Superfine powder of dihydrogen potassium phosphate fertilizer for aerial application and preparation method thereof

Abstract

The application discloses a kind of superfine powder potassium dihydrogen phosphate fertilizer of aerial application and a preparation method thereof.The fertilizer is compounded by high-purity potassium dihydrogen phosphate, composite suspending dispersing agent, anti-caking aid and atomization spreading aid, and the component ratio is limited to the powder mass percentage index.The preparation method adopts a low-temperature spray drying coupled with airflow superfine grinding, grading screening integrated process, and the process parameters are accurately controlled.The obtained fertilizer powder has high uniformity, cold water instantaneous dissolution, and the suspension duration is more than 6h, without caking and hole blocking phenomenon.The crop leaf adhesion and absorption utilization rate are significantly improved, and the fertilizer is suitable for various unmanned aerial vehicle aerial operation, with excellent practicality and technical effect.

Description

Technical Field

[0001] This invention belongs to the field of agricultural fertilizer technology, specifically relating to an ultrafine powder potassium dihydrogen phosphate fertilizer for aerial spraying and its preparation method. Background Technology

[0002] Drone-based plant protection is a core technology for large-scale, intelligent operations in modern agriculture. It boasts advantages such as high efficiency, low labor costs, good spray uniformity, and suitability for large-area farmland operations, and has been widely applied to foliar fertilization and pest and disease control for food and cash crops. Potassium dihydrogen phosphate (KH2PO4) is the most widely used high-concentration water-soluble fertilizer in agriculture, characterized by high nutrient purity, rapid absorption rate, and significant yield-enhancing effects, making it a core fertilizer variety for aerial foliar fertilization.

[0003] Currently available commercially available and patented aerial spraying grade potassium dihydrogen phosphate powders generally suffer from core technical problems: wide particle size distribution, poor particle uniformity, and insufficient compatibility with matching adjuvant systems, resulting in slow fertilizer dissolution rate in cold water and poor suspension stability of aerial spraying solutions. Specifically, conventional potassium dihydrogen phosphate powders generally have a D50 greater than 15μm and a D90 greater than 30μm, with a mixture of coarse and fine particles. They cannot dissolve quickly and completely in low-temperature cold water environments, and the prepared aerial spraying solutions show obvious stratification and sedimentation after standing for 1-2 hours. At the same time, the powder is prone to absorbing moisture and clumping. In aerial spraying operations using drones with high-speed atomization and low-pressure spraying, settled particles easily clog the drone's micro-nozzles, causing spray interruptions and uneven atomization. This not only significantly reduces the efficiency of aerial spraying operations but also leads to uneven fertilization in the field, with some areas having excess nutrients and others lacking them. Furthermore, the settled fertilizer cannot adhere evenly to the crop leaves, resulting in a phosphorus and potassium nutrient absorption and utilization rate of less than 40%. This severely restricts the effectiveness of aerial fertilization in improving quality and efficiency and fails to meet the needs of large-scale, standardized drone aerial spraying operations. Existing technologies have not specifically addressed the core issues of precise control of powder particle size and synergistic compatibility with adjuvant systems, and cannot simultaneously meet the specific requirements of rapid dissolution, high suspension, anti-clogging, and anti-caking for aerial spraying. Summary of the Invention

[0004] This invention addresses the technical problems existing in the prior art by proposing an ultrafine powder potassium dihydrogen phosphate fertilizer for aerial spraying and its preparation method. It innovatively designs a precisely proportioned adjuvant compounding system and an integrated preparation process combining low-temperature spray drying with airflow ultrafine pulverization. By limiting the precise proportions of fertilizer components, powder particle size parameters, and physicochemical performance indicators, and matching them with a dedicated refined preparation process, it achieves ultrafine homogenization of the powder, instantaneous dissolution in cold water, long-term suspension of the pesticide solution, and anti-caking of the powder. This solves the technical problems of nozzle clogging, pesticide stratification and sedimentation, and low fertilizer utilization rate in drone aerial spraying operations, demonstrating significant practicality and technical effectiveness.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] An ultrafine potassium dihydrogen phosphate fertilizer for aerial application comprises, by mass percentage: 92.0%–96.0% high-purity potassium dihydrogen phosphate raw material, 2.0%–4.0% composite suspension dispersant, 1.0%–2.0% anti-caking agent, and 0.5%–1.0% atomization spreading agent; the ultrafine potassium dihydrogen phosphate fertilizer has a powder particle size D50 of 3–8 μm, a D90 ≤ 15 μm, and a moisture content ≤ 0.3%.

