The use method of the reaction extruded granular solid fertilizer which is rapidly changed into slow-release liquid type and suspended liquid fertilizer

Abstract

The application belongs to the technical field of slow / controlled release chemical fertilizer, and particularly relates to a use method of reaction extrusion granular solid fertilizer which can become slow-release liquid fertilizer of a clear liquid type and a suspension type, when the granular solid fertilizer is mixed with water at a ratio of 1 kg: 200-300 L, stirring is carried out for 2-12 minutes, until the granular solid fertilizer is dissolved in water to become slow-release liquid fertilizer of the clear liquid type; when the granular solid fertilizer is mixed with water at a ratio of 1 kg: 1-5 L, stirring is carried out for 10-20 minutes, and the granular solid fertilizer becomes slow-release liquid fertilizer of the suspension type. The granular solid fertilizer has the advantages of high stability of powder liquid fertilizer, convenience in carrying and storage, relatively low cost, wide applicability, and simultaneously solves the problems of slow dissolution speed, easy generation of residues, need of special equipment, easy moisture absorption and caking, and dust pollution risk.

Description

Technical Field

[0001] This invention belongs to the field of slow / controlled release fertilizer technology, specifically a method for using reactive extrusion granular solid fertilizer that can quickly become slow-release clear liquid and suspension liquid fertilizers. Background Technology

[0002] The low nutrient utilization efficiency of traditional fertilizers leads to resource waste and environmental pollution, thus slow / controlled-release fertilizers have emerged. Liquid fertilizers have gained widespread attention due to their advantages such as rapid absorption, flexible formulation, and environmental friendliness, especially with the rapid development of integrated water / fertilizer technology. However, liquid fertilizers also have many disadvantages, the most significant being their high transportation and storage costs. Specifically: ① Low concentration of effective ingredients: The concentration of effective ingredients in liquid fertilizer is usually lower than that in solid fertilizer. This means that when transporting the same amount of nutrients, liquid fertilizer requires a larger volume, and therefore, the transportation cost is higher.

[0003] ② Fragile Packaging: Liquid fertilizers are mostly packaged in plastic containers, which are prone to leakage or container breakage during long-distance transportation, resulting in waste and additional costs. In contrast, solid water-soluble fertilizers can be packed in woven bags, making transportation more convenient and safer.

[0004] Currently, solid water-soluble fertilizers, both domestically and internationally, are mainly powder-based liquid fertilizers. Their specific advantages include: ① High stability: It is not easily affected by environmental conditions such as temperature and humidity during storage and transportation, and is not easily deteriorated or chemically reacted.

[0005] ② Easy to carry and store: It is in powder form, small in size and light in weight, making it easy to package and transport over long distances, and it is not easy to leak.

[0006] ③ Relatively low cost: The production process is usually simpler than that of liquid fertilizer, and the production and purchase costs may be lower.

[0007] ④ Wide applicability.

[0008] The disadvantages of powdered liquid fertilizer are: ① Solubility and Usage Issues: A) Slow Dissolution: Powder dissolves slowly in water and requires thorough stirring; otherwise, it may not dissolve completely, leading to delayed fertilizer effect or uneven nutrient absorption. B) Prone to Residue: Incompletely dissolved powder may form sediment, clogging irrigation equipment such as drip irrigation heads and sprinklers. C) Requires Specialized Equipment: Large-scale use requires specialized dissolution and stirring equipment, increasing operational complexity.

[0009] ② Transportation and Storage Issues: A) Moisture Absorption and Clumping: Powders are hygroscopic and easily clump and deteriorate if stored improperly (e.g., in humid environments), affecting fertilizer efficacy and application. B) Large Packaging Size: Powder packaging is typically large (e.g., large bags or drums), taking up space during transportation and storage, and the proportion of active ingredients is relatively low. C) Dust Pollution Risk: Dust may be generated during processing, handling, or use, potentially impacting the respiratory health of operators and causing environmental pollution.

[0010] Reactive extrusion technology has emerged as a novel polymer material molding technology in recent years. It integrates the polymerization and processing processes, simultaneously carrying out chemical reactions and continuous production within the processing machinery. Reactive extrusion uses the extrusion equipment as a reaction vessel, achieving mixing, conveying, plasticizing, reacting, and extrusion of raw materials from the die during screw rotation. It offers advantages such as continuous large-scale production, low investment and cost, minimal or no use of solvents harmful to humans and the environment, a wide range of choices for products and raw materials, simplified polymer volatile removal, granulation, and molding processes, high reaction efficiency, and uniform product performance, demonstrating promising development prospects.

