Hard-water-resistant compound fertilizer as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of fertilizers and preparation of the fertilizers, and particularly relates to a hard-water-resistant compound fertilizer as well as a preparation method and application of the hard-water-resistant compound fertilizer. Monoammonium phosphate; humic acid having a molecular weight of less than 5000 Daltons; and a hard-water-resistant auxiliary agent. The hard-water-resistant compound fertilizer shows excellent dissolution stability in a hard water environment, can be completely dissolved in a high-hardness water environment of 30-50 DEG C, does not generate any flocculation or precipitation, has the advantages of being suitable for high-tower production, high in nutrient content, capable of improving the organic matter level in soil and the nitrogen fertilizer utilization rate and the like, and has a wide application prospect. The application prospect is wide.

Description

Technical Field

[0001] This invention belongs to the field of fertilizer and its preparation technology, specifically relating to hard water resistant compound fertilizer and its preparation method and application. Background Technology

[0002] Currently, to achieve rapid nutrient supply, high-tower melt granulation technology is commonly used to produce fully water-soluble compound fertilizers, with the addition of mineral-derived humic acid and other organic matter to enhance soil fertility. However, during the application of water-soluble fertilizers, especially fully water-soluble organic-inorganic fertilizers, it has been found that the groundwater used to dissolve the fertilizer is typically hard, and the calcium (Ca) in the hard water... 2+ ), magnesium (Mg) 2+ ) ions readily react with phosphate ions (PO4) in fertilizers 3- / HPO4 2- Combined with organic substances such as macromolecular humic acid, it forms insoluble precipitates (such as calcium phosphate and calcium sulfate) or flocculents, which significantly slows down the fertilizer dissolution rate and may even cause stratification or flocculation. Flocculation and precipitation can clog nozzles, drip irrigation tapes or filters, affecting fertilization efficiency. At the same time, the nutrients in the precipitate cannot be absorbed by crops, leading to a decrease in fertilizer effectiveness.

[0003] Currently, commercially available mineral-derived humic acid is typically produced by reacting humic acid with alkaline substances such as potassium hydroxide / sodium hydroxide to obtain humate salts with good water solubility. However, the humate salts obtained by this process have a large molecular weight and contain a large amount of poorly water-soluble macromolecular humic acid. Humic acid promotes the formation of soil aggregates through its slightly acidic characteristics and cation exchange capacity. Furthermore, its monovalent salts are soluble, while its divalent and trivalent salts are insoluble. Specifically, commercially available mineral-derived humic acid, when dissolved in water, ionizes to produce humate anions (R-COO-). - ) and potassium (K + ) or sodium (Na) + ) ions, and when hard water such as groundwater is used to dissolve fertilizers containing this type of humic acid, the calcium ions (Ca) in the water 2+ ), magnesium ions (Mg 2+ It will strongly bind with humate anions, replacing the potassium and sodium ions that were originally bound to it, forming large molecular complexes such as calcium humate and magnesium humate, which have very poor water solubility, thus causing flocculation or precipitation.

[0004] Therefore, there is an urgent need to develop a hard water resistant compound fertilizer that can effectively solve the hard water flocculation problem, while also having the advantages of being adaptable to high-tower production, maintaining full water solubility, high nutrient content, and improving the organic matter level and nitrogen fertilizer utilization rate in the soil. Summary of the Invention

[0005] This invention aims to address at least one of the technical problems existing in the prior art, particularly the issue of flocculation or precipitation in water-soluble compound fertilizers dissolved in hard water. To this end, this invention provides a hard water-resistant compound fertilizer, its preparation method, and its applications. The hard water-resistant compound fertilizer of this invention exhibits excellent solubility stability in hard water environments, completely dissolving in water with a hardness of 30°~50° without any flocculation or precipitation. Simultaneously, this compound fertilizer has advantages such as adaptability to high-tower production, high nutrient content, and the ability to improve soil organic matter levels and nitrogen fertilizer utilization, showing broad application prospects.

[0006] In a first aspect, the present invention provides a hard water resistant compound fertilizer. According to an embodiment of the present invention, the hard water resistant compound fertilizer comprises the following components: urea; monoammonium phosphate; humic acid with a molecular weight < 5000 Daltons; and a hard water resistant adjuvant. The hard water resistant compound fertilizer according to the embodiment of the present invention can still achieve rapid and complete dissolution under hard water conditions of up to 30°~50°, and maintain a clear and transparent state for a long time without any flocculation or precipitation, thereby completely solving the key problem of easy flocculation or precipitation of traditional humic acid-containing fertilizers in hard water applications.

[0007] According to embodiments of the present invention, the above-mentioned hard water resistant compound fertilizer may also have at least one of the following additional technical features: According to an embodiment of the present invention, the water-hardening-resistant compound fertilizer further includes auxiliary materials, which include trace elements and / or inhibitors.

[0008] According to an embodiment of the present invention, the trace elements include medium elements and / or trace elements.

[0009] According to an embodiment of the present invention, the medium-quantity element includes one or more of calcium, magnesium, and sulfur.

[0010] According to embodiments of the present invention, the trace elements include one or more of iron, manganese, zinc, copper, and boron.

[0011] According to an embodiment of the present invention, the inhibitor is a nitration inhibitor.

[0012] According to an embodiment of the present invention, the nitrification inhibitor is DMPSA and / or DMPP.

[0013] According to an embodiment of the present invention, the humic acid with a molecular weight of <5000 Daltons is obtained by an electrodialysis process.

[0014] According to an embodiment of the present invention, the humic acid is of mineral origin.

[0015] According to embodiments of the present invention, the hard water resistant additive includes one or more of the following: disodium lauryl sulfosuccinate, disodium fatty alcohol polyoxyethylene ether sulfosuccinate, disodium monoethanolamide sulfosuccinate, potassium monododecyl phosphate, potassium lauryl ether phosphate, ammonium fatty alcohol polyoxyethylene ether sulfate, and disodium lauryl diacetate.