[0007] In a preferred embodiment of the present invention, the high-purity potassium dihydrogen phosphate raw material has a purity of ≥99.2%, a water-soluble phosphorus pentoxide content of ≥52.0%, a water-soluble potassium oxide content of ≥34.0%, and heavy metals lead, cadmium, and mercury content of ≤0.001%.

[0008] In a preferred embodiment of the present invention, the composite suspension dispersant is prepared by compounding modified sodium lignosulfonate and polyethylene glycol 4000 in a mass ratio of 2:1, wherein the modified sodium lignosulfonate is alkali-modified sodium lignosulfonate with a sulfonation degree of 1.8 to 2.2 mmol / g.

[0009] In a preferred embodiment of the present invention, the anti-caking agent is a composite of nano-silica and talc powder in a mass ratio of 3:1, wherein the nano-silica has a particle size of 20-50 nm and the talc powder has a mesh size of 3000 mesh.

[0010] In a preferred embodiment of the present invention, the atomizing and spreading aid is an organosilicon polyoxyethylene ether with a surface tension of 22-25 mN / m and an HLB value of 12-14.

[0011] In a preferred embodiment of the present invention, the bulk density of the ultrafine potassium dihydrogen phosphate fertilizer is 0.35–0.45 g / cm³. 3 Angle of repose ≤ 32°, powder flowability grade is 1.

[0012] In a preferred embodiment of the present invention, the aerial spraying solution prepared from the ultrafine potassium dihydrogen phosphate fertilizer has a static contact angle of 28° to 35° on the leaf surface and an adhesion rate of ≥92% on the crop leaf surface.

[0013] In a preferred embodiment of the present invention, the aerial spraying solution prepared by diluting the ultrafine potassium dihydrogen phosphate fertilizer by 500 to 1000 times shows no stratification or precipitation after standing at room temperature for 6 hours, and the atomized particle size of the solution is 80 to 120 μm.

[0014] A method for preparing ultrafine potassium dihydrogen phosphate fertilizer for aerial spraying includes the following steps: Step S1, raw material pretreatment: put high-purity potassium dihydrogen phosphate raw material into a constant temperature stirred tank, add deionized water to prepare a potassium dihydrogen phosphate aqueous solution with a mass concentration of 45% to 50%, stir at a constant temperature of 45 to 50℃ for 20 to 30 minutes, stirring speed of 300 to 400 r / min, filter to remove insoluble impurities, and obtain clear mother liquor. Step S2, compounding of additives: Add the composite suspending dispersant and atomizing spreading aid to the clarified mother liquor in sequence according to the ratio, stir at a constant temperature of 45℃ for 15 min, then add the anti-caking aid, and disperse by high-speed shearing for 10 min at a shearing speed of 800-1000 r / min to obtain a uniform mixture. Step S3, low-temperature spray drying: The mixture is fed into a centrifugal spray drying tower, the inlet air temperature is controlled at 110-120℃ and the outlet air temperature at 60-70℃, and the centrifugal atomization speed is 12000-14000 r / min, and the primary powder is obtained by drying. Step S4, airflow ultrafine grinding: The primary powder is fed into an airflow ultrafine grinder, the grinding pressure is 0.35-0.45MPa, and the classification speed is 3500-4000r / min, for ultrafine grinding and classification. Step S5, constant temperature conditioning and sieving: The pulverized powder is fed into a 300-mesh constant temperature vibrating screen, the sieving temperature is 25-30℃, the sieving time is 15-20min, and large particle impurities are removed. Step S6, Sealed Packaging: The qualified powder is vacuum-packed in a sealed, dust-free environment with humidity ≤30% and temperature 20~25℃ to obtain the finished ultrafine powder potassium dihydrogen phosphate fertilizer.

[0015] In a preferred embodiment of the present invention, in step S4, the particle size of the powder after airflow ultrafine grinding is strictly controlled to be D50 of 3-8μm and D90≤15μm; in step S3, the moisture content of the primary powder after spray drying is ≤2.0%; and in step S6, the moisture content of the finished product is precisely controlled to be ≤0.3%.

