Liquid potassium phosphate fertiliser and method for producing same

Abstract

The present invention relates to a method for producing a liquid potassium phosphate fertiliser. The method for producing a liquid potassium phosphate fertiliser comprises reacting potassium carbonate (K2CO3) and phosphoric acid (H3PO4) in the presence of water to form dipotassium hydrogen phosphate (K2HPO4) and CO2. The molar ratio of the total quantity of phosphoric acid (H3PO4) used to the total quantity of potassium carbonate (K2CO3) used is greater than 1.00 and no more than 1.20, and the total quantity of water added, including any water contained in the phosphoric acid (H3PO4) used, is less than the quantity of water required to completely dissolve the total quantity of potassium carbonate (K2CO3) used in water at 20°C. The invention also relates to a liquid potassium phosphate fertiliser containing dipotassium hydrogen phosphate (K2HPO4). The liquid potassium phosphate fertiliser has a density of 1.59 g / cm3 or more at 20°C. The potassium content of the potassium phosphate liquid fertiliser, expressed as K2O equivalents, is 48.0% w / v K2O or more, and the phosphorus content of the liquid potassium phosphate fertiliser, expressed as P2O5 equivalents, is 38.0% w / v P2O5 or more.

Description

[0001] HE 280 112 nl / n39

[0002] Potassium phosphate liquid fertilizer and methods for its production

[0003] DESCRIPTION

[0004] Technical field / subject of the invention

[0005] The present invention relates to a potassium phosphate liquid fertilizer with high mineral content, i.e., high salt concentration, high density, and a high potassium and phosphorus content, and to a process for producing such a potassium phosphate liquid fertilizer. The potassium phosphate liquid fertilizer can be used as a plant fertilizer, for example, for fertilizing cultivated land.

[0006] Furthermore, the present invention relates to a fertilizer set comprising potassium phosphate liquid fertilizer, the use of the potassium phosphate liquid fertilizer for the production of a ready-to-use aqueous solution of potassium phosphate liquid fertilizer and for fertilizing potting soil, in particular a growing area, with potassium and phosphorus, as well as a method for producing a ready-to-use aqueous solution of potassium phosphate liquid fertilizer and a method for fertilizing potting soil, in particular a growing area, with potassium and phosphorus.

[0007] Technical background

[0008] The prior art describes a variety of plant fertilizers containing the nutrients potassium, phosphorus and / or nitrogen, as well as methods for their production.

[0009] For reasons of economy and efficiency, it is advantageous to provide plant fertilizer as a concentrate with high mineral content (i.e., high salt concentration), high density, and a high content of essential nutrients such as potassium, phosphorus, and / or nitrogen. This concentrate can then be diluted by the user, such as a farmer or private individual, to create a ready-to-use aqueous solution. Providing a concentrate thus offers the advantage of reduced transport costs and carbon dioxide (CO2) emissions due to the smaller volume of fertilizer.

[0010] Furthermore, it is advantageous if the plant fertilizer is easy to dose and can be easily adjusted to the desired salt concentration, the desired concentration of nutrients, and the desired ratios of nutrients before use.

[0011] One way to achieve high mineral content and a high nutrient content is, in principle, to use solid salts containing the nutrients potassium, phosphorus and / or nitrogen, such as potassium dihydrogen phosphate (pure density: 2.34 g / cm³). 3 ), dipotassium hydrogen phosphate (pure density: 2.44 g / cm³) 3 ) or ammonium phosphate (pure density: 1.61 g / cm³) 3 However, the bulk density of particulate solids, such as those used as plant fertilizers, is generally significantly lower than the density of the corresponding substances in their pure form. Therefore, the actual mineral content and the concentration of nutrients per unit volume are lower than assumed for the pure substances. This results in higher costs and increased carbon dioxide (CO2) emissions during transport due to the larger volume of the particulate solids compared to the pure substances.

[0012] Furthermore, solid fertilizers, such as those described in Chinese patent application CN 108929118 A, are more complicated to handle than liquid fertilizers. When applied as a solid to the soil, for example in cultivated areas, solid fertilizers are more difficult to dose and distribute evenly. Additionally, depending on wind strength, solid fertilizers can be blown away by wind drift or erosion of the applied fertilizer. Alternatively, the solid fertilizers can be dissolved in water before use, but this requires an additional dissolving step and thus reduces the time and energy efficiency of application.Depending on the salts used, the dissolution step may involve significant heat generation, requiring the fertilizer solution to be cooled before use, or, in the case of an endothermic dissolution reaction, requiring the input of energy.

[0013] Suspensions of fertilizer components, particularly salts containing the nutrients potassium, phosphorus, and / or nitrogen, are also known and described, for example, in US 2002 / 0129632 Al or US 2003 / 0029211 Al. Suspensions are more complicated to handle than liquid fertilizers, in which the fertilizer components are completely dissolved. Due to the sedimentation of the solids they contain, suspensions are generally unstable, making it more difficult to apply the fertilizer components evenly. To produce stable suspensions, stabilizers are required in addition to the fertilizer components, which also reduces the cost-effectiveness of the fertilizer. Furthermore, clogging of lines and nozzles can occur when applying fertilizer suspensions. This also happens, for example, when applying liquid manure, an organic fertilizer suspension.

[0014] Since plant fertilization generally requires the three main nutrients potassium, phosphorus, and nitrogen, the prior art, as exemplified by WO 2023 / 104299 Al, describes a variety of NPK fertilizers containing these nutrients in combination. However, NPK fertilizers contain the three nutrients in a defined ratio. Therefore, when using an NPK fertilizer, the ratios of these nutrients cannot be adjusted to the specific soil conditions of the areas to be fertilized, such as cultivated fields, unless other fertilizer components are added. From this perspective, it is advantageous to provide plant fertilizers containing only two of the nutrients, for example, potassium and phosphorus or nitrogen and phosphorus. These fertilizers can then be combined appropriately to adapt the nutrient ratios to the specific soil conditions.

[0015] Furthermore, conventional methods for producing plant fertilizers often require controlling reaction temperatures by cooling (in the case of exothermic reactions) or heating (in the case of endothermic reactions) and keeping them within suitable ranges. Due to the associated energy consumption, these measures increase production costs and can have a negative impact on the climate footprint.

[0016] Summary of the invention

[0017] Against this background, the present invention aims to provide a potassium phosphate fertilizer that avoids or reduces the disadvantages of the prior art. In particular, the present invention aims to reduce the costs and CO2 footprint of transporting the fertilizer from the place of production to the user.

[0018] A further object of the present invention is to provide a process for producing such a potassium phosphate fertilizer, which is also characterized by a good energy and CO2 balance. This object is achieved by the potassium phosphate liquid fertilizer and the process for producing a potassium phosphate liquid fertilizer according to the claims. The potassium phosphate liquid fertilizer according to the invention has a very high minerality and density and a very high potassium and phosphorus content.

[0019] The term "potassium phosphate liquid fertilizer" is to be understood, according to common usage, as meaning that - apart from unavoidable impurities - it contains only the nutrients potassium and phosphorus.

[0020] The present invention relates in particular to the following:

[0021]

[0001] Process for producing a potassium phosphate liquid fertilizer, comprising the reaction of potassium carbonate (K2CO3) and phosphoric acid (H3PO4) in the presence of water to form dipotassium hydrogen phosphate (K2HPO4) and CO2,

[0022] wherein the molar ratio of the total amount of phosphoric acid (H3PO4) used to the total amount of potassium carbonate (K2CO3) used is greater than 1.00 and 1.20 or less, and

[0023] the total amount of water added, including any water contained in the phosphoric acid (H3PO4) used, is lower than the amount of water required to completely dissolve the total amount of potassium carbonate (K2CO3) used in water at 20°C.

[0024]

[0002] Method according to

[0001] , wherein

[0025] The mixing of potassium carbonate (K2CO3) and phosphoric acid (H3PO4) is carried out such that the pH value during the mixing and reaction of potassium carbonate (K2CO3) and phosphoric acid (H3PO4) does not exceed 9.2, preferably 8.6, wherein the pH value during the mixing and reaction of potassium carbonate (K2CO3) and phosphoric acid (H3PO4) is measured by means of a pH electrode at a point where potassium carbonate (K2CO3) and phosphoric acid (H3PO4) are mixed.

[0026]

[0003] A process for producing a potassium phosphate liquid fertilizer according to

[0001] or

[0002] , comprising at least the following steps:

[0027] a) Substitution of phosphoric acid (H3PO4),

[0028] b) Mixing the potassium carbonate (K2CO3) into the phosphoric acid (H3PO4) while stirring, preferably dissolving a portion of the potassium carbonate (K2CO3) in water before adding it and adding another portion of the potassium carbonate (K2CO3) in solid form.