[0016] According to an embodiment of the present invention, the mass ratio of the urea, the monoammonium phosphate, the humic acid with a molecular weight of <5000 Daltons, and the hard water resistance agent is (35~70):(8~30):(7~20):(0.1~0.5).

[0017] According to an embodiment of the present invention, in the hard water resistant compound fertilizer, the mass ratio of the auxiliary materials is 0.5~1.5%.

[0018] According to an embodiment of the present invention, in the excipients, the mass ratio of the trace elements to the inhibitor is (6~8):(2~4).

[0019] According to an embodiment of the present invention, the water-hardening resistant compound fertilizer further includes a potassium source.

[0020] According to an embodiment of the present invention, the potassium source includes potassium chloride and / or potassium sulfate.

[0021] According to an embodiment of the present invention, the mass ratio of the urea, the potassium chloride, the potassium sulfate, the monoammonium phosphate, the humic acid with a molecular weight <5000 Daltons, and the hard water resistant agent is (35~70):(1~5):(10~40):(8~30):(7~20):(0.1~0.5).

[0022] In a second aspect, the present invention provides a method for preparing the water-hardening-resistant compound fertilizer described in the first aspect. According to an embodiment of the present invention, the method includes the following steps: S1: heating and melting urea to obtain a melt; S2: adding monoammonium phosphate, humic acid with a molecular weight <5000 Daltons, and a water-hardening-resistant additive to the melt, and mixing to obtain a mixed liquid; S3: subjecting the mixed liquid to solidification and post-treatment to obtain the water-hardening-resistant compound fertilizer. The method according to the embodiment of the present invention successfully achieves large-scale and stable production of the water-hardening-resistant compound fertilizer.

[0023] According to embodiments of the present invention, the above method may further include at least one of the following additional technical features: According to an embodiment of the present invention, in step S2, excipients may also be added, the excipients including trace elements and / or inhibitors.

[0024] According to an embodiment of the present invention, a potassium source may also be added in step S1.

[0025] According to an embodiment of the present invention, the potassium source includes potassium chloride and / or potassium sulfate.

[0026] According to an embodiment of the present invention, the residence time of the monoammonium phosphate in the melt is ≤10 min.

[0027] According to an embodiment of the present invention, the temperature of the mixing process is 100~115°C.

[0028] According to an embodiment of the present invention, the temperature of the heating and melting treatment is 100~125°C.

[0029] According to an embodiment of the present invention, the anti-caking agent used for coating in the post-treatment is a fully water-soluble anti-caking agent.

[0030] According to an embodiment of the present invention, in step S2, the humic acid with a molecular weight <5000 Daltons is obtained by an electrodialysis apparatus.

[0031] According to a preferred embodiment of the present invention, the electrodialysis device uses a double-layer dialysis membrane, which is composed of an anion exchange membrane and a dialysis membrane.

[0032] In a third aspect of the invention, the invention proposes the application of the hard water resistant compound fertilizer described in the first aspect in hard water irrigation fertilization.

[0033] Those skilled in the art will understand that the features and advantages described above for hard water resistant compound fertilizers also apply to this application, and will not be repeated here.

[0034] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0035] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which: Figure 1 This is a schematic diagram illustrating the process principle for preparing humic acid with a molecular weight <5000 Daltons by electrodialysis according to the present invention. Figure 2 The images show the actual dissolution comparison of fertilizer slurry with different melting times in Comparative Example 1 of the present invention. From left to right, they are actual dissolution comparisons of fertilizer slurry with melting time of 10 min, 20 min, and 30 min. Detailed Implementation

[0036] The embodiments of the present invention are described in detail below. The embodiments described below are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0037] It should be noted that the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. Furthermore, in the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0038] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0039] In this document, the terms “comprising” or “including” are open-ended expressions, meaning that they include the contents specified in this invention, but do not exclude other aspects.

[0040] In this document, the terms “optionally,” “optionally,” or “optionally” generally refer to an event or condition that may, but may not, occur, and the description includes both cases in which the event or condition occurs and cases in which the event or condition does not occur.

[0041] Terms and Definitions In this paper, the term "hard water adjuvant" refers to a class of surfactants or chelating agents that can prevent or reduce the formation of insoluble precipitates or flocs from fertilizer components in hard water.

[0042] In this paper, the term "humic acid with a molecular weight of <5000 Daltons" refers to small-molecule humic acid obtained by separation and purification through processes such as electrodialysis, which has higher water solubility and hard water stability.

[0043] In this document, the term "micronutrients" refers to micronutrients or trace elements essential for plant growth, which are added to the hard water resistant compound fertilizer of this invention in the form of soluble salts, chelates, or complexes.

[0044] In this article, the term "inhibitor" refers to a formulation used to delay the conversion of ammonium nitrogen to nitrate nitrogen in order to improve nitrogen fertilizer utilization, such as nitrification inhibitors (including but not limited to DMPP, DMPSA, etc.).

[0045] In this article, the term "fully water-soluble anti-caking agent" refers to a coating material that can be completely dissolved in water and prevent fertilizer granules from clumping.

[0046] In this article, the term "hard water" refers to water with a high concentration of calcium and magnesium ions and a hardness of not less than 30°, such as well water and deep well water. This type of water source is usually the most common type of water source for agricultural irrigation and has the most prominent hardness problem.

[0047] In this article, the term "Mannheim process" refers to a mature industrial method for producing potassium sulfate by using potassium chloride and concentrated sulfuric acid as raw materials and carrying out a metathesis reaction in a high-temperature (typically above 500°C) Mannheim furnace. This process yields potassium sulfate products with high purity (typically ≥52% K₂O) and high chloride ion (Cl₂) content. - The content of potassium sulfate is extremely low (usually ≤1.5%), and its physical form is mostly powder. It has excellent water solubility. The potassium sulfate prepared by this process is particularly suitable for the hard water resistant compound fertilizer of this invention.