[0011] Currently, reactive extrusion, both domestically and internationally, mainly relies on twin-screw reactive extruders. The main problems include: ① The equipment is complex and requires a high initial investment.

[0012] ② Requires specialized engineering knowledge for scale-up design.

[0013] ③ Maintenance costs are relatively high.

[0014] The screw extruder kneader is a high-efficiency device that integrates mixing, kneading and continuous extrusion functions, and its price is lower than that of the twin-screw extruder. Summary of the Invention

[0015] This invention addresses the solubility, transportation, and storage problems of current solid water-soluble fertilizers by providing a method for using reactive extrusion granular solid fertilizers that rapidly transforms into slow-release clear liquid and suspension liquid fertilizers. These granular solid fertilizers not only possess advantages such as high dissolution rate and high particle strength, but also can be fully dissolved or dispersed in water to become slow-release clear liquid or suspension liquid fertilizers, enabling application through foliar spraying, seed soaking, root dipping, injection, drenching, watering, sprinkler irrigation, or drip irrigation. Furthermore, the processing technology is simple and cost-effective.

[0016] This invention is achieved through the following technical solution: a method for using reactive extrusion granular solid fertilizer that quickly becomes a slow-release clear liquid type and a suspension type liquid fertilizer. When the granular solid fertilizer is mixed with water at a ratio of 1kg:200-300L, it is stirred for 2-12 minutes until the granular solid fertilizer dissolves in the water, becoming a slow-release clear liquid type liquid fertilizer; when the granular solid fertilizer is mixed with water at a ratio of 1kg:1-5L, it is stirred for 10-20 minutes, and the granular solid fertilizer becomes a slow-release suspension type liquid fertilizer. The reactive extrusion production method for granular solid fertilizer includes the following steps: (1) Add formaldehyde to the reactor, then add a certain amount of urea and a certain amount of water, and react at 30-90°C for 0.5-4h to obtain hydroxymethylurea solution; (2) Turn on the kneading blades of the screw extruder kneader, add the hydroxymethyl urea solution obtained in step (1), essential plant nutrients and stabilizer to it, and knead for a certain time at a certain kneading temperature; during this process, hydroxymethyl urea undergoes a condensation reaction to become urea-formaldehyde; a viscous material is obtained; the essential plant nutrients account for more than 50% of the total mass of the fertilizer; the stabilizer accounts for 1-10% of the total mass of the fertilizer; (3) Turn on the discharge screw of the screw extrusion kneader so that the viscous material obtained in step (2) is continuously extruded into strips through the die of the screw extrusion kneader and simultaneously guided to slide into the top of the cooling conveyor belt; when cooled to 30-60°C by the cooling conveyor belt, it is transported to the granulator; after being granulated by the granulator, it becomes wet granules. (4) The wet granules obtained in step (3) are solidified at a certain temperature and dried for a certain time, and then cooled to room temperature to obtain the granular solid fertilizer that quickly becomes a slow-release clear liquid type and suspension type liquid fertilizer.

[0017] As a further improvement to the technical solution of the present invention, in step (1), the formaldehyde is at least one of solid formaldehyde, liquid formaldehyde and gaseous formaldehyde, and urea is added according to the molar ratio of formaldehyde to urea of ​​1:1-10, and the amount of water added is 0-60% of the total mass of formaldehyde and urea.

[0018] As a further improvement to the technical solution of the present invention, in step (2), the essential nutrients for plants include macronutrients and micronutrients; the macronutrients are selected from at least one of nitrogen, phosphorus and potassium; the micronutrients are selected from at least one of iron, manganese, zinc, copper, boron, molybdenum, silicon and sulfur.