[0029]

[0004] Process for producing a potassium phosphate liquid fertilizer according to

[0001] ,

[0002] or

[0003] , wherein the molar ratio of the total amount of phosphoric acid (H3PO4) used to the total amount of potassium carbonate (K2CO3) used is 1.02 or more and 1.18 or less, preferably 1.05 or more and 1.15 or less, and more preferably 1.06 or more and 1.12 or less.

[0030]

[0005] A process for producing a potassium phosphate liquid fertilizer according to

[0001] to

[0004] , wherein the total amount of water added, including any water contained in the phosphoric acid (H3PO4) used, corresponds to 80.0% to 95.0%, preferably 85.0% to 92.0% of the amount of water required to dissolve the total amount of potassium carbonate (K2CO3) used in water at 20°C.

[0031]

[0006] Method for producing a potassium phosphate liquid fertilizer according to one of claims

[0003] to

[0005] , wherein 60% to 85% of the potassium carbonate (KgCOg ) is dissolved in water before being added to the phosphoric acid (H3PO4 ) and 15% to 40% of the potassium carbonate (K2CO3) is added to the phosphoric acid (H3PO4) in solid form.

[0032]

[0007] Method for producing a potassium phosphate liquid fertilizer according to [3] to

[0006] , wherein step b) of mixing the potassium carbonate (K2CO3) into the phosphoric acid (H3PO4) is carried out by

[0033] b1) first, a portion of the potassium carbonate (K2CO3), which had been dissolved in water prior to the addition, was added to the phosphoric acid (H3PO4), and

[0034] b2) the remaining part of the potassium carbonate (K2CO3) is then added in solid form to the phosphoric acid (H3PO4).

[0035]

[0008] Process for producing a potassium phosphate liquid fertilizer according to

[0001] to

[0007] , wherein the CO2 formed during the reaction of potassium carbonate (K2CO3) and phosphoric acid (H3PO4) is separated and preferably used as a raw material.

[0036]

[0009] Process for the production of a potassium phosphate liquid fertilizer according to

[0001] to

[0008] , wherein the starting materials are exclusively potassium carbonate (K2CO3) and phosphoric acid (H3PO4) reacted in the presence of water.

[0037]

[0010] Potassium phosphate liquid fertilizer containing dipotassium hydrogen phosphate (K2HPO4 ), wherein

[0038] i) the potassium phosphate liquid fertilizer has a density of 1.59 g / cm³ at 20°C 3 or more

[0039] ii) the potassium content of the potassium phosphate liquid fertilizer, expressed in K2O equivalents, is 48.0% w / v K2O or more, and

[0040] iii) the phosphorus content of the potassium phosphate liquid fertilizer, expressed in P2O5 equivalents, is 38.0% w / v P2O5 or more.

[0011] Potassium phosphate liquid fertilizer according to

[0010] , wherein the pH of an aqueous solution of the potassium phosphate liquid fertilizer, obtained by mixing a certain volume of the potassium phosphate liquid fertilizer with 50 times the volume of double-distilled water, measured by a pH electrode at a solution temperature of 20 °C, is 7.2 or more and 7.8 or less, preferably 7.3 or more and 7.7 or less, more preferably 7.4 or more and 7.6 or less.

[0041]

[0012] Potassium phosphate liquid fertilizer according to

[0010] or

[0011] , wherein the potassium phosphate liquid fertilizer has a density of 1.60 g / cm³ at 20 °C 3 or more, preferably 1.61 g / cm³ 3 or more, preferably 1.62 g / cm² 3 or more, even more preferably 1.63 g / cm² 3 or more, even more preferably 1.64 g / cm² 3or more, e.g. at least 1.65 g / cm² 3 or at least 1.67 g / cm³ 3 exhibits.

[0042]

[0013] Potassium phosphate liquid fertilizer according to

[0010] ,

[0011] or

[0012] , wherein the potassium content of the potassium phosphate liquid fertilizer, expressed in K2O equivalents, is 49.0% w / v K2O or more, preferably 50.0% w / v K2O or more, more preferably

[0043] 51.0% w / v K2O or more, and even more preferably 52.0% w / v K2O or more.

[0044]

[0014] Potassium phosphate liquid fertilizer according to one of

[0010] to

[0013] , wherein the phosphorus content of the potassium phosphate liquid fertilizer, expressed in P2O5 equivalents, is 39.0% w / v P2O5 or more, preferably 40.0% w / v P2O5 or more, more preferably 41.0% w / v P2O5 or more and even more preferably 42.0% w / v P2O5 or more.

[0045]

[0015] Potassium phosphate liquid fertilizer according to one of

[0010] to

[0014] , wherein the potassium phosphate liquid fertilizer is obtainable by the method according to one of

[0001] to

[0009] .

[0046]

[0016] Fertilizer set comprising: the potassium phosphate liquid fertilizer according to a

[0010] to

[0015] ; and

[0047] one or more additional fertilizer components (n).

[0048]

[0017] Use of the potassium phosphate liquid fertilizer according to

[0010] to

[0015] for the production of a ready-to-use aqueous solution of a potassium phosphate liquid fertilizer, wherein the aqueous solution of the potassium phosphate liquid fertilizer is obtained by mixing a certain volume of the potassium phosphate liquid fertilizer with water, preferably with three to 10000 times the volume of water.

[0049]

[0018] Use of the potassium phosphate liquid fertilizer according to

[0010] to

[0015] for fertilizing potting soil, in particular a growing area, with potassium and phosphorus.

[0050]

[0019] Method for producing a ready-to-use aqueous solution of a potassium phosphate liquid fertilizer, the method comprising:

[0051] the mixing of a certain volume of the potassium phosphate liquid fertilizer according to one of

[0010] to

[0015] with water, preferably with three to 10000 times the volume of water.

[0052]

[0020] Method for fertilizing potting soil, in particular a cultivation area, with potassium and phosphorus, wherein the method comprises:

[0053] The preparation of a ready-to-use aqueous solution of potassium phosphate liquid fertilizer by mixing a specific volume of the potassium phosphate liquid fertilizer according to

[0010] to

[0015] with water, preferably with three to 10,000 times the volume of water; and applying the ready-to-use aqueous solution of the potassium phosphate liquid fertilizer to the planting soil, in particular a cultivation area. The potassium phosphate liquid fertilizer of the present invention has a high mineral content, i.e., a high salt concentration, which results from the high density and the high potassium and phosphorus content. This has the advantage that, due to the comparatively small volume of the potassium phosphate liquid fertilizer, costs and CO2 emissions can be saved during transport.Furthermore, the potassium phosphate liquid fertilizer according to the invention can be easily adjusted to the desired salt concentration and the desired concentrations of the nutrients potassium and phosphorus by mixing it with water immediately before use. This dilution step requires neither cooling nor the input of thermal energy and is therefore more time- and energy-efficient than dissolving a solid. Moreover, due to its high mineral content and high potassium and phosphorus content, the potassium phosphate liquid fertilizer according to the invention is highly adaptable and very efficient. Depending on the nutrient requirements of the areas to be fertilized, the potassium phosphate liquid fertilizer according to the invention can be diluted with, for example, three to 10,000 times its volume of water. In addition, despite its high potassium and phosphorus content, the potassium phosphate liquid fertilizer according to the invention exhibits excellent storage stability.When stored at 20°C in a closed container, i.e., when water evaporation is prevented, no solids, e.g., salts, precipitate for several months, thus keeping the minerality, i.e., salt concentration, of the solution constant.

[0054] The potassium phosphate liquid fertilizer according to the invention preferably contains only the nutrients potassium and phosphorus, but no other nutrients such as nitrogen, sulfur, calcium, or magnesium. Thus, the amounts of potassium and phosphorus required for fertilization, as well as the required amounts of other nutrients, can be independently adjusted to the soil conditions of the areas to be fertilized, e.g., cultivated fields, by combining the potassium phosphate liquid fertilizer according to the invention with suitable additional fertilizer components, for example, nitrogen fertilizers.

[0055] The potassium phosphate liquid fertilizer according to the invention is preferably obtained by the process according to the invention for producing a potassium phosphate liquid fertilizer. In this process, potassium carbonate (KgCOg) and phosphoric acid (H3PO4) are reacted with each other in such a way that a potassium phosphate liquid fertilizer with high minerality, i.e., high salt concentration, high density and a high potassium and phosphorus content is obtained.