[0016] Compared with the prior art, the present invention has the following beneficial effects: 1. This invention addresses the core problems of existing aerial spraying methods for potassium dihydrogen phosphate, including uneven particle size, slow dissolution, poor suspension, and easy pore clogging and sedimentation. Through a precise additive compounding system and ultrafine powder control, it achieves rapid instantaneous dissolution in cold water, long-lasting suspension without stratification or sedimentation, and uniform powder particle size. This eliminates nozzle clogging and uneven spraying issues in drone aerial spraying operations, improving efficiency by over 40%.

[0017] 2. The powder exhibits excellent overall performance, making it suitable for large-scale, standardized aerial spraying operations. The powder has good flowability and moderate bulk density, making it compatible with automated dispensing and drone atomization systems. It ensures uniform atomization and strong droplet adhesion, increasing crop phosphorus and potassium nutrient absorption and utilization rates to over 85%, resulting in significant quality and yield improvements.

[0018] 3. Extremely stable storage, suitable for agricultural input distribution and long-term use. The product does not absorb moisture, clump, or lose active ingredients during long-term storage in a wide temperature range, maintaining stable shelf life and solving the storage problems of ultrafine powders, thus reducing agricultural input losses and costs.

[0019] 4. The process is simple and controllable, with high batch consistency and is environmentally friendly. The entire preparation process involves no high temperature or high pressure, no pollutant emissions, precise and controllable parameters, and can be mass-produced industrially. The product has no heavy metal residues, meets the needs of green agricultural development, and has a wide range of applications. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments or prior art, the drawings used in the description of the embodiments or prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 This is a schematic diagram of the components of an ultrafine powder potassium dihydrogen phosphate fertilizer applied by aerial spraying, provided as an embodiment of the present invention.

[0022] Figure 2 The flowchart illustrates a method for preparing ultrafine potassium dihydrogen phosphate fertilizer for aerial application, as provided in this embodiment of the invention.

[0023] Figure 3 This is a schematic diagram illustrating the stability test of a suspension of ultrafine potassium dihydrogen phosphate fertilizer applied by aerial spraying, as provided in an embodiment of the present invention.

[0024] Figure 4 This invention provides a schematic diagram of the static contact angle of the leaf surface of an aerial spraying solution of ultrafine potassium dihydrogen phosphate fertilizer, which is applied by aerial spraying.

[0025] Figure 5 This invention provides a storage effect diagram of ultrafine potassium dihydrogen phosphate fertilizer applied by aerial spraying. Detailed Implementation

[0026] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0027] like Figure 1As shown, this embodiment of the invention provides an ultrafine potassium dihydrogen phosphate fertilizer for aerial application, comprising the following components by mass percentage: 92.0%–96.0% high-purity potassium dihydrogen phosphate raw material, 2.0%–4.0% composite suspension dispersant, 1.0%–2.0% anti-caking agent, and 0.5%–1.0% atomization spreading agent; the ultrafine potassium dihydrogen phosphate fertilizer has a powder particle size D50 of 3–8 μm, D90 ≤ 15 μm, moisture content ≤ 0.3%, cold water dissolution time ≤ 10 s, and room temperature suspension stability time ≥ 6 h.

[0028] In terms of component ratio, 92.0%–96.0% high-purity potassium dihydrogen phosphate ensures the core nutrient content of the product and guarantees sufficient phosphorus and potassium nutrition supply; 2.0%–4.0% compound suspension dispersant can significantly improve the dispersibility and suspension stability of powder in water and prevent particle agglomeration and sedimentation; 1.0%–2.0% anti-caking adjuvant can prevent powder particles from contacting each other and prevent moisture absorption and agglomeration during storage and operation; 0.5%–1.0% atomization spreading adjuvant can reduce the surface tension of the liquid and improve the atomization effect of drones and the adhesion to crop leaves. In terms of performance parameters, the ultra-fine particle size is limited to D50 of 3-8μm and D90 of ≤15μm, which completely solves the problems of excessive particle size and uneven distribution of traditional powders; the moisture content is ≤0.3% to avoid powder agglomeration due to moisture absorption; the cold water dissolution time is ≤10s to achieve instantaneous dissolution without the need for warm water stirring, making it suitable for low-temperature field operations; the room temperature suspension time is ≥6h, which fully covers the duration of large-area drone spraying operations, eliminates the problem of pesticide stratification, sedimentation and pore blockage, and precisely solves the core defects of existing technologies.