[0019] As a further improvement to the technical solution of the present invention, in step (2), the stabilizer is selected from at least one of polymeric stabilizers and inorganic stabilizers; the polymeric stabilizer is selected from at least one of natural polymers and their derivatives, synthetic polymers and polymers, thixotropic polymeric materials and hydrophilic colloids; the natural polymers and their derivatives are selected from at least one of starch and its derivatives, gum arabic, gum resin, carboxymethyl cellulose and hydroxypropyl methyl cellulose; the synthetic polymers and polymers are selected from at least one of polyamide preparations, polyvinyl alcohol, polyacrylic acid and its salts, polymethyl methacrylate, maleic anhydride-styrene copolymers; the thixotropic polymeric materials are selected from at least one of aluminum monostearate, xanthan gum, sodium alginate and gellan gum; the hydrophilic colloid is selected from at least one of gelatin, carrageenan, guar gum and locust bean gum; and the inorganic stabilizer is selected from at least one of inorganic clays.

[0020] As a further improvement to the technical solution of the present invention, in step (2), the screw diameter of the screw extrusion kneader is 10-30 mm, the length-to-diameter ratio is 20-40:1, the rotation speed is 100-200 r / min, the torque is 300-5000 N·m, the heating power is 10-50 kW, the discharge method is die head extrusion, and the die diameter is 2-4 mm.

[0021] As a further improvement to the technical solution of the present invention, in step (3), the kneading temperature is 50-200°C and the kneading time is 5-30 min.

[0022] As a further improvement to the technical solution of the present invention, in step (4), the curing and drying temperature is 50-80°C and the time is 1-12h.

[0023] The method for rapidly converting reaction-extruded granular solid fertilizer into slow-release clear liquid and suspension liquid fertilizer provided by this invention has the following advantages compared with the prior art: (1) The present invention utilizes a kneader to achieve reactive extrusion, thereby significantly reducing the cost of reactive extrusion equipment.

[0024] (2) The present invention utilizes the process parameters control during the kneading process to cause hydroxymethyl urea to undergo a condensation reaction to become urea-formaldehyde. At the same time, the generated urea-formaldehyde is uniformly dispersed in the system by the action of the kneader blades. With its own adhesiveness, it effectively improves the mechanical strength of the prepared granular solid fertilizer, thereby giving the granular solid fertilizer good physical stability during storage, transportation and use.

[0025] (3) The granular solid fertilizer of the present invention, which rapidly transforms into slow-release clear liquid and suspension liquid fertilizers, has the advantages of high stability, convenient carrying and storage, relatively low cost, and wide applicability of powdered liquid fertilizers. At the same time, it solves the disadvantages of slow dissolution, easy generation of residues, need for special equipment, easy absorption of moisture and clumping, and risk of dust pollution. Through a unique solid structure and morphological design, it achieves rapid disintegration and efficient dissolution, significantly improving the fertilizer's speed of action and ease of application.

[0026] (4) The granular solid fertilizer prepared by the present invention, which can quickly become slow-release clear liquid and suspension liquid fertilizer, contains a large amount, medium amount and micro amount of nutrients required for plant growth and development. It can meet the nutrient requirements of crops without additional compounding, and the types and ratios of nutrients can be flexibly adjusted according to different plants and their growth stages.

[0027] (5) The preparation process of the present invention is simple and efficient, and the reaction and molding process is continuous and controllable. It can significantly reduce production energy consumption and operating costs, and has good adaptability to large-scale production, which is conducive to industrial promotion and application. Attached Figure Description

[0028] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0029] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0030] Figure 1 Digital photograph of the granular solid fertilizer prepared for Example 1, which rapidly becomes a slow-release clear liquid fertilizer and a suspension liquid fertilizer.

[0031] Figure 2 This is a slow-release clear liquid fertilizer formulated using the granular solid fertilizer prepared in Example 1 that rapidly becomes a slow-release clear liquid type and a suspension type liquid fertilizer.

[0032] Figure 3 This is a slow-release suspension liquid fertilizer formulated using the granular solid fertilizer prepared in Example 1, which rapidly becomes a slow-release clear liquid and suspension liquid fertilizer.

[0033] Figure 4 Slow-release suspension liquid fertilizer was formulated to prepare the granular solid fertilizer of Comparative Example 1.

[0034] Figure 5 This is a solid fertilizer prepared for Comparative Example 4. Detailed Implementation

[0035] To better understand the above-mentioned objectives, features, and advantages of the present invention, the solutions of the present invention will be further described below. It should be noted that, unless otherwise specified, the embodiments of the present invention and the features thereof can be combined with each other.

[0036] Many specific details are set forth in the following description in order to provide a full understanding of the invention, but the invention may also be practiced in other ways different from those described herein; obviously, the embodiments in the specification are only some embodiments of the invention, and not all embodiments.