[0056] A further advantage of the process according to the invention is that, due to the coupling of an exothermic reaction in the conversion of potassium carbonate (KgCOg) and phosphoric acid (H3PO4), namely the formation of potassium dihydrogen phosphate (KH2PO4), and an endothermic reaction, namely the dissolution of potassium dihydrogen phosphate (KH2PO4) and the formation of dipotassium hydrogen phosphate (K2HPO4), no thermal energy needs to be supplied. In this way, the energy consumption of the process according to the invention can be reduced compared to conventional processes for the production of potassium phosphate fertilizers, thereby reducing production costs and the CO2 footprint.

[0057] In addition, the COg formed as a by-product in the reaction of potassium carbonate (KgCOg) and phosphoric acid (H3PO4) can be separated and, if necessary, used as a high-purity raw material for further processing, for example in the formation of methane, kerosene, urea or carbonates.

[0058] This further improves the CO2 balance of the inventive process and avoids environmental pollution caused by the inventive process. Detailed description of the invention

[0059] I. Method for the production of a potassium phosphate liquid fertilizer

[0060] The present invention relates to a process for producing a potassium phosphate liquid fertilizer.

[0061] The process according to the invention for producing a potassium phosphate liquid fertilizer comprises the reaction of potassium carbonate (KgCOg) and phosphoric acid (H3PO4) in the presence of water to potassium phosphate salts and carbon dioxide (CO2). A liquid fertilizer according to the invention is understood to be a fertilizer in which the fertilizer components contained, in particular salts, are present in dissolved form at a temperature of 20°C such that the liquid fertilizer appears as a clear solution.

[0062] According to the process according to the invention, the molar ratio of the total amount of phosphoric acid (H3PO4) used to the total amount of potassium carbonate (K2CO3) used is greater than 1.00 and 1.20 or less. When the molar ratio of phosphoric acid (H3PO4) to potassium carbonate (KgCOg) is in this range, the reaction of potassium carbonate (KgCOg) and phosphoric acid (H3PO4) mainly forms dipotassium hydrogen phosphate (K2HPO4). Dipotassium hydrogen phosphate (K2HPO4) has a very good solubility in water at 20°C (1600 g / L), which enables the production of a potassium phosphate liquid fertilizer with high mineral content (i.e., high salt concentration) and high density. If the molar ratio of phosphoric acid (H3PO4 ) to potassium carbonate (KgCOg) is greater than 1.20, the proportion of potassium dihydrogen phosphate (KH2PO4 ) formed in the potassium phosphate liquid fertilizer is too high.Potassium dihydrogen phosphate (KH₂PO₄) has a significantly lower solubility in water at 20°C (222 g / L) than dipotassium hydrogen phosphate (K₂HPO₄), meaning that a high mineral content (i.e., high salt concentration) and a high density of the potassium phosphate liquid fertilizer cannot be achieved. Furthermore, the potassium content of potassium dihydrogen phosphate (KH₂PO₄) is lower than that of dipotassium hydrogen phosphate (K₂HPO₄), thus preventing a high potassium content in the potassium phosphate liquid fertilizer. However, if the molar ratio of phosphoric acid (H₃PO₄) to potassium carbonate (KgCO₃) is 1.00 or less, the reaction of potassium carbonate (KgCO₃) and phosphoric acid (H₃PO₄) results in the formation of tripotassium phosphate (K₃PO₄).

[0063] Tripotassium phosphate (K3PO4) also exhibits a significantly lower solubility in water at 20°C (508 g / L) than dipotassium hydrogen phosphate (K2HPO4). Therefore, the formation of tripotassium phosphate (K3PO4) reduces the overall solubility of the potassium phosphate salts formed, thus lowering the achievable mineral content (i.e., salt concentration) and density of the potassium phosphate liquid fertilizer. Depending on the amount of water present, some of the potassium phosphate salts precipitate out during the formation of tripotassium phosphate (K3PO4), resulting in a turbid suspension. Given that the reaction of potassium carbonate (KgCOg) and phosphoric acid (H3PO4) should primarily produce dipotassium hydrogen phosphate (K2HPO4) to achieve high mineral content (i.e., salt concentration) and density, this is a significant drawback.To ensure a high salt concentration, high density, and high potassium and phosphorus content in the potassium phosphate liquid fertilizer, the molar ratio of the total amount of phosphoric acid (H3PO4) used to the total amount of potassium carbonate (KgCOg) used is preferably 1.02 or more and 1.18 or less, more preferably 1.05 or more and 1.15 or less, and even more preferably 1.06 or more and 1.12 or less. The potassium phosphate liquid fertilizer according to the invention may contain residual amounts of KgCOg and H3PO4, which, however, do not react further. A possible explanation for this is the small amounts of water used in the process. According to the process according to the invention, the reaction of potassium carbonate (KgCOg) and phosphoric acid (H3PO4) takes place in the presence of water, wherein the total amount of added water, including any...The amount of water contained in the phosphoric acid (H3PO4) used is lower than the amount of water required to completely dissolve the total amount of potassium carbonate (K2CO3) used in water at 20°C (the solubility of potassium carbonate (KgCOg) in water at 20°C is 1120 g / L). In this way, the total amount of water in the reaction mixture and the resulting potassium phosphate liquid fertilizer is kept low, resulting in a potassium phosphate liquid fertilizer with high minerality, i.e., high salt concentration, high density, and high potassium and phosphorus content. To achieve these properties while simultaneously ensuring the complete solubility of the fertilizer components, especially the potassium phosphate salts formed, the total amount of added water, including any water contained in the phosphoric acid (H3PO4), is lower than the amount of water required to completely dissolve the total amount of potassium carbonate (K2CO3) used in water at 20°C (the solubility of potassium carbonate (KgCOg) in water at 20°C is 1120 g / L).Water contained in the phosphoric acid (H3PO4) used, preferably 80.0% to 95.0%, more preferably 85.0% to 92.0% of the amount of water required to dissolve the total amount of potassium carbonate (KgCOg) used in water at 20°C.

[0064] The density of a saturated solution of dipotassium hydrogen phosphate (K2HPO4 ) at 20°C is

[0065] 1.57 g / cm³. According to the inventive process for producing a potassium phosphate liquid fertilizer, a potassium phosphate liquid fertilizer with a higher density of 1.59 g / cm³ or more can surprisingly be obtained.

[0066] Thus, according to the inventive method, a potassium phosphate liquid fertilizer with excellent minerality, i.e., high salt concentration, high density and a high potassium and phosphorus content, can be produced.

[0067] The mixing and reaction of potassium carbonate (KgCOg) and phosphoric acid (H3PO4) is preferably carried out in such a way that pH values ​​at which tripotassium phosphate (K3PO4) is formed are not exceeded, either temporarily or locally. Accordingly, the addition rate of potassium carbonate (KgCOg) is preferably adjusted, regardless of whether it is present in liquid form as a solution or in solid form. When selecting the reactor and the means for stirring the reactants, care is preferably taken to ensure the most homogeneous mixing possible in order to avoid the local formation of undesirably high pH values. A mechanical stirrer, such as an anchor, screw, or blade stirrer, can be used to stir the reactor.

[0068] Preferably, the process according to the invention for producing a potassium phosphate liquid fertilizer is carried out using a reaction system without a mechanical agitator, with a recirculation system, for example comprising a submersible jet and a recirculation pump. A suitable reaction system is described in the simultaneously pending application PCT / EP2023 / 077596, the disclosure of which is incorporated by reference. The use of a reaction system without a mechanical agitator has the advantage that contamination by sealing agents, e.g., oil, which are commonly used to seal the agitator shaft, can be prevented. Furthermore, uncontrolled gas escape, e.g., of reaction gas and / or solvent vapors, via the agitator shaft can be prevented.

[0069] In one embodiment of the process according to the invention, the mixture of reactants is stirred using a reaction system with a recirculating system such that a flow with transitional characteristics between laminar and turbulent flow (Reynolds number between 2300 and 3000) or a turbulent flow is obtained (Reynolds number > approx. 3000). The mixing and reaction are further preferably carried out under continuous monitoring of the pH value of the reaction mixture. In this way, the mixing and reaction of potassium carbonate (KgCOg) and phosphoric acid (H3PO4) can be controlled so that pH values ​​at which tripotassium phosphate (K3PO4) is formed are not exceeded, even temporarily and / or locally. Preferably, the mixing and reaction of potassium carbonate (KgCOg) and phosphoric acid (H3PO4) is carried out such that the pH value does not exceed 9.2, more preferably 8.6.The pH value is measured during the mixing and reaction of potassium carbonate (KgCOg) and phosphoric acid (H3PO4) using a pH electrode at the point where the potassium carbonate (K2CO3) and phosphoric acid (H3PO4) are mixed. A person skilled in the art can ensure, by appropriately positioning one or more pH electrodes in the reactor mixture, that the pH value preferably does not exceed 9.2, more preferably 8.6, locally during the mixing and reaction of potassium carbonate (KgCOg) and phosphoric acid (H3PO4).

