosphate solution and the combustion ash. While stirring and mixing are done to ensure an efficient reaction, they are not necessarily essential. For example, by devising a method for adding the combustion ash to the ammonium phosphate solution (such as a method that allows for efficient contact between the two), a sufficient reaction can be obtained without special stirring. In this embodiment, as a method for bringing the ammonium phosphate solution and combustion ash into overall contact, combustion ash is added to the ammonium phosphate solution and stirred and mixed. However, the present invention is not limited to this, and any method that brings the ammonium phosphate solution and combustion ash into contact may be used. For example, the ammonium phosphate solution may be sprayed onto the combustion ash. 【0025】 Regarding step 102 in Figure 1, the predetermined standing time after contacting the ammonium phosphate solution with the combustion ash is sufficient time for the MAP reaction to proceed. The "predetermined time" can be appropriately determined by experimentally determining the time required for the necessary reaction to occur. In some cases, the "predetermined time" may be extremely short, to the point where standing is not actually performed. Furthermore, it is not always necessary to "settle" the mixture; for example, stirring may be continued while waiting for the required reaction time to elapse. 【0026】 Regarding step 103 in Figure 1, the recovery of the solid composition can be carried out using any method that can recover the solid from the liquid, such as a filtration method. Furthermore, if necessary, the obtained solid composition may be dried. 【0027】 The reaction principle in the fertilizer manufacturing method of this embodiment is similar to the MAP reaction described in Patent Document 1, etc., but the reaction process of this embodiment utilizes the magnesium ions contained in the combustion ash and the high pH of the combustion ash itself. The resulting material contains MAP, which tends to solidify, but maintains a sandy state like the original combustion ash, making it easy to handle afterward. By focusing on combustion ash as a material, this method, which allows for the acquisition of sandy solidified components simply by adding the material without inputting external energy, is extremely useful. This makes it possible to produce solid material containing high concentrations of fertilizer components, minimizing the impact on transportation costs due to the moisture content of the material, which has been a limitation in its use until now. 【0028】 (Example 1) Next, we will describe an example of a method for producing fertilizer by adding combustion ash to an ammonium phosphate solution. The ammonium phosphate solution used in Example 1 was modeled after the solution obtained as a recovered liquid in "Ammonia Recovery from a Closed Vertical Composting System at a Pig Farm and Utilization of the Recovered Liquid" by Yoichiro Kojima, Ryo Nakakubo, Hideki Matsuoka, Takashi Kenjo, Tomotaka Asano, and Mika Ishida, Agricultural Facilities, Vol. 50, No. 2 (2019.06), and contained NH4H2PO4 and (NH4)2HPO4. + and PO4 3- NH4 in molar ratio + :PO4 3- A solution was prepared by mixing the ingredients in a ratio of 1.6:1, resulting in a nitrogen concentration of 6% by mass and a phosphoric acid concentration of 19% by mass. The solution contains 6% by mass of nitrogen and 19% by mass of phosphorus, with a water content of approximately 65% ​​by mass. It meets the standards for ordinary fertilizer and can be used as a raw material for mixed compost and compound fertilizers. However, as mentioned above, the recovered liquid is a liquid containing more than 60% by mass of water, and the costs associated with long-distance transportation are limiting its use, so it is not currently being utilized to its full potential. 【0029】 In Example 1, chicken manure combustion ash and wood ash were used as combustion ash. Although chicken manure ash, obtained by burning chicken manure, is used as a fertilizer raw material to some extent, it is difficult to use on its own and is a low-value, underutilized material that can be obtained cheaply. Wood ash is commonly available as a soil conditioner and fertilizer, and can be obtained easily and inexpensively. 【0030】 Figure 2 shows the ammonium phosphate solution described above after adding chicken manure combustion ash at room temperature (mass ratio of solution to combustion ash = 10:1 (addition rate 10%)), and after shaking and stirring, the solution was allowed to stand for about 1 hour. For comparative examples, solutions were prepared by adding chicken manure combustion ash to water and by adding chicken manure combustion ash to ammonium sulfate solution. All conditions were the same except for the change in solution. As can be seen from Figure 2, when chicken manure combustion ash was added to water, no change in the volume of the precipitate was observed, while when chicken manure combustion ash was mixed with ammonium phosphate solution, a precipitate of about 2 to 3 times the amount obtained when water and ash were mixed was obtained. 【0031】 Figure 3 shows the results when the addition rate of chicken manure combustion ash was varied for both ammonium phosphate solution and water. These results also confirmed that the volume of precipitated solids (solid volume ratio) was almost equal to the addition rate in the case of water, while in the case of ammonium phosphate solution it reached 2 to 3 times the volume ratio. Regarding pH, while the pH of water exceeded 10 even with a 0.1% addition rate, the ammonium phosphate solution maintained the same pH as the undiluted solution even after combustion ash was added, due to its buffering effect (only an increase of about 0.2). As shown in Figure 3, in order to efficiently obtain the solid composition, it is preferable to add 5% or more by mass of combustion ash to the ammonium phosphate solution. 