[0037] The specific embodiments of the present invention will be described in detail below.

[0038] Example 1

[0039] A method for using reactive extrusion granular solid fertilizer that quickly transforms into slow-release clear liquid and suspension liquid fertilizer includes the following steps: (1) Add 4032g of liquid formaldehyde with a mass fraction of 37% and 5968g of urea (molar ratio of formaldehyde to urea is 1:2.0) to the reactor and react at 50°C for 2h to obtain hydroxymethylurea solution; (2) Start the kneading blades of the screw extrusion kneader (screw diameter 15mm, length-to-diameter ratio 25:1, rotation speed 120r / min, torque 500 N·m, heating power 20kW, discharge method is die head extrusion, die diameter 3mm) and add the hydroxymethyl urea solution obtained in step (1), substances containing essential plant nutrients (30000g KCl, 33000g NH4H2PO4 and 22000g (NH4)2SO4; the essential plant nutrients contained therein account for 54.02% of the total fertilizer mass) and 5000g of high molecular weight stabilizer gelatin (accounting for 5% of the total fertilizer mass), knead at 130°C for 10min; during this process, hydroxymethyl urea undergoes a condensation reaction to become urea-formaldehyde; a viscous material is obtained; (3) Turn on the discharge screw of the screw extrusion kneader so that the viscous material obtained in step (2) is continuously extruded into strips through the die of the screw extrusion kneader and simultaneously guided to slide into the top of the cooling conveyor belt; when cooled to 60°C by the cooling conveyor belt, it is transported to the granulator; after being granulated by the granulator, it becomes wet granules. (4) The wet granules obtained in step (3) are solidified at 60°C and dried to constant weight at the same time, which takes 8 hours. Then they are cooled to room temperature to obtain the granular solid fertilizer that quickly becomes a slow-release clear liquid type and suspension type liquid fertilizer.

[0040] Figure 1The photograph shows the granular solid fertilizer prepared in this embodiment. The granule strength is 5.68 MPa, and the content of nitrogen (11.62 wt%), phosphorus (P as P2O5) (20.65 wt%), potassium (K as K2O) (19.08 wt%), and sulfur (S) (5.48 wt%) is also described. When this granular solid fertilizer is mixed with water at a ratio of 1 kg:300 L, it dissolves in water after manual stirring for 3 minutes, becoming a slow-release clear liquid fertilizer with a nutrient concentration of 1.89 g / L. (See attached image.) Figure 2 When the granular fertilizer is mixed with water at a ratio of 1 kg: 2 L, manual stirring for 12 minutes will transform it into a slow-release suspension liquid fertilizer with a nutrient concentration of 284.20 g / L. (See [link / details]). Figure 3 .

[0041] Example 2

[0042] A method for using reactive extrusion granular solid fertilizer that quickly becomes a slow-release clear liquid and suspension liquid fertilizer is exactly the same as in Example 1, except that the molar ratio of formaldehyde and urea in step (1) is 1:1.8, that is, 4288 g of liquid formaldehyde with a mass fraction of 37% and 5712 g of urea are added.

[0043] The granular solid fertilizer prepared in this embodiment has a particle strength of 5.74 MPa, a nitrogen content of 11.52 wt%, a phosphorus content (P2O5) of 20.69 wt%, a potassium content (K2O) of 19.12 wt%, and a sulfur content of 5.49 wt%. When the granular solid fertilizer is mixed with water at a ratio of 1 kg:300 L, it can be dissolved in water by manual stirring for 4 minutes, becoming a slow-release clear liquid fertilizer with a nutrient concentration of 1.89 g / L. When the granular solid fertilizer is mixed with water at a ratio of 1 kg:2 L, it can be dissolved in water by manual stirring for 14 minutes, becoming a slow-release suspension liquid fertilizer with a nutrient concentration of 284.00 g / L.

[0044] Example 3

[0045] A method for using reactive extrusion granular solid fertilizer that quickly becomes a slow-release clear liquid and suspension liquid fertilizer is exactly the same as in Example 1, except that the molar ratio of formaldehyde and urea in step (1) is 1:2.2, that is, 3805g of liquid formaldehyde with a mass fraction of 37% and 6195g of urea are added.