[0048] In this document, the term "industrial grade" refers to raw materials that meet Chinese national, industry, or recognized industrial product standards, and whose purity, active ingredient content, and impurity limits meet the basic requirements for large-scale industrial fertilizer production.

[0049] In this paper, the term "total acid content" refers to the total amount of ionizable hydrogen ions (H+) per unit mass of humic acid sample. + The total amount of functional groups of humic acid, expressed in millimoles per gram (mmol / g), reflects the overall abundance of acidic functional groups such as carboxyl groups (-COOH) and phenolic hydroxyl groups (-OH) in humic acid samples. It is a key indicator for measuring the chemical activity, ion exchange capacity, and potential for interaction with metal ions of humic acid.

[0050] In this paper, the term "phenolic hydroxyl content" refers to the number of phenolic hydroxyl (-OH) functional groups contained in a unit mass of humic acid sample, expressed in millimoles per gram (mmol / g). As an important redox and complexation site in humic acid molecules, the phenolic hydroxyl group directly affects its antioxidant capacity and complexation strength with polyvalent metal ions. In this invention, optimizing the phenolic hydroxyl content level helps to balance the chemical activity and antiflocculation performance of humic acid.

[0051] In this paper, the term "E4 / E6" refers to the ratio of the absorbance of a humic acid sample at two specific wavelengths in the visible light region, namely 465 nm (E4) and 665 nm (E6). This index is closely related to the molecular size, degree of aromatization, and degree of molecular condensation of humic acid. When the E4 / E6 ratio is high, it indicates that the sample has a lower molecular weight, a higher content of aliphatic chains, and a simpler structure (such as fulvic acid characteristics). In the embodiments of this invention, this index is also one of the intrinsic structural characteristics for evaluating whether a sample has excellent water solubility and hard water resistance.

[0052] Hard water resistant compound fertilizer This invention proposes a hard water resistant compound fertilizer. According to an embodiment of the invention, the hard water resistant compound fertilizer comprises the following components: urea; monoammonium phosphate; humic acid with a molecular weight <5000 Daltons; and a hard water resistant adjuvant. The hard water resistant compound fertilizer of this invention can still achieve rapid and complete dissolution under hard water conditions of up to 30°~50°, and remain clear and transparent for a long time without any flocculation or precipitation, thus completely solving the key problem of easy flocculation or precipitation of traditional humic acid-containing fertilizers in hard water applications.

[0053] According to an embodiment of the present invention, the monoammonium phosphate is industrial grade (i.e., total nutrient content ≥72%).

[0054] According to an embodiment of the present invention, the water-hardening-resistant compound fertilizer further includes auxiliary materials, which include micronutrients and / or inhibitors. Thus, while ensuring the core water-hardening-resistant function, the nutrient composition is further enriched, achieving a complete nutrient supply of micronutrients and organic matter; the addition of inhibitors also extends the fertilizer's effective period, thereby meeting the diverse growth needs of crops.

[0055] According to an embodiment of the present invention, the potassium sulfate is potassium sulfate produced by the Mannheim process. Therefore, the addition of potassium sulfate prepared by this process, due to its extremely high purity and excellent water solubility, can effectively improve the quality (uniformity, etc.) of the hard water resistant compound fertilizer of the present invention.

[0056] According to an embodiment of the present invention, the micronutrients include medium-level elements and / or trace elements. This further enhances the nutritional value of the water-hardening compound fertilizer of the present invention.

[0057] According to an embodiment of the present invention, the medium-quantity element includes one or more of calcium, magnesium, and sulfur.

[0058] According to embodiments of the present invention, the trace elements include one or more of iron, manganese, zinc, copper, and boron.

[0059] It should be noted that in the water-hardening compound fertilizer described in this invention, the specific types, proportions, and combinations of the auxiliary materials can be adjusted and optimized according to actual application needs, and these adjustments and selections of auxiliary materials are all within the scope of protection of this invention.

[0060] According to an embodiment of the present invention, the inhibitor is a nitrification inhibitor. Therefore, by adding a nitrification inhibitor, the microbial conversion of ammonium nitrogen to nitrate nitrogen in the soil is effectively inhibited, thereby significantly reducing the risk of nitrogen leaching in the form of nitrate or denitrification gaseous loss, and thus improving fertilizer utilization from the source.

[0061] According to an embodiment of the present invention, the nitrification inhibitor is DMPSA and / or DMPP.

[0062] According to an embodiment of the present invention, the humic acid with a molecular weight <5000 Daltons is prepared by an electrodialysis process. Therefore, under the electrodialysis process, small-molecule fulvic acid components rich in functional groups such as carboxyl and phenolic hydroxyl groups can be efficiently separated, further ensuring the hard water resistance quality of the humic acid raw material.

[0063] According to an embodiment of the present invention, the humic acid with a molecular weight <5000 Daltons is prepared by an electrodialysis device, wherein the electrodialysis device uses a double-layer dialysis membrane, the double-layer dialysis membrane being composed of an anion exchange membrane and a dialysis membrane.

[0064] In this paper, the term "humic acid with a molecular weight < 5000 Daltons" refers to humic acid components with a molecular weight < 5000 Daltons obtained by separating and purifying natural humic acid through physical or chemical methods (such as electrodialysis, membrane separation, etc.). This component has fulvic acid as the main active substance, its molecular structure is relatively simple, and it is rich in hydrophilic functional groups such as carboxyl groups (-COOH) and phenolic hydroxyl groups (-OH), and has excellent water solubility. Compared with untreated ordinary humic acid or commercially available potassium / sodium humate, this component has a small molecular weight and low steric hindrance, which can effectively avoid the formation of flocs or precipitates by combining with calcium and magnesium ions in hard water, thereby giving the hard water resistant compound fertilizer of this invention stable hard water resistance performance.