【0032】 The precipitate (solid composition) obtained by adding chicken manure combustion ash to the above ammonium phosphate solution was filtered and dried at 105°C for 24 hours to obtain the reaction product. Figure 4 shows a comparison of the concentrations (mass%) of constituent ions (left) and the chemical formulas and semi-quantitative values ​​(right) of the crystalline phases for the obtained reactants and the chicken manure combustion ash used. The concentrations (mass%) of the constituent ions were measured using infrared combustion for carbon, the Kjeldahl method for nitrogen, and X-ray fluorescence for the others. The reactants clearly have higher concentrations of phosphorus (P) and nitrogen (N) ions than the chicken manure ash used, and are mainly composed of crystalline material containing phosphate ions and ammonium ions. In other words, a solid composition is obtained by recovering fertilizer components from an ammonium phosphate solution. As shown in the table on the right side of Figure 4, the recovered solid composition consists of ammonium dihydrogen phosphate or a mixture of ammonium dihydrogen phosphate and potassium dihydrogen phosphate, magnesium ammonium phosphate (MAP), and calcium phosphate, totaling 80% by mass or more (85% by mass). Preferably, the total of (a) a mixture of a compound of phosphate ions and ammonium ions and a compound of phosphate ions and potassium ions, or a compound of phosphate ions and ammonium ions, (b) a compound of phosphate ions, magnesium ions and ammonium ions, and (c) a compound of phosphate ions and calcium ions is 70% by mass or more, and more preferably 80% by mass or more. The solid composition recovered by the method described above consists mainly of inorganic materials and basically does not contain organic materials (organic materials make up 5% by mass or less). 【0033】 Figures 9(a) and 9(b) are photographs showing the reaction products obtained as described above. As shown in Figure 9, the reaction product obtained by the example is in the form of sand and is easy to handle. The MAP (magnesium ammonium phosphate) obtained by the conventional MAP method crystallizes and adheres to the inside of the reaction vessel, making recovery difficult. https: / / www.naro.affrc.go.jp / project / results / research_digest / digest_technology / digest_animals / 054723.html The aforementioned website discloses a device that includes a wire mesh or similar collection mechanism for attaching MAP, which makes removal from the reaction vessel easy, but requires the additional step of recovering the MAP that has adhered to the wire mesh. In contrast, in this embodiment, the MAP-based components precipitate around the combustion ash, and a sandy solid composition can be obtained without the components adhering to each other. This composition can be easily recovered by filtration or other means, making it extremely useful. Furthermore, conventional methods required mixing magnesium chloride (bittern) as a magnesium source for the MAP reaction, adding caustic soda (sodium hydroxide) to adjust the pH to alkaline, and aeration. However, in this embodiment, only combustion ash needs to be added, which is simple, inexpensive, and extremely useful. 【0034】 Figure 5 is a graph showing the change over time in precipitate percentage (solid volume percentage) for the following solutions: ammonium phosphate solution with added chicken manure ash, water with added chicken manure ash, ammonium phosphate solution with added wood ash, and water with added wood ash. Wood ash is the ash remaining after burning grass and wood. Here, we used wood ash with 0.4% nitrogen ions, 11.3% phosphate ions, 3.8% magnesium ions, and a pH of 12.2. Figure 5 is a graph showing the results when the solution mass was set to 100g and 10% ash was added relative to the solution mass, and Figure 6 is a photograph of the same results. 【0035】 As shown in Figure 5, under the condition of "ammonium phosphate solution + 10% chicken manure combustion ash," the precipitate rate increased to about 75% after 24 hours of ash addition and stirring, and then stabilized, although there were some fluctuations thereafter. Under the condition of "ammonium phosphate solution + 10% wood ash," it took 43.2 hours to stabilize, but after stabilization, a precipitate of a similar magnitude to that under the ammonium phosphate solution + chicken manure combustion ash condition was obtained. On the other hand, no significant volume increase was observed under the condition of adding ash to water. From this, it can be seen that under the condition of "ammonium phosphate solution + 10% chicken manure ash added," a standing time of about one day is sufficient, while for "ammonium phosphate solution + 10% wood ash added," a standing time of slightly less than two days is sufficient. It should be noted that the reaction may be left to stand until it reaches a near equilibrium state, but the present invention is not limited to this. As shown in Figure 5, the volume of the precipitate more than doubles immediately after the ash is added to the solution, so it may be possible to collect it immediately without leaving a standing time (step 102 in Figure 1 is not essential in the present invention). 【0036】 Figure 7 is a graph showing the volume percentage of precipitate when the mass ratio of ash to the solution is 1%, 5%, 10%, 30%, and 50% for each of the following: "ammonium phosphate solution + chicken manure combustion ash," "water + chicken manure combustion ash," "ammonium phosphate solution + wood ash," and "water + wood ash." Figure 8 is a photograph of the same results. Under conditions where chicken manure ash or wood ash was added to the ammonium phosphate solution, the precipitate increased at a volume several times greater than that of water + ash conditions with the same addition rate, depending on the addition rate, and the supernatant almost disappeared at around 30%. The reason why the precipitate rate was higher with wood ash than with chicken manure combustion ash is that the bulk density of wood ash is lower, resulting in a larger volume of added material. 