[0046] The granular solid fertilizer prepared in this embodiment has a particle strength of 5.15 MPa, a nitrogen content of 11.74 wt%, a phosphorus content (P2O5) of 20.68 wt%, a potassium content (K2O) of 19.11 wt%, and a sulfur content of 5.48 wt%. When the granular solid fertilizer is mixed with water at a ratio of 1 kg: 300 L, it can be dissolved in water by manual stirring for 3 minutes, becoming a slow-release clear liquid fertilizer with a nutrient concentration of 1.90 g / L. When the granular solid fertilizer is mixed with water at a ratio of 1 kg: 2 L, it can be dissolved in water by manual stirring for 12 minutes, becoming a slow-release suspension liquid fertilizer with a nutrient concentration of 285.05 g / L.

[0047] Example 4

[0048] A method for using reactive extrusion granular solid fertilizer that quickly becomes a slow-release clear liquid and suspension liquid fertilizer is exactly the same as in Example 1, except that in step (2), the substances containing essential plant nutrients are 29000g KNO3, 41000g NH4H2PO4 and 10000g NH4Cl, of which the essential plant nutrients account for 54.14% of the total mass of the fertilizer.

[0049] The granular solid fertilizer prepared in this embodiment has a particle strength of 5.26 MPa, a nitrogen content of 11.11 wt%, a phosphorus content (P2O5) of 27.05 wt%, and a potassium content (K2O) of 14.62 wt%. When the granular solid fertilizer is mixed with water at a ratio of 1 kg: 300 L, it can be dissolved in water by manual stirring for 4.5 min, becoming a slow-release clear liquid fertilizer with a nutrient concentration of 1.76 g / L. When the granular solid fertilizer is mixed with water at a ratio of 1 kg: 2 L, it can be dissolved in water by manual stirring for 14 min, becoming a slow-release suspension liquid fertilizer with a nutrient concentration of 263.90 g / L.

[0050] Example 5

[0051] A method for using reactive extrusion granular solid fertilizer that quickly becomes a slow-release clear liquid and suspension liquid fertilizer is exactly the same as in Example 1, except that in step (2), the stabilizer accounting for 5% of the total mass of the fertilizer is the inorganic stabilizer bentonite.

[0052] The granular solid fertilizer prepared in this embodiment has a particle strength of 8.32 MPa, a nitrogen content of 11.62 wt%, a phosphorus content (P2O5) of 20.65 wt%, a potassium content (K2O) of 19.08 wt%, and a sulfur content of 5.48 wt%. When the granular solid fertilizer is mixed with water at a ratio of 1 kg: 300 L, it can be dissolved in water by manual stirring for 9 minutes, becoming a slow-release clear liquid fertilizer with a nutrient concentration of 1.89 g / L. When the granular solid fertilizer is mixed with water at a ratio of 1 kg: 2 L, it can be dissolved in water by manual stirring for 16 minutes, becoming a slow-release suspension liquid fertilizer with a nutrient concentration of 284.20 g / L.

[0053] Example 6

[0054] A method for using reactive extrusion granular solid fertilizer that quickly becomes a slow-release clear liquid and suspension liquid fertilizer is exactly the same as in Example 1, except that in step (2), the polymer stabilizer accounting for 5% of the total mass of the fertilizer is xanthan gum.

[0055] The granular solid fertilizer prepared in this embodiment has a particle strength of 8.15 MPa, a nitrogen content of 11.62 wt%, a phosphorus content (P2O5) of 20.65 wt%, a potassium content (K2O) of 19.08 wt%, and a sulfur content of 5.48 wt%. When the granular solid fertilizer is mixed with water at a ratio of 1 kg: 300 L, it can be dissolved in water by manual stirring for 4 minutes, becoming a slow-release clear liquid fertilizer with a nutrient concentration of 1.89 g / L. When the granular solid fertilizer is mixed with water at a ratio of 1 kg: 1 L, it can be dissolved in water by manual stirring for 17 minutes, becoming a slow-release suspension liquid fertilizer with a nutrient concentration of 568.4 g / L.

[0056] Example 7

[0057] A method for using reactive extruded granular solid fertilizer that quickly becomes a slow-release clear liquid and suspension liquid fertilizer is exactly the same as in Example 1, except that in step (2), the screw diameter of the screw extruder kneader is 30mm, the length-to-diameter ratio is 25:1, the rotation speed is 180r / min, the torque is 300N·m, the heating power is 25kW, and the discharge method is die head extrusion with a die diameter of 3mm.