[0065] Taking the process of preparing humic acid with a molecular weight of <5000 Daltons by electrodialysis as an example (see details) Figure 1 The principle of electrodialysis is explained as follows: The electrodialysis device mainly consists of positive and negative electrodes, anion and cation exchange membranes located between the electrodes, and a dialysis membrane. For example, a commercially available potassium humate solution is used as the raw material. After electricity is applied, potassium ions (K+) ionize in the solution. + Under the influence of an electric field, the ions migrate towards the cathode and pass through the cation exchange membrane into another compartment, where they react with hydroxide ions (OH-) generated by water electrolysis. - The combination of these compounds forms potassium hydroxide (KOH) as a byproduct, while simultaneously, humic acid anions (HA) are also produced.- ) migrate towards the anode; among them, small molecule humic acid anions (mainly fulvic acid) with a molecular weight <5000 Daltons can successfully pass through the composite membrane layer composed of anion exchange membrane and dialysis membrane, enter a specific receiving chamber, and react with hydrogen ions (H+) generated there. + The humic acid is converted back into a solution of small-molecule humic acid (fulvic acid) with active functional groups (-COOH, -OH). Meanwhile, the larger humic acid anions (mainly humic acid) in the raw material are effectively retained in the original solution chamber because their molecular size exceeds the cutoff range of the dialysis membrane. This achieves precise separation from the small-molecule components, enabling the preparation of high-purity small-molecule humic acid raw materials (molecular weight < 5000 Daltons). Furthermore, this separation and purification process removes the poorly water-soluble large-molecule humic acid while retaining the small-molecule fulvic acid. Fulvic acid is rich in carboxylic acid (-COOH) and phenolic hydroxyl (-OH) functional groups, thus greatly improving the solubility of the solid humic acid raw material in water and its resistance to hard water.

[0066] For example, the electrodialysis device uses a double-layer dialysis membrane, which is composed of an anion exchange membrane and a dialysis membrane.

[0067] It should be noted that the preparation method of humic acid with a molecular weight of <5000 Daltons in the hard water resistant compound fertilizer of the present invention is not limited to electrodialysis. Any other physical, chemical or biological method (including but not limited to membrane separation, gradient acid precipitation, specific oxidative degradation, etc.) that can effectively obtain and control the molecular weight of humic acid within the range of <5000 Daltons shall be protected by the present invention.

[0068] According to an embodiment of the present invention, the humic acid is mineral-derived. Therefore, the combined application of mineral-derived humic acid yields better results.

[0069] According to embodiments of the present invention, the anti-hard water adjuvant includes one or more of the following: disodium lauryl sulfosuccinate, disodium fatty alcohol polyoxyethylene ether sulfosuccinate, disodium monoethanolamide sulfosuccinate, potassium monododecyl phosphate, potassium lauryl ether phosphate, ammonium fatty alcohol polyoxyethylene ether sulfate, and disodium lauryl diacetate. Thus, by adding the anti-hard water adjuvant, the adjuvant effectively shields or isolates calcium and magnesium ions in hard water, preventing them from reacting with the effective components of the fertilizer to form a precipitation reaction. Furthermore, it synergizes with other components in the anti-hard water compound fertilizer of the present invention to further enhance the anti-hard water capability.

[0070] According to an embodiment of the present invention, the mass ratio of urea, monoammonium phosphate, humic acid with a molecular weight <5000 Daltons, and the anti-hard water agent is (35~70):(8~30):(7~20):(0.1~0.5). Thus, by optimizing and controlling the ratio of key components, the nutrient content, process feasibility (melting and granulation performance), and anti-hard water effect are further balanced. For example, the mass ratios of urea, monoammonium phosphate, humic acid with a molecular weight <5000 Daltons, and the anti-hard water agent are 35:8:7:0.1, 40:8:7:0.1, 50:8:7:0.1, 60:8:7:0.1, 70:8:7:0.1, 35:10:7:0.1, 35:15:7:0.1, and 35:20: 7:0.1, 35:25:7:0.1, 35:30:7:0.1, 35:8:10:0.1, 35:8:15:0.1, 35:8:20:0.1, 35:8:7:0.2, 35:8:7:0.3, 35:8:7:0.4, 35:8:7:0.5, preferably (35~60):(8~27):(10~20):(0.15~0.4), more preferably (35~50):(8~25):(10~15):(0.1~0.5).

[0071] According to an embodiment of the present invention, the mass percentage of the auxiliary materials in the hard water resistant compound fertilizer is 0.5-1.5%. Therefore, by optimizing and controlling the proportion of auxiliary materials, the hard water resistant compound fertilizer is ensured to meet the relevant national standards for total nutrients and single nutrients, while avoiding potential interference with the core hard water resistant system or negative impacts on the product's physical properties (such as hardness and hygroscopicity) due to excessive addition of auxiliary materials. For example, the mass percentage of the auxiliary materials is 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 1.1%, 1.2%, 1.3%, 1.4%, or 1.5%, preferably 0.5-1.2%, and more preferably 0.8-1.0%.

[0072] According to an embodiment of the present invention, in the excipients, the mass ratio of the micronutrients to the inhibitor is (6~8):(2~4). This further optimizes the application effect of the water-hardening-resistant compound fertilizer; exemplaryly, the mass ratio of the micronutrients to the inhibitor is 6:2, 7:2, 8:2, 6:3, 6:4, 6:2, 7:3, preferably (6~7):(1~2), and more preferably (3~4):(1~2).

[0073] According to an embodiment of the present invention, the water-hardening resistant compound fertilizer further includes a potassium source.