[0070] The inventive process for producing a potassium phosphate liquid fertilizer preferably comprises at least the following steps:

[0071] a) Presentation of phosphoric acid (H3PO4),

[0072] b) Mixing the potassium carbonate (KgCOg) into the phosphoric acid (H3PO4 ) while stirring.

[0073] When potassium carbonate (KgCOg) is mixed into phosphoric acid (H3PO4), potassium dihydrogen phosphate (KH2PO4) is initially formed. Due to its relatively low solubility (222 g / L in water at 20°C), this precipitates out. The formation of potassium dihydrogen phosphate (KH2PO4) is exothermic, so the temperature of the reaction mixture can rise to up to 90°C during the formation of potassium dihydrogen phosphate (KH2PO4), and preferably to less than 85°C, more preferably to less than 75°C. With increasing amounts of potassium carbonate (KgCOg) added and the associated increase in pH of the reaction mixture, potassium dihydrogen phosphate (KH2PO4) is converted to dipotassium hydrogen phosphate (K2HPO4), which, due to its higher solubility (1600 g / L in water at 20°C), can dissolve again in the reaction mixture.The dissolution of potassium dihydrogen phosphate (KH₂PO₄) and the formation of dipotassium hydrogen phosphate (K₂HPO₄) proceed endothermically, utilizing the heat of reaction from the formation of potassium dihydrogen phosphate (KH₂PO₄), so that the temperature of the reaction mixture decreases again during the formation of dipotassium hydrogen phosphate (K₂HPO₄). Due to the coupling of an exothermic reaction in the conversion of potassium carbonate (KgCO₂) and phosphoric acid (H₃PO₄), namely the formation of potassium dihydrogen phosphate (KH₂PO₄), and an endothermic reaction, namely the dissolution of potassium dihydrogen phosphate (KH₂PO₄) and the formation of dipotassium hydrogen phosphate (K₂HPO₄), no cooling or thermal energy input is required if the reaction is appropriately controlled. It is therefore a preferred feature of the process according to the invention that no cooling or heating devices are used for temperature control of the reaction.In this way, the energy consumption of the process according to the invention can be reduced compared to conventional processes for the production of potassium phosphate fertilizers, thereby reducing production costs and environmental impact.

[0074] Preferably, a portion of the potassium carbonate (KgCOg) is dissolved in water before being added to the phosphoric acid (H3PO4), and another portion is added to the phosphoric acid (H3PO4) in solid form. It is more preferred that 60% to 85% of the potassium carbonate (KgCOg) is dissolved in water before being added to the phosphoric acid (H3PO4), and that 15% to 40% of the potassium carbonate (KgCOg) is added to the phosphoric acid (H3PO4) in solid form. According to the process according to the invention, the total amount of water added, including any water contained in the phosphoric acid (H3PO4) used, is less than the amount of water required to completely dissolve the total amount of potassium carbonate (K2CO3) used in water at 20°C. This can be achieved, for example, by adding some of the potassium carbonate (KgCOg) in solid form to the phosphoric acid (H3PO4 ).Since the reaction mixture begins to foam when potassium carbonate (KgCOg) in solid form is added to the phosphoric acid (H3PO4), preferably as large a portion as possible of the potassium carbonate (KgCOg) used is added in dissolved form. Preferably, the portion of the potassium carbonate (KgCOg) dissolved in water is added to the phosphoric acid (H3PO4) first, and then the remaining portion of the potassium carbonate (KgCOg) is added to the phosphoric acid (H3PO4) in solid form.

[0075] The COg formed as a byproduct in the reaction of potassium carbonate (KgCOg) and phosphoric acid (H3PO4) is preferably separated. For this purpose, the process according to the invention is preferably carried out in a closed system. The resulting high-purity COg, which does not contain the usual gaseous impurities such as atmospheric nitrogen, is a valuable raw material. This is preferably further processed, for example in the formation of methane, kerosene, urea, or carbonates.

[0076] This allows the CO2 balance of the inventive process to be further improved and avoids COg pollution of the environment by the inventive process.

[0077] Preferably, the process according to the invention comprises exclusively the reaction of potassium carbonate (KgCOg) and phosphoric acid (H3PO4 ) in the presence of water.

[0078] Accordingly, according to the invention, preferably no further components, such as further potassium- or phosphorus-containing compounds, e.g., further potassium salts, potassium hydroxide (KOH), phosphonic acid (H3PO3), or phosphinic acid (H3PO2), and in particular no compounds containing further nutrients, e.g., nitrogen, sulfur, calcium, or magnesium, are added. In this way, a potassium phosphate liquid fertilizer with high minerality, i.e., high salt concentration, and high density can be obtained, which contains only potassium and phosphorus in high concentrations as nutrients and no further nutrients, e.g., nitrogen, sulfur, calcium, or magnesium.

[0079] II. Potassium phosphate liquid fertilizer

[0080] The present invention further relates to a potassium phosphate liquid fertilizer.

[0081] According to the invention, a liquid fertilizer is understood to be a fertilizer in which the fertilizer components, in particular salts, are present in dissolved form at a temperature of 20°C, such that the liquid fertilizer appears as a clear solution. A clear solution is present if, upon visual inspection at a temperature of 20°C, the potassium phosphate liquid fertilizer appears free of particles and droplets, and no particles (precipitation of solids) and / or droplets form when the potassium phosphate liquid fertilizer is cooled to 17°C for 10 minutes. Suspensions and emulsions that do not meet this definition do not fall under the inventive definition of a liquid fertilizer.

[0082] The potassium phosphate liquid fertilizer according to the invention contains dipotassium hydrogen phosphate (K₂HPO₄). Preferably, the potassium phosphate liquid fertilizer according to the invention consists of 45% or more by mass of dipotassium hydrogen phosphate (K₂HPO₄), more preferably 50% or more by mass, and even more preferably 52% or more by mass. The potassium phosphate liquid fertilizer according to the invention has a density of 1.59 g / cm³ or more at 20°C. According to preferred embodiments, the density is 1.60 g / cm³ or more, preferably 1.61 g / cm³ or more, more preferably 1.62 g / cm³ or more, even more preferably 1.63 g / cm³ or more, and even more preferably 1.64 g / cm³ or more, e.g., at least 1.65 g / cm³ or at least 1.67 g / cm³. In one embodiment of the invention, the potassium phosphate liquid fertilizer according to the invention has a density of no more than 1.70 g / cm³ at 20°C.

[0083] The potassium content of the potassium phosphate liquid fertilizer according to the invention, expressed in K₂O equivalents, is 48.0% w / v K₂O or more. According to preferred embodiments, the potassium content is 49.0% w / v K₂O or more, preferably 50.0% w / v K₂O or more, and more preferably 51.0% w / v K₂O or more. According to one embodiment of the invention, the value of 54.0% w / v K₂O or 52.0% w / v K₂O is not exceeded.

[0084] The phosphorus content of the potassium phosphate liquid fertilizer according to the invention, expressed in PgOg equivalents, is 38.0% w / v PgOg or more. According to preferred embodiments, the phosphorus content is 39.0% w / v P₂O₅ or more, preferably 40.0% w / v P₂O₅ or more, and more preferably 41.0% w / v P₂O₅ or more. According to one embodiment of the invention, the value of 44.0% w / v P₂O₅ or 42.0% w / v P₂O₅ is not exceeded.

[0085] The potassium phosphate liquid fertilizer according to the invention, containing dipotassium hydrogen phosphate (K₂HPO₄), has a high density and a high potassium and phosphorus content, and thus a high mineral content, i.e., salt concentration. Due to the comparatively small volume of the potassium phosphate liquid fertilizer according to the invention, costs and CO₂ can be saved during transport. Furthermore, the potassium phosphate liquid fertilizer according to the invention can be easily adjusted to the desired salt concentration and the desired concentrations of the nutrients potassium and phosphorus immediately before use by mixing it with water. The dilution step requires neither cooling nor the input of thermal energy and is therefore more time- and energy-efficient than dissolving a solid. Moreover, due to its high mineral content and high potassium and phosphorus content, the potassium phosphate liquid fertilizer according to the invention is easily adaptable and very efficient.Depending on the nutrient requirements of the areas to be fertilized, the potassium phosphate liquid fertilizer according to the invention can be diluted with, for example, three to 10,000 times its volume of water. Furthermore, despite its high potassium and phosphorus content, the potassium phosphate liquid fertilizer according to the invention exhibits excellent storage stability. When stored at 20°C in a closed container, i.e., when water evaporation is prevented, no solids, such as salts, precipitate out for several months, thus maintaining a constant mineral content, i.e., salt concentration, of the solution.