[0058] The granular solid fertilizer prepared in this embodiment has a particle strength of 7.32 MPa, a nitrogen content of 11.62 wt%, a phosphorus content (P2O5) of 20.65 wt%, a potassium content (K2O) of 19.08 wt%, and a sulfur content of 5.48 wt%. When the granular solid fertilizer is mixed with water at a ratio of 1 kg: 300 L, it can be dissolved in water by manual stirring for 7 minutes, becoming a slow-release clear liquid fertilizer with a nutrient concentration of 1.89 g / L. When the granular solid fertilizer is mixed with water at a ratio of 1 kg: 2 L, it can be dissolved in water by manual stirring for 14 minutes, becoming a slow-release suspension liquid fertilizer with a nutrient concentration of 284.20 g / L.

[0059] Comparative Example 1

[0060] It is exactly the same as Example 1; except that no polymer stabilizer is added in step (2).

[0061] The granular solid fertilizer prepared in this comparative example has a particle strength of 5.71 MPa, a nitrogen content of 12.25 wt%, a phosphorus content (P2O5) of 21.77 wt%, a potassium content (K2O) of 20.12 wt%, and a sulfur content of 5.77 wt%. When this granular solid fertilizer is mixed with water at a ratio of 1 kg: 2 L, manual stirring for 12 minutes can produce a suspension fertilizer with a nutrient concentration of 299.55 g / L. However, this liquid fertilizer has poor stability because the suspended solid particles easily settle. Figure 4 .

[0062] Comparative Example 2

[0063] It is exactly the same as Example 1; except that in step (2), the polymer stabilizer accounts for 0.8% of the total mass of fertilizer, that is, the amount of gelatin added is 766.13g.

[0064] The granular solid fertilizer prepared in this comparative example has a particle strength of 5.68 MPa, a nitrogen content of 12.15 wt%, a phosphorus content (P2O5) of 21.59 wt%, a potassium content (K2O) of 19.95 wt%, and a sulfur content of 5.73 wt%. When this granular solid fertilizer is mixed with water at a ratio of 1 kg: 2 L, manual stirring for 12 minutes can turn it into a suspension fertilizer with a nutrient concentration of 297.10 g / L. However, the stability of this liquid fertilizer is poor because the suspended solid particles are prone to settling.

[0065] Comparative Example 3

[0066] It is exactly the same as Example 1; except that in step (2), the polymer stabilizer accounts for 15% of the total mass of fertilizer, that is, the amount of gelatin added is 16764.71g.

[0067] The granular solid fertilizer prepared in this comparative example has a particle strength of 4.62 MPa, a nitrogen content of 10.37 wt%, a phosphorus content (P2O5) of 18.43 wt%, a potassium content (K2O) of 17.03 wt%, and a sulfur content of 4.89 wt%. When this granular solid fertilizer is mixed with water at a ratio of 1 kg: 2 L, manual stirring for 13 minutes can produce a suspension fertilizer with a nutrient concentration of 253.55 g / L. However, the stability of this liquid fertilizer is poor because the particle size of the solid particles in the dispersion is too large, causing them to easily settle.

[0068] Comparative Example 4

[0069] It is exactly the same as Example 1; except that in step (2), the length-to-diameter ratio of the screw extrusion kneader is 15.

[0070] This proportion cannot be made into granular solid fertilizer. See Figure 5 .

[0071] Comparative Example 5

[0072] It is exactly the same as Example 1; except that in step (2), the length-to-diameter ratio of the screw extrusion kneader is 45.

[0073] This ratio cannot be used to make granular solid fertilizer.

[0074] Comparative Example 6

[0075] It is exactly the same as Example 1; except that in step (2), the speed of the screw extruder kneader does not reach 100 r / min.

[0076] This ratio cannot be used to make granular solid fertilizer.

[0077] Comparative Example 7

[0078] It is exactly the same as Example 1; except that in step (2), the rotation speed of the screw extruder kneader cannot be lower than 200 r / min.

[0079] This ratio cannot be used to make granular solid fertilizer.

[0080] Comparative Example 8

[0081] It is exactly the same as Example 1; except that in step (4), the curing and drying temperature is 40°C.

[0082] The granular solid fertilizer prepared in this comparative example has a particle strength of 4.32 MPa.