[0074] According to an embodiment of the present invention, the potassium source includes potassium chloride and / or potassium sulfate.

[0075] According to an embodiment of the present invention, the mass ratio of the urea, the potassium chloride, the potassium sulfate, the monoammonium phosphate, the humic acid with a molecular weight <5000 Daltons, and the hard water resistant agent is (35~70):(1~5):(10~40):(8~30):(7~20):(0.1~0.5). Therefore, the application effect of the hard water resistant compound fertilizer is further optimized; for example, the mass ratio of urea, potassium chloride, potassium sulfate, monoammonium phosphate, humic acid with a molecular weight <5000 Daltons, and the hard water resistant adjuvant is 35:1:10:8:7:0.1, 40:1:10:8:7:0.1, 50:1:10:8:7:0.1, 60:1:10:8:7:0.1, 35:2:10:8:7:0.1, 35:3:10:8:7:0.1, 35:4:10:8:7:0.1, 35:5:10:8:7:0.1, 35:1:20:8:7:0.1, 35:1:30:8:7:0.1, 35:1:40:8:7: 0.1, 35:1:10:10:7:0.1, 35:1:10:20:7:0.1, 35:1:10:30:7:0.1, 35:1:10:8:10:0.1, 35:1:10:8:20:0.1, 35:1:10:8:7:0.2, 35:1:10:8:7:0.3, 35:1: 10:8:7:0.4, 35:1:10:8:7:0.5, preferably (35~60):(1~4):(10~35):(8~27):(10~20):(0.15~0.4), more preferably (35~50):(2~4):(10~25):(8~25):(10~15):(0.1~0.5).

[0076] method This invention proposes a method for preparing the aforementioned water-hardening-resistant compound fertilizer. According to an embodiment of the invention, the method includes the following steps: S1: heating and melting urea to obtain a melt; S2: adding monoammonium phosphate, humic acid with a molecular weight <5000 Daltons, and a water-hardening-resistant additive to the melt, and mixing to obtain a mixed liquid; S3: subjecting the mixed liquid to solidification and post-treatment to obtain the water-hardening-resistant compound fertilizer. The method according to the embodiment of the invention successfully achieves large-scale and stable production of the water-hardening-resistant compound fertilizer.

[0077] According to an embodiment of the present invention, in step S2, excipients may also be added, including trace elements and / or inhibitors. Thus, while ensuring the core hard water resistance function of the formulation, different target requirements can be met by adjusting the excipient formulation.

[0078] According to an embodiment of the present invention, a potassium source may also be added in step S1.

[0079] According to an embodiment of the present invention, the potassium source includes potassium chloride and / or potassium sulfate.

[0080] According to an embodiment of the present invention, the residence time of the monoammonium phosphate in the melt is ≤10 min. Therefore, by strictly controlling the residence time of the monoammonium phosphate in the melt, it is possible to minimize its reaction with urea at high temperatures to generate a large amount of phosphate ions (such as H₂PO₄) that readily combine with calcium and magnesium ions in hard water. 2- and PO4 3- This cuts off the main pathway for the formation of insoluble precipitates such as calcium phosphate at the source, thereby further improving the hard water resistance performance of the prepared hard water resistant compound fertilizer.

[0081] According to an embodiment of the present invention, the mixing temperature is 100~115℃. Thus, while ensuring thorough mixing of all raw materials, by jointly and strictly controlling the temperature conditions and residence time of monoammonium phosphate in the melt, the main pathway for the formation of insoluble precipitates such as calcium phosphate is cut off at the source, further improving the hard water resistance performance of the prepared hard water resistant compound fertilizer. Exemplarily, the mixing temperature is 100℃, 101℃, 102℃, 103℃, 104℃, 105℃, 106℃, 107℃, 108℃, 109℃, 110℃, 111℃, 112℃, 113℃, 114℃, or 115℃, preferably 105~115℃, and more preferably 105~110℃.

[0082] According to an embodiment of the present invention, the temperature of the heating and melting treatment is 100~125℃. Thus, by optimizing and controlling the temperature of the heating and melting treatment, it is ensured that urea and potassium chloride are fully melted and form a uniform and stable eutectic, providing a base carrier with good fluidity for subsequent steps, while preventing excessive pyrolysis of urea to produce harmful substances such as biuret. Exemplarily, the temperature of the heating and melting treatment is 100℃, 101℃, 102℃, 103℃, 104℃, 105℃, 106℃, 107℃, 108℃, 109℃, 110℃, 111℃, 112℃, 113℃, 114℃, 115℃, 116℃, 117℃, 118℃, 119℃, 120℃, 121℃, 122℃, 123℃, 124℃, or 125℃, preferably 110~125℃, and more preferably 115~120℃.

[0083] According to an embodiment of the present invention, the anti-caking agent used for coating in the post-treatment is a fully water-soluble anti-caking agent. Therefore, using a fully water-soluble anti-caking agent in the post-treatment process can form a hydrophilic film on the surface of the fertilizer granules, effectively preventing the prepared hard water resistant compound fertilizer from absorbing moisture and clumping during storage and transportation, thus maintaining its good looseness and ease of application.

[0084] In this document, the term "solidification molding process" refers to the physical processing of transforming the mixed liquid into solid particles. This process aims to form fertilizer particles with specific particle size, strength, and shape by removing moisture from the liquid and / or cooling and solidifying it. Specific implementations include, but are not limited to, various methods such as high-tower melt spraying granulation, spray drying molding, rotary drum granulation, or fluidized bed granulation. For example, in an embodiment of the present invention, the mixed liquid is sprayed from the top of the granulation tower and falls, exchanging heat and dehumidifying with a certain temperature gas rising from the bottom of the tower during the falling process to ensure that the moisture content of the particles is reduced to below 0.8%. Then, the particles falling to the bottom of the tower are cooled and screened.