[0086] According to a preferred embodiment of the potassium phosphate liquid fertilizer according to the invention, an aqueous solution of the potassium phosphate liquid fertilizer, obtained by mixing a certain volume of the potassium phosphate liquid fertilizer with 50 times the volume of double-distilled water, has a pH value, measured by means of a pH electrode at a solution temperature of 20°C, of ​​7.2 to 7.8, preferably of 7.3 to 7.7 and more preferably of 7.4 to 7.6.

[0087] Due to their neutral to slightly alkaline pH values, dilute aqueous solutions of the potassium phosphate liquid fertilizer according to the invention are therefore very well suited for fertilizing potting soil, for example, cultivated areas. The potassium phosphate liquid fertilizer according to the invention can be obtained by the inventive process for producing a potassium phosphate liquid fertilizer.

[0088] The potassium phosphate liquid fertilizer according to the invention preferably contains only the nutrients potassium and phosphorus, but no other nutrients such as nitrogen, sulfur, calcium, or magnesium (which are sometimes referred to as "macronutrients"). Thus, the amounts of potassium and phosphorus required for fertilization, as well as the required amounts of other nutrients, can be adjusted independently of one another to the soil properties of the areas to be fertilized, e.g., by combining the potassium phosphate liquid fertilizer according to the invention with one or more suitable additional fertilizer components, containing, for example, nitrogen, sulfur, calcium, or magnesium.

[0089] Cultivated areas can be adapted. The potassium phosphate liquid fertilizer according to the invention is compatible with a variety of other fertilizer components, e.g. also so-called.

[0090] “Micronutrients”, such as boron, copper, manganese, molybdenum, zinc or selenium.

[0091] After suitable dilution of the potassium phosphate liquid fertilizer according to the invention with water and mixing with other fertilizer components, e.g., aqueous solutions of macronutrients and / or micronutrients, ready-to-use so-called "tank mixtures" are preferably obtained. The production of tank mixtures, which ideally contain all the necessary nutrients, has the advantage that they can be applied to the areas to be fertilized, e.g., arable land, in a single step. This saves the farmer time and allows for optimal use of the available fertilization windows. Furthermore, the potassium phosphate liquid fertilizer according to the invention can be mixed with commercially available plant protection products, provided that no precipitation or chemical reactions occur.Applying fertilizer components and plant protection products simultaneously in a tank mix leads to further time savings for the farmer and improved utilization of available time windows.

[0092] III. Fertilizer Set

[0093] The present invention further relates to a fertilizer formulation.

[0094] The fertilizer composition according to the invention comprises the potassium phosphate liquid fertilizer according to the invention and one or more further fertilizer components (n).

[0095] By combining the potassium phosphate liquid fertilizer according to the invention, containing the nutrients potassium and phosphorus, with one or more further fertilizer components, which contain, for example, one or more of the nutrients nitrogen, sulfur, calcium or magnesium and / or the aforementioned “micronutrients”, the amounts of potassium and phosphorus required for fertilization, as well as the required amounts of other nutrients, can be adapted independently of one another to the soil properties of the areas to be fertilized, e.g., cultivated areas.

[0096] For combination with the potassium phosphate liquid fertilizer according to the invention, nitrogen fertilizers are suitable, for example, which mainly contain the nutrient nitrogen and preferably contain no other nutrients, such as potassium and phosphorus, or only in small quantities. Suitable nitrogen fertilizers contain, for example, the fertilizer components urea (CH4N2O), ammonium nitrate (NH4NO3), calcium ammonium nitrate (a mixture of 76% ammonium nitrate (NH4NO3) and 24% calcium carbonate (CaCO3)), or ammonium sulfate nitrate (NH4NO3). x·(NH4)2SO4, x=1-3) or an ammonium nitrate-urea solution (AHL). Furthermore, sulfur-containing fertilizers, which generally contain sulfate salts, e.g. ammonium sulfate ( (NH4 ) 2SO4 ), potassium sulfate (K2SO4 ) or magnesium sulfate (MgSO4 ), calcium-containing fertilizers, which contain e.g. water-soluble calcium oxide (CaO) or calcium nitrate (Ca(NO3)2 ), or magnesium-containing fertilizers, which contain e.g. magnesium oxide (MgO) or magnesium sulfate (MgSO4 ), are also suitable for combination with the potassium phosphate liquid fertilizer according to the invention.

[0097] With a view to saving time and optimally utilizing the time windows available for fertilization, the potassium phosphate liquid fertilizer according to the invention and the at least one other fertilizer component are mixed before application and applied, for example as a tank mix, in one step to the areas to be fertilized, e.g., cultivated fields. Alternatively, the potassium phosphate liquid fertilizer according to the invention and the one or more other fertilizer components can be applied separately to the areas to be fertilized, e.g., cultivated fields.

[0098] IV. Use of potassium phosphate liquid fertilizer

[0099] The potassium phosphate liquid fertilizer according to the invention can be used to produce a ready-to-use aqueous solution of a potassium phosphate liquid fertilizer.

[0100] The aqueous solution of the potassium phosphate liquid fertilizer can be obtained by mixing a certain volume of the potassium phosphate liquid fertilizer according to the invention with water.

[0101] Preferably, the potassium phosphate liquid fertilizer according to the invention is mixed with three to 10,000 times its volume of water to obtain a ready-to-use aqueous solution of potassium phosphate liquid fertilizer. By mixing the potassium phosphate liquid fertilizer according to the invention with water, a ready-to-use aqueous solution of potassium phosphate liquid fertilizer can be easily obtained, containing the desired salt concentration and the desired concentrations of the nutrients potassium and phosphorus. The dilution step requires neither cooling nor the input of thermal energy and is therefore more time- and energy-efficient than dissolving a solid.

[0102] Furthermore, the potassium phosphate liquid fertilizer according to the invention can be used to fertilize potting soil with potassium and phosphorus, in particular for fertilizing a cultivation area, e.g., a growing area in a greenhouse or an arable field, for example, in the cultivation of vegetables, fruit, or grain, e.g., in the cultivation of vegetables in a greenhouse or in the cultivation of fruit bushes or fruit trees. The phosphorus is applied in the form of "phosphate," whereby the term "phosphate" also includes hydrogenated forms such as phosphoric acid (H3PO4) and dihydrogen phosphate (H2PO4). - ) and monohydrogen phosphate (HPO4) 2- ), includes.

[0103] For this purpose, a ready-to-use aqueous solution of the potassium phosphate liquid fertilizer is first prepared by mixing a specific volume of the potassium phosphate liquid fertilizer according to the invention with water. Preferably, the potassium phosphate liquid fertilizer according to the invention is mixed with three to 10,000 times its volume of water to obtain a ready-to-use aqueous solution of potassium phosphate liquid fertilizer.

[0104] The ready-to-use aqueous solution of potassium phosphate liquid fertilizer is then applied to the planting soil, in particular a cultivation area. V. Method for producing a ready-to-use aqueous solution of potassium phosphate liquid fertilizer

[0105] The present invention further relates to a method for producing a ready-to-use aqueous solution of a potassium phosphate liquid fertilizer.

[0106] To prepare a ready-to-use aqueous solution of the potassium phosphate liquid fertilizer, a specific volume of the potassium phosphate liquid fertilizer according to the invention is mixed with water. Preferably, the potassium phosphate liquid fertilizer according to the invention is mixed with three to 10,000 times its volume of water to obtain a ready-to-use aqueous solution of the potassium phosphate liquid fertilizer.

[0107] By mixing the potassium phosphate liquid fertilizer according to the invention with water, a ready-to-use aqueous solution of potassium phosphate liquid fertilizer can be easily obtained, containing the desired salt concentration and the desired concentrations of the nutrients potassium and phosphorus. The dilution step requires neither cooling nor the input of thermal energy and is therefore more time- and energy-efficient than dissolving a solid.

[0108] VI. Methods for fertilizing potting soil with potassium and phosphorus

[0109] The present invention further relates to a method for fertilizing potting soil, in particular a cultivation area, with potassium and phosphorus.

[0110] The inventive method for fertilizing potting soil, in particular a cultivation area, with potassium and phosphorus comprises:

[0111] the production of a ready-to-use aqueous solution of potassium phosphate liquid fertilizer, and the application of the ready-to-use aqueous solution of potassium phosphate liquid fertilizer to the plant soil, in particular a cultivation area.