[0083] Comparative Example 9

[0084] It is exactly the same as Example 1; except that in step (4), the curing and drying temperature is 80°C.

[0085] The granular solid fertilizer prepared in this comparative example has a particle strength of 4.89 MPa. The content of nitrogen (11.62 wt%), phosphorus (P2O5) (20.65 wt%), potassium (K2O) (19.08 wt%), and sulfur (S) (5.48 wt%) is also present. When this granular solid fertilizer is mixed with water at a ratio of 1 kg:300 L, it requires manual stirring for 10 minutes to dissolve, but the resulting liquid fertilizer is not a clear liquid due to significant sedimentation. However, when mixed with water at a ratio of 1 kg:2 L, manual stirring for 12 minutes produces a suspension liquid fertilizer with a nutrient concentration of 284.20 g / L, but this liquid fertilizer exhibits poor stability because the suspended solid particles easily settle.

[0086] A comparison of Examples 1-7 and Comparative Examples 1-9 shows that the composition and ratio of raw materials, the main parameters of the kneader, and the preparation process parameters determine whether granular solid fertilizer can be successfully produced and whether the prepared solid fertilizer can be quickly converted into slow-release clear liquid fertilizer and suspension liquid fertilizer. Specific analysis is as follows: Regarding the composition and proportion of raw materials: As can be seen from the comparison between Comparative Examples 1-3 and Example 1, the suspension liquid fertilizer prepared from solid fertilizer has poor stability when no polymer stabilizer is added or the proportion of polymer stabilizer to the total mass of fertilizer is not appropriate, that is, the suspended particles are easy to settle.

[0087] Regarding the main parameters of the kneader: A comparison of Comparative Examples 4-7 and Example 1 shows that when the main parameters of the kneader are unsuitable, granular fertilizer cannot be obtained at all. In Comparative Example 4, the screw extrusion kneader had too small an aspect ratio, resulting in insufficient shearing action, making it impossible for hydroxymethylurea to undergo a condensation reaction to become urea-formaldehyde, thus preventing the production of granular fertilizer. In Comparative Example 5, the screw aspect ratio was too large, resulting in excessive shearing action, causing the urea-formaldehyde produced by the condensation reaction to undergo thermal degradation, also preventing the production of granular fertilizer. In Comparative Example 6, the rotation speed was too low, resulting in insufficient shearing action, making it impossible for hydroxymethylurea to undergo a condensation reaction to become urea-formaldehyde, thus preventing the production of granular fertilizer. In Comparative Example 7, the rotation speed was too high, resulting in excessive shearing action, causing the urea-formaldehyde produced by the condensation reaction to undergo thermal degradation, thus preventing the production of granular fertilizer.

[0088] Regarding the preparation process parameters: A comparison of Comparative Examples 8-9 and Example 1 shows that a suitable temperature range for both curing and drying is necessary to ensure the prepared solid fertilizer has the appropriate degree of curing, thereby achieving the required particle strength and obtaining stable slow-release clear liquid and suspension liquid fertilizers. The particle strength of the solid fertilizer obtained in Comparative Example 8 is significantly lower than that in Example 1 because the temperature was too low, resulting in insufficient curing and thus low particle strength. The high curing and drying temperature in Comparative Example 9 led to over-curing, causing excessive cross-linking of the material's internal structure, which in turn caused a series of performance degradation problems, such as a significant increase in fertilizer brittleness and a decrease in the stability of the prepared liquid fertilizer. Therefore, only a suitable curing and drying temperature is conducive to the full cross-linking and curing of the resin, forming a strong and tough network, and ensuring the acquisition of stable slow-release clear liquid and suspension liquid fertilizers.

[0089] The above description is merely a specific embodiment of the present invention, enabling those skilled in the art to understand or implement the present invention. Although detailed descriptions have been provided with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments, and they should all be covered within the protection scope of the claims.