[0085] According to an embodiment of the present invention, in step S2, the humic acid with a molecular weight <5000 Daltons is obtained by an electrodialysis apparatus.

[0086] According to a preferred embodiment of the present invention, the electrodialysis device uses a double-layer dialysis membrane, which is composed of an anion exchange membrane and a dialysis membrane.

[0087] application This invention proposes the application of the aforementioned hard water resistant compound fertilizer in hard water irrigation fertilization.

[0088] Those skilled in the art will understand that the features and advantages described above for hard water resistant compound fertilizers also apply to this application, and will not be repeated here.

[0089] The present invention will be explained below with reference to embodiments. Those skilled in the art will understand that the following embodiments are for illustrative purposes only and should not be considered as limiting the scope of the invention. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in the field or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be obtained commercially.

[0090] Example 1: Preparation of small molecule mineral-derived humic acid Small molecule mineral humic acid was prepared using an electrodialysis process. The electrodialysis device and dialysis membrane were purchased from Weifang Tianwei Membrane Technology Co., Ltd. The specific steps are as follows: (1) Pre-treat the dialysis membrane with a molecular weight cutoff of 5000 Daltons and install it into the electrodialysis device. The pre-treatment involves placing the dialysis membrane with a molecular weight cutoff of 5000 Daltons in deionized water, heating and boiling it for about 30 minutes, then immersing it naturally and cooling it to room temperature, and then installing it on the outside of the anion membrane of the electrodialysis device in a moist state.

[0091] (2) Prepare a 30% aqueous solution of commercially available fully water-soluble mineral potassium fulvate (purchased from Xinjiang Black Ecological, product number DD-potassium fulvate). Then place the feed pump inlet and outlet of the feed chamber of the electrodialysis device into the mineral potassium fulvate aqueous solution. Place the feed pump inlet and outlet of the feed pump of the acid chamber and alkali chamber of the electrodialysis device into the corresponding acid and alkali storage tanks respectively (the solution is pure water containing a small amount of potassium chloride). (3) Turn on the feed pump of the electrodialysis device, and then turn on the rectifier of the electrodialysis device to convert 220 V AC power into DC power; Specifically, potassium humate from mineral source will ionize in aqueous solution to form K cations and humic acid anions. The cations move towards the cathode under the action of the DC electric field, and enter the alkaline chamber of the electrodialysis device through the anode membrane (only cations can pass through), and then react with the hydroxide ions formed by the anion and cation membranes to form potassium hydroxide, which is pumped to the alkaline storage tank by the alkaline chamber pump; the humic acid anions move towards the anode under the action of the DC electric field. Humic acid with a molecular weight <5000 Daltons enters the acid chamber of the electrodialysis device through the dialysis membrane and the anion membrane (only anions can pass through), and then reacts with the hydrogen ions formed by the anion and cation membranes to form humic acid with a molecular weight less than 5000 Daltons, which is pumped to the acid storage tank by the acid chamber pump. Thus, a humic acid solution with a molecular weight <5000 Daltons is obtained. (4) The humic acid solution with a molecular weight of <5000 Daltons obtained in step (3) is dried to obtain a humic acid sample with a molecular weight of <5000 Daltons. (5) Using liquid chromatography with gel chromatography column, the molecular weight of commercially available fully water-soluble mineral potassium humate sample and humic acid solution with molecular weight <5000 Daltons (concentration of 0.1 g / L, filtered through 0.45 μm membrane) prepared in step (3) were detected. Elemental analysis, potentiometric titration and UV-Vis spectrophotometry were used to detect various parameters of the two samples. The test indicators included nitrogen content (N%), carbon content (C%), hydrogen content (H%), sulfur content (S%), total acid content (mmol / g), carboxyl content (mmol / g), phenolic hydroxyl content (ArOH, mmol / g) and E4 / E6.

[0092] Table 1 shows the comparative test results of commercially available fully water-soluble potassium humate samples and humic acid samples prepared in this invention.

[0093] Table 1. Comparative test results of commercially available fully water-soluble potassium humate samples and humic acid samples prepared in this invention.

[0094] The results showed that the molecular weight of commercially available fully water-soluble potassium fulvate samples ranged from 2,000 to 50,000 Daltons, with an average molecular weight of 9,000 Daltons. In contrast, the molecular weight of the humic acid samples prepared by electrodialysis in this invention ranged from 2,000 to 5,000 Daltons, with an average molecular weight of 3,000 Daltons. At the same time, compared with commercially available fully water-soluble potassium fulvate samples, the phenolic hydroxyl content of the humic acid samples prepared by electrodialysis in this invention was significantly increased.

[0095] Example 2: Preparation of a fully water-soluble organic-inorganic compound fertilizer resistant to hard water (1) Melting: 360 kg of urea and 40 kg of potassium chloride are added to the melting tank according to the formula ratio and heated to melt. The reaction temperature is controlled at 120°C to form a eutectic, which is then pumped to the primary mixing tank. (2) Primary mixing: In the primary mixing tank, add 240 kg of Mannheim potassium sulfate according to the proportion, keep the temperature at 115℃, and then overflow to the secondary tank; (3) Secondary mixing and granulation: 250 kg of industrial grade monoammonium phosphate, 4 kg of EDTAN-Zn, 4 kg of sodium tetraborate tetrahydrate, 1 kg of inhibitor DMPP, 1 kg of disodium lauryl iminodiacetate and 100 kg of humic acid with a molecular weight of <5000 Daltons were added to the secondary tank and the temperature was maintained at 105℃ to prepare a mixed slurry. The residence time was about 10 min. After the mixed slurry passed through the high-speed shear machine, it was sprayed and granulated from the top of the tower. The humic acid with a molecular weight of <5000 Daltons was the humic acid sample with a molecular weight of <5000 Daltons obtained by step (4) of Example 1. (4) Cooling and post-treatment: The falling particles exchange heat and dehumidify with the gas at a certain temperature rising from the bottom of the tower to ensure that the moisture content of the fertilizer particles is below 0.8%. After cooling, screening and coating (fully water-soluble anti-caking oil powder), a fully water-soluble organic-inorganic compound fertilizer resistant to hard water is prepared.