[0112] First, the ready-to-use aqueous solution of the potassium phosphate liquid fertilizer is prepared by mixing a specific volume of the potassium phosphate liquid fertilizer according to the invention with water. Preferably, the potassium phosphate liquid fertilizer according to the invention is mixed with three to 10,000 times its volume of water to obtain a ready-to-use aqueous solution of potassium phosphate liquid fertilizer.

[0113] The ready-to-use, aqueous solution of potassium phosphate liquid fertilizer is then applied to the plant soil, especially a growing area.

[0114] Examples

[0115] Measurement methods

[0116] Density:

[0117] The density of the potassium phosphate liquid fertilizer and the diluted solution of the potassium phosphate liquid fertilizer is measured at a temperature of 20°C using a hydrometer according to DIN 12790: 2019-12.

[0118] pH value and temperature:

[0119] To measure pH and temperature, a multiparameter meter with a pH electrode and a temperature sensor, such as a Pt100 temperature sensor, can be used. This allows for pH and temperature measurement as well as temperature compensation of the pH value, for example, in the range of -20°C to 120°C. For example, the Hanna Instruments HI5522-02, HI6222-02, or HI6542-02 meter can be used with a glass-body combination pH electrode (e.g., the Hanna Instruments HI1131B, filled with 3.5 M KCl electrolyte solution) and a temperature sensor (e.g., the Hanna Instruments HI7662-W or HI7662-TW).

[0120] Measurement of pH and temperature during the mixing and reaction of potassium carbonate (K2CO3) and phosphoric acid (H3PO4)

[0121] For reaction control, the pH value and temperature of the reaction mixture are measured during the mixing and reaction of potassium carbonate (K2CO3) and phosphoric acid (H3PO4) using the pH electrode and the temperature sensor at a point where potassium carbonate (K2CO3) and phosphoric acid (H3PO4) are mixed.

[0122] Measurement of the pH value of potassium phosphate liquid fertilizer and a diluted solution of potassium phosphate liquid fertilizer

[0123] The pH value of the potassium phosphate liquid fertilizer is measured using the pH electrode at a temperature of 20°C.

[0124] To prepare a diluted solution of the potassium phosphate liquid fertilizer, 1 part by volume of the potassium phosphate liquid fertilizer is diluted with 50 parts by volume of double-distilled water. The pH value of the diluted potassium phosphate liquid fertilizer solution is determined using a pH electrode at a temperature of 20°C according to...

[0125] Measured according to DIN 19263: 2007-05.

[0126] Potassium content:

[0127] The elemental potassium content (% w / w) in potassium phosphate liquid fertilizer is determined according to DIN EN ISO 11885 E22 2009-09. Multiplying the elemental potassium content by a factor of 1.205 yields the potassium content expressed in K₂O equivalents (% w / w K₂O). The potassium content expressed in volume-based K₂O equivalents (% w / v K₂O) is obtained by multiplying the potassium content expressed in K₂O equivalents (% w / w K₂O) by the density of the potassium phosphate liquid fertilizer.

[0128] Phosphorus content:

[0129] The elemental phosphorus content (% w / w) in potassium phosphate liquid fertilizer is determined according to DIN EN ISO 11885 E22 2009-09. Multiplying the elemental phosphorus content by a factor of 2.2914 yields the phosphorus content expressed in P₂O₅ equivalents (% w / w P₂O₅). The phosphorus content expressed in volume-based P₂O₅ equivalents (% w / v P₂O₅) is obtained by multiplying the phosphorus content expressed in P₂O₅ equivalents (% w / w P₂O₅) by the density of the potassium phosphate liquid fertilizer.

[0130] Visual inspection:

[0131] The reaction mixtures obtained in the examples can be used directly as potassium phosphate liquid fertilizer according to the invention. The reaction mixtures obtained in the examples and comparative examples were subjected to visual inspection and designated as clear solution or cloudy liquid according to the following criteria:

[0132] Clear solution: The potassium phosphate liquid fertilizer / reaction mixture appears particle- and droplet-free in visual inspection at a temperature of 20°C, and no particles (precipitation of solids) and / or droplets form when the potassium phosphate liquid fertilizer / reaction mixture is cooled down to 17°C for 10 minutes.

[0133] Cloudy liquid: The potassium phosphate liquid fertilizer / reaction mixture contains particles or droplets at 20°C according to visual inspection, or particles (precipitation of solids) and / or droplets form when the potassium phosphate liquid fertilizer / reaction mixture is cooled down to 17°C for 10 minutes.

[0134] EXAMPLE 1

[0135] For the reaction, a reactor with a volume of 12.0 L (diameter approx. 170 mm, height approx. 550 mm) and a vacuum pump connection was used, which was equipped with an anchor stirrer guided close to the wall and bottom with a wavelength of approx.

[0136] The reactor was equipped with a 550 mm diameter mixing head of approximately 150 mm and a stirring blade height of approximately 300 mm. In this reactor, 7900 g (57.16 mol) of potassium carbonate (K₂CO₃) and 7280 g of phosphoric acid (H₃PO₄, 85%; 63.14 mol) were reacted in the presence of water according to the process of the invention as follows, in order to produce a potassium phosphate liquid fertilizer containing dipotassium hydrogen phosphate (K₂HPO₄). The quantities used thus correspond to a molar ratio of phosphoric acid (H₃PO₄) to potassium carbonate (K₂CO₃) of 1.10.

[0137] Step a): In a first step, 7280 g of phosphoric acid (H3PO4, 85%) were placed in the reactor (temperature: 30.8 °C).

[0138] Step bl): In the next step, 6000 g of potassium carbonate (K₂CO₃) were dissolved in 5350 g of water (theoretically: 52.9% w / w K₂CO₃ in water, a total of 11350 g), whereby the temperature of the resulting K₂CO₃ solution rose to over 60°C. Due to the temperature increase, 74 g of water evaporated, so that subsequently a total of 11276 g of K₂CO₃ solution in water was added to the phosphoric acid (H₃PO₄, 85%).

[0139] The KgCOg solution was continuously added to the phosphoric acid (H3PO4, 85%) with stirring using an anchor stirrer at a speed of 110 rpm, according to the addition scheme shown in Table 1, before the temperature of the KgCOg solution had dropped below 35°C. During the addition of the KgCOg solution, a vacuum was applied to the reactor using a vacuum pump. At regular intervals, the amount of KgCOg solution added, the temperature and pH of the reaction mixture, and the pressure in the reactor and at the vacuum pump were measured. The corresponding values ​​are given in Table 1, where available.

[0140] After the KgCOg solution had been completely added, the vacuum applied to the reactor was removed and the 74 g of water that had evaporated due to the temperature increase of the KgCOg solution was added to the reaction mixture while stirring.

[0141] Step b2): In the next step, under normal pressure, 1900 g of potassium carbonate (KgCOg) as a solid was continuously added to the reaction mixture under stirring with the anchor stirrer at a speed of 110 rpm, according to the addition scheme shown in Table 1. Vigorous foaming was observed. The amount of solid KgCOg already added, as well as the temperature and pH of the reaction mixture, were again determined at regular intervals. The corresponding values ​​are given in Table 1, where available.

[0142] Step c): After the solid potassium carbonate (KgCOg) had been added, the reaction mixture was stirred until it cooled to a temperature of 43.5°C, at which point the pH of the reaction mixture rose to 8.74. The density of the resulting potassium phosphate liquid fertilizer at 43°C was 1.636 g / cm³.

[0143] After further cooling to 20°C, the potassium phosphate liquid fertilizer was obtained as a clear solution with a density of 1.648 g / cm³ and a pH of 8.8. The potassium content of the potassium phosphate liquid fertilizer, expressed in K₂O equivalents, was 50.0% w / v K₂O. The phosphorus content of the potassium phosphate liquid fertilizer, expressed in P₂O₅ equivalents, was 42.2% w / v P₂O₅.

[0144] To prepare a dilute solution of the potassium phosphate liquid fertilizer, 20 mL of the potassium phosphate liquid fertilizer were diluted with 1000 mL of double-distilled water. At a temperature of 20°C, the diluted solution had a density of 1.020 g / cm³ and a pH of 7.42.