Claims

1. A method for using reactive extrusion granular solid fertilizer that rapidly transforms into slow-release clear liquid and suspension liquid fertilizers, characterized in that... When the granular solid fertilizer is mixed with water at a ratio of 1kg:200-300L, stir for 2-12 minutes until the granular solid fertilizer dissolves in the water to become a slow-release clear liquid fertilizer; when the granular solid fertilizer is mixed with water at a ratio of 1kg:1-5L, stir for 10-20 minutes to become a slow-release suspension liquid fertilizer. The reactive extrusion production method for granular solid fertilizer includes the following steps: (1) Add formaldehyde to the reactor, then add a certain amount of urea and a certain amount of water, and react at 30-90°C for 0.5-4h to obtain hydroxymethylurea solution; (2) Turn on the kneading blades of the screw extruder kneader, add the hydroxymethyl urea solution obtained in step (1), essential plant nutrients and stabilizer to it, and knead for a certain time at a certain kneading temperature; during this process, hydroxymethyl urea undergoes a condensation reaction to become urea-formaldehyde; a viscous material is obtained; the essential plant nutrients account for more than 50% of the total mass of the fertilizer; the stabilizer accounts for 1-10% of the total mass of the fertilizer; (3) Turn on the discharge screw of the screw extrusion kneader so that the viscous material obtained in step (2) is continuously extruded into strips through the die of the screw extrusion kneader and simultaneously guided to slide into the top of the cooling conveyor belt; when cooled to 30-60°C by the cooling conveyor belt, it is transported to the granulator; after being granulated by the granulator, it becomes wet granules. (4) The wet granules obtained in step (3) are solidified at a certain temperature and dried for a certain time, and then cooled to room temperature to obtain the granular solid fertilizer that quickly becomes a slow-release clear liquid type and suspension type liquid fertilizer.

2. The method for using reactive extrusion granular solid fertilizer as described in claim 1, which rapidly transforms into slow-release clear liquid and suspension liquid fertilizers, is characterized in that... In step (1), the formaldehyde is at least one of solid formaldehyde, liquid formaldehyde and gaseous formaldehyde. Urea is added according to a molar ratio of formaldehyde to urea of ​​1:1-10. The amount of water added is 0-60% of the total mass of formaldehyde and urea.

3. The method for using reactive extrusion granular solid fertilizer as described in claim 1, which rapidly transforms into slow-release clear liquid and suspension liquid fertilizers, is characterized in that... In step (2), the essential nutrients for plants include macronutrients and micronutrients; the macronutrients are selected from at least one of nitrogen, phosphorus and potassium; the micronutrients are selected from at least one of iron, manganese, zinc, copper, boron, molybdenum, silicon and sulfur.

4. The method for using reactive extrusion granular solid fertilizer as described in claim 1, which rapidly transforms into slow-release clear liquid and suspension liquid fertilizers, is characterized in that... In step (2), the stabilizer is selected from at least one of polymeric stabilizers and inorganic stabilizers; the polymeric stabilizer is selected from at least one of natural polymers and their derivatives, synthetic polymers and polymers, thixotropic polymeric materials, and hydrophilic colloids; the natural polymers and their derivatives are selected from at least one of starch and its derivatives, gum arabic, gum resin, carboxymethyl cellulose, and hydroxypropyl methyl cellulose; the synthetic polymers and polymers are selected from at least one of polyamide preparations, polyvinyl alcohol, polyacrylic acid and its salts, polymethyl methacrylate, and maleic anhydride-styrene copolymers; the thixotropic polymeric materials are selected from at least one of aluminum monostearate, xanthan gum, sodium alginate, and gellan gum; the hydrophilic colloids are selected from at least one of gelatin, carrageenan, guar gum, and locust bean gum; and the inorganic stabilizer is selected from at least one of inorganic clays.

5. The method for using reactive extrusion granular solid fertilizer as described in claim 1, which rapidly transforms into slow-release clear liquid and suspension liquid fertilizers, is characterized in that... In step (2), the screw diameter of the screw extrusion kneader is 10-30 mm, the length-to-diameter ratio is 20-40:1, the rotation speed is 100-200 r / min, the torque is 300-5000 N·m, the heating power is 10-50 kW, and the discharge method is extrusion through the die head orifice with a die orifice diameter of 2-4 mm.

6. The method for using reactive extrusion granular solid fertilizer as described in claim 1, which rapidly transforms into slow-release clear liquid and suspension liquid fertilizers, is characterized in that... In step (3), the kneading temperature is 50-200°C and the kneading time is 5-30 min.

7. The method for using reactive extrusion granular solid fertilizer as described in claim 1, which rapidly transforms into slow-release clear liquid and suspension liquid fertilizers, is characterized in that... In step (4), the curing and drying temperature is 50-80°C and the time is 1-12h.

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