[0096] Comparative Example 1: Preparation of Fully Water-Soluble Compound Fertilizer (1) Melting: 360 kg of urea and 40 kg of potassium chloride are added to the melting tank according to the formula ratio and heated to melt. The reaction temperature is controlled at 120°C to form a eutectic, which is then pumped to the primary mixing tank. (2) Primary mixing: In the primary mixing tank, add 240 kg of Mannheim potassium sulfate according to the proportion, keep the temperature at 115℃, and then overflow to the secondary tank; (3) Secondary mixing and granulation: 250 kg of industrial grade monoammonium phosphate, 4 kg of EDTAN-Zn, 4 kg of sodium tetrahydrate octaborate and 1 kg of inhibitor DMPP were added to the secondary tank and the temperature was maintained at 105℃ to prepare a mixed slurry. The residence time was about 10 min. After the mixed slurry passed through the high-speed shear machine, it was sprayed and granulated from the top of the tower. Samples I, II and III of the slurry were taken out 10 min, 20 min and 30 min after the addition of industrial grade monoammonium phosphate, respectively. After cooling, a dissolution test was carried out (using 30° hard water, fertilizer-to-water ratio of 1:100, stirring and dissolving time of 3 min). The falling particles exchange heat and dehumidify with the rising gas at a certain temperature at the bottom of the tower to ensure that the moisture content of the fertilizer particles is below 0.8%. After cooling, sieving, and coating (with fully water-soluble anti-caking powder), fully water-soluble compound fertilizer I is prepared (its melting time is 10 min).

[0097] Comparison of actual dissolution of fertilizer slurry at different melting times is shown in the photographs. Figure 2 The statistical results of the fertilizer slurry dissolution experiment at different melting times are shown in Table 2.

[0098] Table 2 Statistical results of fertilizer slurry dissolution experiments at different melting times

[0099] The results showed that monoammonium phosphate reacts with urea to produce HPO4. 2- Or PO4 3- Substances that are prone to flocculation or precipitation by calcium and magnesium ions will cause the slurry to become slightly turbid within 20 minutes. To improve the fertilizer's resistance to hard water and ensure that the slurry does not become turbid, the reaction time of monoammonium phosphate and urea should be controlled at around 10 minutes (≤10 minutes is optimal).

[0100] Comparative Example 2: Preparation of a fully water-soluble organic-inorganic compound fertilizer (1) Melting: 360 kg of urea and 40 kg of potassium chloride are added to the melting tank according to the formula ratio and heated to melt. The reaction temperature is controlled at 120°C to form a eutectic, which is then pumped to the primary mixing tank. (2) Primary mixing: In the primary mixing tank, add 240 kg of Mannheim potassium sulfate according to the proportion, keep the temperature at 115℃, and then overflow to the secondary tank; (3) Secondary mixing and granulation: 250 kg of industrial grade monoammonium phosphate, 2 kg of EDTAN-Zn, 2 kg of sodium tetraborate tetrahydrate, 1 kg of inhibitor DMPP, 1 kg of fatty alcohol polyoxyethylene ether sulfosuccinate monoester disodium salt anti-hard water agent and 100 kg of commercially available fully water-soluble mineral potassium humate (average molecular weight of about 9000 Daltons) are added to the secondary tank. The temperature is maintained at 105℃ to prepare a mixed slurry. The residence time is about 10 min. After the mixed slurry passes through the high-speed shear machine, it is sprayed and granulated from the top of the tower. The falling particles exchange heat and dehumidify with the rising gas at a certain temperature at the bottom of the tower to ensure that the moisture content of the fertilizer particles is below 0.8%. After cooling, sieving, and coating (with water-soluble anti-caking powder), water-soluble compound fertilizer II is prepared.

[0101] Example 3: Comparison of dissolution tests of different compound fertilizers Dissolution tests were conducted on the fully water-soluble organic-inorganic compound fertilizer prepared in Example 2, the fully water-soluble compound fertilizer I prepared in Comparative Example 1, and the fully water-soluble compound fertilizer II prepared in Comparative Example 2. The specific steps are as follows: Preparation of test media: Prepare 30° hard water and 50° hard water as test media respectively.

[0102] Dissolution process: Weigh 10.0 g of each test sample fertilizer and place it in a 1 L beaker. Add 1000 mL of the corresponding hard water (fertilizer-to-water mass ratio of 1:100). Stir magnetically at 300 rpm for 3 min at room temperature of 25℃ to ensure initial full dispersion.

[0103] Observation after standing: After stirring is stopped, start timing and let it stand. Visually observe and record the state of the solution in the beaker and the precipitate at the bottom at 0 min (i.e., immediately after stirring stops), 30 min, 60 min and 120 min respectively.

[0104] The results of the dissolution test comparison of different compound fertilizers are shown in Table 3.

[0105] Table 3 Comparison of dissolution test results for different compound fertilizers

[0106] Filtration and drying: After the above samples were left to stand for 120 min, they were filtered with filter paper, dried, and the proportion of precipitated substances was determined.

[0107] The results of the dissolution tests of different compound fertilizers are shown in Table 4.