[0145] The following Table 1 summarizes the essential reaction parameters of this embodiment for steps a) - c): Table 1

[0146] Total quantity of reactants (g) Order of addition and total quantity already added

[0147] H3PO4 (85%) 7280 7280

[0148] KgCOg solution 11276 0 2400 5000 7700 9700 11276

[0149] in water

[0150] Water (H₂O) 74 74

[0151] K₂CO₃ 1900 0 800 1900 (solid)

[0152] Step a bl bl bl bl bl bl bl b2 b2 b2 c Total time 0 0 11 21 33 42 46 46 50 72 100 127 (min)

[0153] Stirring speed 110 110 110 110 110 110 110 110 110 110 110 110 110 digkeit

[0154] (RPM)

[0155] Pressure (mbar) 676 / 964 / 965 / 960 / 960 / 920 / Normal pressure

[0156] in the reactor / 510 636 647 634 633 617

[0157] at the

[0158] vacuum pump

[0159] Temperature 30, 8 30, 8 68, 3 73, 5 81, 7 70, 7 62, 1 - 61, 2 56, 7 57, 3 43, 5 (°C)

[0160]

[0161] pH value 1.6 4.9 6.2 7.12 - 7.13 7.83 8.63 8.74 COMPARISON EXAMPLE 1

[0162] In the reactor described in Example 1, 7402 g (53.56 mol) of potassium carbonate (KgCOg) and 5683 g of phosphoric acid (H3PO4, 85%; 49.29 mmol) were reacted in the presence of water as follows. The quantities used thus correspond to a molar ratio of phosphoric acid (H3PO4) to potassium carbonate (K2CO3) of 0.92.

[0163] Step a) In a first step, 5483 g of phosphoric acid (H3PO4, 85%) were placed in the reactor.

[0164] Step b) In the next step, 7402 g of potassium carbonate (KgCOg) were dissolved in 6180 g of water (theoretically 54.5% w / w KgCOg in water, a total of 13582 g), whereby the temperature of the resulting KgCOg solution rose to over 60°C. Due to the temperature increase, 66 g of water evaporated, so that subsequently a total of 13516 g of KgCOg solution in water was added to the phosphoric acid (H3PO4, 85%).

[0165] The KgCOg solution was continuously added to the phosphoric acid (H3PO4, 85%) with an anchor stirrer at a speed of 110 rpm, according to the addition scheme shown in Table 2, before the temperature of the KgCOg solution had dropped below 35°C. During the addition of the KgCOg solution, a vacuum was applied to the reactor using a vacuum pump. The amount of KgCOg solution added, the temperature and pH of the reaction mixture, and the pressure in the reactor were measured at regular intervals. The corresponding values ​​are given in Table 2, where available. After the addition of the KgCOg solution was complete, the vacuum applied to the reactor was removed.

[0166] After the addition of the KgCOg solution was complete, the reaction mixture was obtained as a cloudy liquid, from which 981 g of solid and 16702 g of a clear solution were obtained by filtration. The clear solution obtained had a density of 1.556 g / cm³ and a pH of 9.3 at a temperature of 20°C.

[0167] The following Table 2 summarizes the key reaction parameters of this comparative example for steps a) - b): Table 2

[0168] Total quantity of reactants, order of addition, and total quantity already added

[0169] (G)

[0170] H3PO4 (85%) 5683 5683

[0171] K₂CO₃ solution 13516 0 1300 2400 3800 4800 6200 7400 9100 10100 11200 12100 13516 in water

[0172] Step abbbbbbbbbbbbb Total time 0 5 15 23 32 40 50 60 68 76 85 95 100 (min)

[0173] Stirring speed 110 110 110 110 110 110 110 110 110 110 110 110 110 digkeit

[0174] (RPM)

[0175] Pressure (mbar) 676 784 783 777 - 822 800 716 546 336 400 Standard pressure Temperature 29.5 54.1 62.7 66.4 70.7 71.1 64.8 55.1 50.3 49.6 49.8 - ( °C)

[0176]

[0177] pH value - - - - - 3.9 6.5 7.61 8.09 8.41 8.65 9.23 COMPARISON EXAMPLE 2

[0178] In the reactor described in Example 1, 7132 g (51.61 mol) of potassium carbonate (KgCOg) and 6571 g of phosphoric acid (H3PO4, 85%; 57.00 mmol) were reacted in the presence of water as follows. The quantities used thus correspond to a molar ratio of phosphoric acid (H3PO4) to potassium carbonate (K2CO3) of 1.10.

[0179] Step a) In a first step, 6571 g of phosphoric acid (H3PO4, 85%) were placed in the reactor.

[0180] Step b) In the next step, 7132 g of potassium carbonate (KgCOg) were dissolved in 6380 g of water (theoretically 52.8% w / w KgCOg in water, a total of 13492 g), whereby the temperature of the resulting KgCOg solution rose to over 60°C. Due to the temperature increase, 9 g of water evaporated, so that subsequently a total of 13483 g of KgCOg solution in water was added to the phosphoric acid (H3PO4, 85%).

[0181] The KgCOg solution was continuously added to the phosphoric acid (H3PO4, 85%) with an anchor stirrer at a stirring speed of 110 rpm, according to the addition scheme shown in Table 3, before the temperature of the KgCOg solution had dropped below 35°C. During the addition of the KgCOg solution, a vacuum was applied to the reactor using a vacuum pump. The amount of KgCOg solution added, the temperature and pH of the reaction mixture, and the pressure in the reactor were measured at regular intervals. The corresponding values ​​are given in Table 3, where available.

[0182] After the KgCOg solution had been completely added, the 9 g of water that had evaporated due to the temperature increase of the KgCOg solution were added to the reaction mixture while stirring. Step c): After the KgCOg solution had been completely added to the water, the reaction mixture was stirred further until it had cooled to a temperature of 19.6°C.

[0183] The potassium phosphate liquid fertilizer was obtained at 20°C as a clear solution with a density of 1.576 g / cm³ and a pH value of 8.7.

[0184] To prepare a dilute solution of the potassium phosphate liquid fertilizer, 20 mL of the potassium phosphate liquid fertilizer were diluted with 1000 mL of double-distilled water. At a temperature of 20°C, the diluted solution had a density of 1.018 g / cm³ and a pH of 7.56.

[0185] The following Table 3 summarizes the key reaction parameters of this comparative example for steps a) - c): Table 3

[0186] Total quantity of reactants, order of addition, and total quantity already added

[0187] (G)

[0188] H3PO4 (85%) 6571 6571

[0189] KgCOg solution 13483 0 2507 5337 7778 10255 12703 13483

[0190] in water

[0191] Water (H₂O) 9 9

[0192] Step abbbbbbbbbcc Total time 0 0 18 27 36 44 49 54 67 151 (min)

[0193] Stirring speed 110 110 110 110 110 110 110 110 110 digkeit

[0194] (RPM)

[0195] Pressure (mbar) 909 988 974 967 971 866 897 - 858 858 Temperature 25.1 63.8 75.4 88.5 54.6 51.1 51.1 - 27.9 19.6 ( °C)

[0196]

[0197] pH value - - - 2.14 5.48 7.55 8.35 8.51 - 8.63 8.70 Example 1 shows that by reacting potassium carbonate (KgCOg) and phosphoric acid (H3PO4) in the presence of water according to the process according to the invention, wherein the molar ratio of phosphoric acid (H3PO4) to potassium carbonate (K2CO3) is 1.10 and the total amount of water added is insufficient to completely dissolve the potassium carbonate (K2CO3) used in water at 20°C, a potassium phosphate liquid fertilizer with a high density at 20°C of 1.648 g / cm³, a high potassium content, expressed in KgO equivalents, of 50.0% w / v KgO and a high phosphorus content, expressed in PgOg equivalents, of 42.2% w / v is obtained. P2O5, and therefore a high mineral content, i.e.

[0198] Salt concentration can be obtained.

[0199] In Example 1, the temperature of the reaction mixture initially rises to 81.7 °C upon addition of the KgCOg solution to the phosphoric acid (H3PO4) due to the exothermic formation of potassium dihydrogen phosphate (KH2PO4). With the continued addition of the KgCOg solution or solid potassium carbonate (KgCOg) to the phosphoric acid (H3PO4) and the associated increase in pH, the initially formed potassium dihydrogen phosphate (KH2PO4) is converted to dipotassium hydrogen phosphate (K2HPO4) in an endothermic reaction, causing the temperature of the reaction mixture to decrease again. Furthermore, the pressure increase measured in the reactor upon addition of the KgCOg solution indicates the formation of carbon dioxide (CO2) (see Table 1).

[0200] In comparative example 1, however, where the molar ratio of phosphoric acid (H3PO4) to potassium carbonate (KgCOg) is only 0.92, resulting in an excess of potassium carbonate (KgCOg) being added to the phosphoric acid (H3PO4), tripotassium phosphate (K3PO4) is formed with increasing pH. The formation of tripotassium phosphate (K3PO4) reduces the overall solubility of the potassium phosphate salts formed, causing some of the potassium phosphate salts to precipitate and the reaction mixture to be obtained as a cloudy liquid (suspension). The clear solution obtained by filtration had a density of only 1.556 g / cm³ at 20°C. 3 as a result, a potassium phosphate liquid fertilizer with high minerality, i.e. salt concentration, and high density could not be obtained.