【0037】 As described above, the fertilizer manufacturing method or fertilizer component recovery method described above allows for the simple operation of mixing underutilized materials such as ammonium phosphate solution and chicken manure ash to obtain a solid material containing a large amount of fertilizer components from ammonium phosphate solution. This makes it possible to effectively utilize underutilized materials that have not been fully utilized in the past from an economic standpoint. 【0038】 <Embodiment 2> The method for producing a fertilizer containing a phosphate component according to Embodiment 2 of the present invention comprises the step of producing a solid composition by mixing an aqueous solution containing phosphate ions and ammonium ions with steel slag containing at least magnesium. The method for producing fertilizer containing phosphate components in this embodiment (or method for recovering fertilizer components) differs from Embodiment 1 in that it uses steel slag as an additive material. 【0039】 Steel slag is a by-product generated during the smelting of metals from ore, and is broadly classified into blast furnace slag and converter (steelmaking) slag. While a detailed explanation of steel slag itself is not provided here, blast furnace slag contains fertilizer components such as CaO, SiO2, and MgO, while converter (steelmaking) slag contains these in addition to FeO, MnO, and P2O5, and is therefore used as fertilizer. Furthermore, due to the lime it contains, steel slag becomes alkaline when it reacts with water. 【0040】 The method for producing fertilizer in this embodiment is conceptually the same as that of Embodiment 1, except for the use of steel slag as an additive, including the reaction principle (using the MAP reaction to precipitate fertilizer components from an ammonium phosphate solution, with the additive providing the magnesium necessary for the MAP reaction and obtaining the pH necessary for the MAP reaction) and the manufacturing process (1. addition to the ammonium phosphate solution, 2. stirring, standing, 3. recovery), so a detailed explanation is omitted here. 【0041】 (Example 2) Next, we will describe an example of a method for producing fertilizer by adding steel slag to an ammonium phosphate solution. The ammonium phosphate solution used in Example 2 was prepared by mixing (NH4)2HPO4 and NH4H2PO4 in a molar ratio of 2:1, so that the nitrogen concentration was 6% by mass. 【0042】 In Example 2, calcium silicate fertilizer (which uses granulated slag itself as fertilizer) was used as blast furnace slag. In addition, converter lime fertilizer (which uses converter slag itself as fertilizer) was used as converter (steelmaking) slag. 【0043】 Figure 10 is a graph showing the volume fraction of the precipitate for "ammonium phosphate solution + blast furnace slag addition" and "ammonium phosphate solution + converter slag addition" when the mass ratio of slag to the solution is 1%, 5%, 10%, 30%, 50%, 70%, and 100%, while Figures 11 and 12 are photographs of the same results. Furthermore, as a comparative example, Figure 10 shows the volume fraction of the precipitate when the mass ratio of slag to the solution is 10%, 30%, and 50% for "water + blast furnace slag addition" and "water + converter slag addition". In Figure 10, the graphs for "ammonium phosphate solution + blast furnace slag addition" and "ammonium phosphate solution + converter slag addition" show the conditions under which accurate measurement of precipitate ratios was difficult due to precipitates, etc., indicated by dotted lines. 【0044】 As shown in Figure 10, under conditions where blast furnace slag or converter slag is added to the ammonium phosphate solution, the amount of precipitate increases by several times the volume under conditions with equivalent addition rates of water + blast furnace slag or converter slag. In both cases of blast furnace slag addition and converter slag addition, adding 5% or more to the ammonium phosphate solution clearly increases the amount of precipitate compared to when it is added to water. Therefore, in order to efficiently obtain a solid composition, it is best to add 5% or more of steel slag by mass to the ammonium phosphate solution. 【0045】 Figure 13 is a photograph showing the dried reaction product obtained in Example 2 (where the mass ratio of slag to the solution was 50% for both "ammonium phosphate solution + blast furnace slag addition" and "ammonium phosphate solution + converter slag addition"). As shown in Figure 13, the reaction product obtained in Example 2 is also sandy and easy to handle. The dried product of "ammonium phosphate solution + blast furnace slag addition" is a somewhat hard solid, but it is hard enough to be easily crushed by hand and becomes sandy when crushed. 【0046】 As described above, the fertilizer manufacturing method or fertilizer component recovery method described above allows for the production of a solid material containing a large amount of fertilizer components from an ammonium phosphate solution by simply mixing the ammonium phosphate solution with steel slag. This makes it possible to effectively utilize underutilized materials that have not been fully utilized in the past due to economic considerations and other factors.

Claims

[Claim 1] A solid fertilizer composition mainly composed of inorganic substances, wherein the total amount of (a) ammonium dihydrogen phosphate, or a mixture of ammonium dihydrogen phosphate and potassium dihydrogen phosphate, (b) magnesium ammonium phosphate (MAP), and (c) calcium phosphate is 80% by mass or more.

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