[0029] In one embodiment, the purity, nutrient content, and heavy metal content of the core raw material, high-purity potassium dihydrogen phosphate, are precisely controlled. A purity of ≥99.2% for high-purity potassium dihydrogen phosphate eliminates impurities found in ordinary industrial-grade raw materials, preventing nozzle clogging and crop leaf contamination. Water-soluble phosphorus pentoxide ≥52.0% and water-soluble potassium oxide ≥34.0% ensure the product meets the nutrient standards for superior-grade aerial spraying fertilizer, guaranteeing sufficient fertilizer efficacy. The content of heavy metals lead, cadmium, and mercury is ≤0.001%, complying with green agricultural fertilization standards, preventing heavy metal residues from polluting the soil and crops, and improving product safety and compatibility.

[0030] In one embodiment, specifying the specific components and ratio of the composite suspending dispersant is a key technical feature for achieving high suspension stability of the pesticide solution. The composite suspending dispersant is composed of modified sodium lignosulfonate and polyethylene glycol 4000 in a 2:1 mass ratio. The modified sodium lignosulfonate is an alkali-modified sodium lignosulfonate with a sulfonation degree of 1.8–2.2 mmol / g. Modified sodium lignosulfonate possesses excellent anionic dispersion properties, adsorbing onto the surface of potassium dihydrogen phosphate powder particles to form an electrostatic repulsion layer, preventing particle agglomeration and sedimentation. Polyethylene glycol 4000 has good water solubility and steric hindrance effect, which can assist in dispersion and improve the stability of the pesticide solution system. The two are compounded in a 2:1 mass ratio, synergistically enhancing each other. Compared to a single dispersant, this can increase the suspension time of the pesticide solution by more than three times without affecting the powder dissolution rate, perfectly meeting the long-term stability requirements of aerial spraying pesticide solutions. The degree of sulfonation is limited to 1.8–2.2 mmol / g to ensure optimal dispersibility of modified sodium lignin sulfonate and avoid the problems of poor dispersion due to excessively low sulfonation and easy moisture absorption due to excessively high sulfonation.

[0031] In one embodiment, specifying the specific components, ratios, and specifications of the anti-caking agent is a core feature ensuring long-term powder storage stability and preventing agglomeration during operation. The anti-caking agent is a composite of nano-silica and talc in a 3:1 mass ratio. The nano-silica has a particle size of 20-50 nm, and the talc has a mesh size of 3000 mesh. The 20-50 nm nano-silica particles possess an ultra-large specific surface area, allowing them to uniformly adhere to the surface of potassium dihydrogen phosphate ultrafine particles, forming an isolation and protective layer. The 3000-mesh ultrafine talc possesses excellent lubricity and moisture resistance, filling the gaps between powder particles and preventing moisture adsorption. The 3:1 mass ratio of the two components synergistically achieves moisture-proof, isolation, and anti-agglomeration effects, ensuring that the powder does not agglomerate during long-term storage in a wide temperature range of 0-35°C, solving the problem of traditional ultrafine powders easily absorbing moisture, agglomerating, and clogging equipment.

[0032] In one embodiment, the specific type and performance parameters of the atomizing spreading aid are defined to suit the application conditions of drone-based aerial spraying. The atomizing spreading aid is an organosilicon polyoxyethylene ether with a surface tension of 22–25 mN / m and an HLB value of 12–14. Organosilicon polyoxyethylene ether is a highly efficient spreading aid suitable for foliar fertilizers. Its limited surface tension of 22–25 mN / m significantly reduces the surface tension of the spray solution, allowing the tiny droplets atomized by the drone to spread quickly and evenly on the crop leaves, preventing droplet roll-off and loss. An HLB value of 12–14 represents the optimal hydrophilic-lipophilic balance range, balancing the water solubility of the pesticide solution with leaf adhesion, improving the crop's absorption efficiency of phosphorus and potassium nutrients, while not affecting the powder's solubility and suspension stability.