[0108] Table 4. Results of the percentage of precipitated substances in different compound fertilizers

[0109] The results showed that the fully water-soluble organic-inorganic compound fertilizer sample prepared in Example 2 did not flocculate in hard water at 30° and 50°, indicating that it had a better hard water resistance effect. However, the fully water-soluble compound fertilizer sample I prepared in Comparative Example 1 showed almost no flocculation or precipitation in hard water at 30°, but flocculation and precipitation were more obvious in hard water at 50°. This is mainly due to the HPO4 generated from the reaction of urea and monoammonium phosphate. 2- Or PO4 3- These substances can react with calcium and magnesium ions in hard water to form CaHPO4, which has poor water solubility. 2- Or Ca3(PO4)2 or MgHPO4 2- Or substances such as Mg3(PO4)2; at the same time, the fully water-soluble compound fertilizer II sample prepared in Comparative Example 2 showed little flocculation in 30° hard water, but flocculation and even precipitation occurred in 50° hard water. The main reason for this is that commercially available fully water-soluble mineral potassium fulvate contains a large amount of humic acid with a large molecular weight. As a macromolecular mixture, humic acid has a significantly higher molecular weight than fulvate. The macromolecular structure leads to large steric hindrance, making it difficult to form a stable hydrated layer with water molecules, and it is easy to aggregate in hard water due to intermolecular entanglement. Furthermore, humic acid has a high degree of aromatic condensation and a relatively small number of oxygen-containing functional groups (such as carboxyl groups and phenolic hydroxyl groups). Calcium and magnesium ions (divalent cations) in hard water can undergo complexation reactions with negatively charged groups such as carboxyl groups and phenolic hydroxyl groups in humic acid molecules to form a "humic acid-metal ion-humic acid" bridging structure. This bridging effect leads to the aggregation of humic acid molecules, forming insoluble flocculants. As the concentration of calcium and magnesium ions increases, the bridging structure further expands, eventually forming visible flocculent precipitates (such as calcium magnesium humate).

[0110] The above results demonstrate that using small-molecule humic acid raw materials (<5000 Daltons) to eliminate organic matter bridging flocculation and strictly controlling the reaction time of monoammonium phosphate to inhibit phosphate precipitation can synergistically solve the problem of flocculation and precipitation of compound fertilizer in hard water, thereby preparing compound fertilizer with excellent hard water resistance. In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0111] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A hard water resistant compound fertilizer, characterized in that, The water-hardening resistant compound fertilizer comprises the following components: Urea; Monoammonium phosphate; Humic acid with a molecular weight of less than 5000 Daltons; Hard water resistant additives.

2. The water-hardening resistant compound fertilizer according to claim 1, characterized in that, The water-hardening-resistant compound fertilizer also includes auxiliary materials, which include micronutrients and / or inhibitors; Optionally, the trace elements include medium elements and / or trace elements; Optionally, the medium-quantity element includes one or more of calcium, magnesium, and sulfur; Optionally, the trace elements include one or more of iron, manganese, zinc, copper, and boron; Optionally, the inhibitor is a nitration inhibitor; Optionally, the nitrification inhibitor is DMPSA and / or DMPP.

3. The water-hardening resistant compound fertilizer according to claim 1, characterized in that, The humic acid with a molecular weight of <5000 Daltons was prepared by an electrodialysis process. Optionally, the humic acid is of mineral origin; Optionally, the hard water resistance additive includes one or more of the following: disodium lauryl sulfosuccinate, disodium fatty alcohol polyoxyethylene ether sulfosuccinate, disodium monoethanolamide sulfosuccinate, potassium monododecyl phosphate, potassium lauryl ether phosphate, ammonium fatty alcohol polyoxyethylene ether sulfate, and disodium lauryl diacetate.

4. The water-hardening-resistant compound fertilizer according to any one of claims 1 to 3, characterized in that, The mass ratio of the urea, the monoammonium phosphate, the humic acid with a molecular weight <5000 Daltons, and the anti-hard water agent is (35~70):(8~30):(7~20):(0.1~0.5). Optionally, in the hard water resistant compound fertilizer, the mass percentage of the auxiliary materials is 0.5% to 1.5%; Optionally, in the excipients, the mass ratio of the trace elements to the inhibitor is (6~8):(2~4).

5. The hard water resistant compound fertilizer according to any one of claims 1 to 4, characterized in that, The hard water resistant compound fertilizer also includes a potassium source; Optionally, the potassium source includes potassium chloride and / or potassium sulfate; Preferably, the mass ratio of the urea, potassium chloride, potassium sulfate, monoammonium phosphate, humic acid with a molecular weight <5000 Daltons, and the hard water resistant agent is (35~70):(1~5):(10~40):(8~30):(7~20):(0.1~0.5).

6. A method for preparing the hard water resistant compound fertilizer according to any one of claims 1 to 5, characterized in that, The method includes the following steps: S1: Heat and melt urea to obtain a melt; S2: Add monoammonium phosphate, humic acid with a molecular weight of <5000 Daltons, and an anti-hard water agent to the melt, and mix them to obtain a mixed liquid. S3: The mixture is solidified and post-treated to obtain the hard water resistant compound fertilizer.

7. The method according to claim 6, characterized in that, In step S2, excipients may also be added, including trace elements and / or inhibitors; Optionally, a potassium source may also be added in step S1; Optionally, the potassium source includes potassium chloride and / or potassium sulfate; Optionally, the residence time of the monoammonium phosphate in the melt is ≤10 min; Optionally, the temperature of the mixing process is 100~115°C.

8. The method according to claim 6, characterized in that, The temperature for the heating and melting treatment is 100~125℃; Optionally, the anti-caking agent used for coating in the post-treatment is a fully water-soluble anti-caking agent.

9. The method according to claim 6, characterized in that, In step S2, the humic acid with a molecular weight <5000 Daltons is obtained by an electrodialysis device; Preferably, the electrodialysis device uses a double-layer dialysis membrane, which is composed of an anion exchange membrane and a dialysis membrane.

10. The application of the hard water resistant compound fertilizer according to any one of claims 1 to 5 in hard water irrigation fertilization.

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