[0201] In comparative example 2, where the molar ratio of phosphoric acid (H3PO4) to potassium carbonate (K2CO3) is 1.10, analogous to example 1, no precipitation of solids is observed due to the formation of tripotassium phosphate (K3PO4) and the resulting decrease in the overall solubility of the potassium phosphate salts. However, due to the large total amount of water added, which is sufficient to completely dissolve the potassium carbonate (K2CO3) at 20°C, the resulting liquid potassium phosphate fertilizer has a density of only 1.576 g / cm³ at 20°C. 3 In comparative example 2, a potassium phosphate liquid fertilizer with high minerality (i.e., salt concentration) and high density could not be obtained.

[0202] In comparative examples 1 and 2, it can also be observed that the temperature of the reaction mixture initially rises upon addition of the K₂CO₃ solution to the phosphoric acid (H₃PO₄) due to the exothermic formation of potassium dihydrogen phosphate (KH₂PO₄) and subsequently falls again due to the endothermic conversion of potassium dihydrogen phosphate (KH₂PO₄) to dipotassium hydrogen phosphate (K₂HPO₄). Furthermore, in comparative examples 1 and 2, the pressure increase measured in the reactor upon addition of the KgCO₃ solution also indicates the formation of carbon dioxide (CO₂) (see Tables 2 and 3).

Claims

PATENT CLAIMS 1. A process for the production of a potassium phosphate liquid fertilizer, comprising the reaction of potassium carbonate (K2CO3) and phosphoric acid (H3PO4) in the presence of water to form dipotassium hydrogen phosphate (K2HPO4) and CO2, wherein the molar ratio of the total amount of phosphoric acid (H3PO4) used to the total amount of potassium carbonate (K2CO3) used is greater than 1.00 and 1.20 or less, and the total amount of water added, including any water contained in the phosphoric acid (H3PO4) used, is lower than the amount of water required to completely dissolve the total amount of potassium carbonate (K2CO3) used in water at 20°C.

2. Method according to claim 1, wherein the mixing of potassium carbonate (K2CO3) and phosphoric acid (H3PO4) is carried out in such a way that the pH value during the mixing and reaction of potassium carbonate (K2CO3) and phosphoric acid (H3PO4) does not exceed the value of 9.2, preferably 8.6, where the pH value is measured during the mixing and reaction of potassium carbonate (KgCOg) and phosphoric acid (H3PO4) using a pH electrode at a point where potassium carbonate (K2CO3) and phosphoric acid (H3PO4) are mixed.

3. A method for producing a potassium phosphate liquid fertilizer according to claim 1 or 2, comprising at least the following steps: a) Presentation of phosphoric acid (H3PO4), b) Mixing the potassium carbonate (K2CO3) into the phosphoric acid (H3PO4) while stirring, preferably dissolving a portion of the potassium carbonate (K2CO3) in water before adding it and adding another portion of the potassium carbonate (K2CO3) in solid form.

4. A process for producing a potassium phosphate liquid fertilizer according to claim 1, 2 or 3, wherein the molar ratio of the total amount of phosphoric acid (H3PO4) used to the total amount of potassium carbonate (K2CO3) used is 1.02 or more and 1.18 or less, preferably 1.05 or more and 1.15 or less, and more preferably 1.06 or more and 1.12 or less.

5. A method for producing a potassium phosphate liquid fertilizer according to any one of claims 1 to 4, wherein the total amount of water added, including any water contained in the phosphoric acid (H3PO4) used, corresponds to 80.0% to 95.0%, preferably 85.0% to 92.0% of the amount of water required to dissolve the total amount of potassium carbonate (K2CO3) used in water at 20°C.

6. A process for producing a potassium phosphate liquid fertilizer according to any one of claims 3 to 5, wherein 60% to 85% of the potassium carbonate (K2CO3) is dissolved in water before being added to the phosphoric acid (H3PO4) and 15% to 40% of the potassium carbonate (K2CO3) is added to the phosphoric acid (H3PO4) in solid form.

7. A method for producing a potassium phosphate liquid fertilizer according to any one of claims 3 to 6, wherein step b) of mixing the potassium carbonate (K2CO3) into the phosphoric acid (H3PO4) is carried out by b1) first adding a portion of the potassium carbonate (K2CO3), which has been dissolved in water prior to the addition, to the phosphoric acid (H3PO4), and b2) subsequently adding the remaining portion of the potassium carbonate (K2CO3) in solid form to the phosphoric acid (H3PO4).

8. A process for producing a potassium phosphate liquid fertilizer according to any one of claims 1 to 7, wherein the CO2 formed during the reaction of potassium carbonate (K2CO3) and phosphoric acid (H3PO4) is separated and preferably reused as a raw material.

9. A process for producing a potassium phosphate liquid fertilizer according to any one of claims 1 to 8, wherein the starting materials are exclusively potassium carbonate (K2CO3) and phosphoric acid (H3PO4) reacted in the presence of water.

10. Potassium phosphate liquid fertilizer containing dipotassium hydrogen phosphate (K2HPO4), wherein i) the potassium phosphate liquid fertilizer has a density of 1.59 g / cm³ at 20°C 3 or more ii) the potassium content of the potassium phosphate liquid fertilizer, expressed in K2O equivalents, is 48.0% w / v K2O or more, and iii) the phosphorus content of the potassium phosphate liquid fertilizer, expressed in P2O5 equivalents, is 38.0% w / v P2O5 or more.

11. Potassium phosphate liquid fertilizer according to claim 10, wherein the pH of an aqueous solution of the potassium phosphate liquid fertilizer, obtained by mixing a certain volume of the potassium phosphate liquid fertilizer with 50 times the volume of double-distilled water, measured using a pH electrode at a solution temperature of 20°C, is 7.2 or more and 7.8 or less, preferably 7.3 or more and 7.7 or less, more preferably 7.4 or more and 7.6 or less.

12. Potassium phosphate liquid fertilizer according to claim 10 or 11, wherein The potassium phosphate liquid fertilizer has a density of 1.60 g / cm³ at 20°C. 3 or more, preferably 1.61 g / cm³ 3 or more, preferably 1.62 g / cm² 3 or more, even more preferably 1.63 g / cm² 3 or more, even more preferably 1.64 g / cm² 3 or more, e.g. at least 1.65 g / cm³ 3 or at least 1.67 g / cm³ 3 exhibits.

13. Potassium phosphate liquid fertilizer according to claim 10, 11 or 12, wherein the potassium content of the potassium phosphate liquid fertilizer, expressed in KgO equivalents, is 49.0% w / v KgO or more, preferably 50.0% w / v KgO or more, more preferably 51.0% w / v K2O or more and even more preferably 52.0% w / v K2O or more.

14. Potassium phosphate liquid fertilizer according to any one of claims 10 to 13, wherein the phosphorus content of the potassium phosphate liquid fertilizer, expressed in P2O5 equivalents, is 39.0% w / v P2O5 or more, preferably 40.0% w / v P2O5 or more, more preferably 41.0% w / v P2O5 or more and even more preferably 42.0% w / v P2O5 or more.

15. Potassium phosphate liquid fertilizer according to any one of claims 10 to 14, wherein the potassium phosphate liquid fertilizer is obtainable by the method according to any one of claims 1 to 9.

16. Comprehensive fertilizer set: the potassium phosphate liquid fertilizer according to any one of claims 10 to 15; and one or more further fertilizer component(s).

17. Use of the potassium phosphate liquid fertilizer according to any one of claims 10 to 15 for the production of a ready-to-use aqueous solution of a potassium phosphate liquid fertilizer, wherein the aqueous solution of the potassium phosphate liquid fertilizer is obtained by mixing a certain volume of the potassium phosphate liquid fertilizer with water, preferably with three to 10000 times the volume of water.

18. Use of the potassium phosphate liquid fertilizer according to one of claims 10 to 15 for fertilizing potting soil, in particular a growing area, with potassium and phosphorus.

19. Method for producing a ready-to-use aqueous solution of a potassium phosphate liquid fertilizer, the method comprising: Mixing a specific volume of the potassium phosphate liquid fertilizer according to one of claims 10 to 15 with water, preferably with three to 10000 times the volume of water.

20. Method for fertilizing potting soil, in particular a growing area, with potassium and phosphorus, the method comprising: Production of a ready-to-use aqueous solution of the potassium phosphate liquid fertilizer by mixing a specific volume of the potassium phosphate liquid fertilizer according to one of claims 10 to 15 with water, preferably with three to 10,000 times the volume of water; and Applying the ready-to-use, aqueous solution of potassium phosphate liquid fertilizer to the plant soil, especially a growing area.

Images