[0033] In one embodiment, the bulk density and flowability parameters of the powder are defined to adapt to the conditions of drone-based aerial spraying and pesticide preparation. The bulk density of the ultrafine potassium dihydrogen phosphate fertilizer is 0.35–0.45 g / cm³, the angle of repose is ≤32°, and the powder flowability grade is Level 1. The bulk density of 0.35–0.45 g / cm³ is the optimal loose density for ultrafine powders, ensuring that the powder is loose and free from compaction and agglomeration, allowing for rapid dispersion into water during feeding without clumping or settling. The angle of repose of ≤32° corresponds to Level 1 powder flowability, ensuring uniform automatic powder feeding without bridging or clogging, making it suitable for automated aerial spraying equipment, improving the continuity and stability of aerial spraying operations, and overcoming the shortcomings of traditional powders with high bulk density, poor flowability, and easy clogging of feeding equipment.

[0034] In one embodiment, such as Figure 3 As shown, the aerial spraying solution prepared by diluting ultrafine potassium dihydrogen phosphate fertilizer 500-1000 times showed no stratification or sedimentation after standing at room temperature for 6 hours, with an atomized particle size of 80-120 μm. This specification limits the stability and atomization performance of the diluted spraying solution to suit actual field aerial spraying operations. A dilution of 500-1000 times is the conventional dilution ratio for agricultural aerial spraying. At this ratio, the solution showed no stratification or sedimentation after 6 hours, meeting the needs of continuous aerial spraying operations over large areas of farmland without frequent stirring, significantly improving operational efficiency. The atomized particle size of 80-120 μm is the optimal atomization particle size range for UAV aerial spraying, ensuring uniform atomization, strong droplet adhesion, and minimal drift, enabling precise and uniform foliar fertilization and improving nutrient utilization.

[0035] In one embodiment, such as Figure 4 As shown, the aerial spraying solution prepared from ultrafine potassium dihydrogen phosphate fertilizer has a static contact angle β of 28°–35° on the leaf surface, and an adhesion rate of ≥92% on crop leaves. This specific limitation on the product's foliar adhesion performance is a core technical feature that improves fertilizer utilization and reduces fertilizer waste. Through the synergistic effect of the atomizing and spreading adjuvants and ultrafine powders in the formula, the static contact angle on the leaf surface is precisely limited to 28°–35°. This angle range is the optimal adhesion angle for crop leaves, completely preventing fertilizer runoff and loss. The foliar adhesion rate is ≥92%, an improvement of more than 35% compared to ordinary products, significantly increasing the nutrient carrying capacity per unit area of ​​crop. This fundamentally solves the problems of poor adhesion and low utilization rate of traditional aerial spraying solutions, making it suitable for high-altitude drone spraying operations.

[0036] The above, such as Figure 5As shown, ultrafine potassium dihydrogen phosphate fertilizer exhibits no moisture absorption or clumping after 6 months of storage at 0–35℃, with an effective ingredient loss rate of ≤0.5%, solving the industry problem of poor storage stability of ultrafine powders. By limiting storage to a wide temperature range of 0–35℃ and allowing for 6 months of long-term storage without moisture absorption or clumping, and with an effective ingredient loss rate of ≤0.5%, the product maintains stable performance throughout its shelf life, and all aerial spraying compatibility indicators remain unchanged. Compared to traditional aerial spraying potassium dihydrogen phosphate, which clumps and becomes ineffective after 3 months of storage, this significantly improves storage stability, meeting the needs of bulk storage and long-term use of agricultural inputs.

[0037] The ultrafine powder potassium dihydrogen phosphate fertilizer exhibits a droplet drift rate of ≤6% and a droplet size uniformity coefficient of ≥0.85 during aerial spraying, with no fine droplet dispersion or large droplet fall. These parameters address the droplet drift defects inherent in drone-based aerial spraying, representing a core feature of this specialized technology. By limiting the droplet drift rate to ≤6% and the droplet size uniformity coefficient to ≥0.85, the uniformity of atomization is significantly improved compared to traditional potassium dihydrogen phosphate. This effectively prevents fertilizer waste and pesticide damage to surrounding crops caused by fine droplets drifting with the wind during high-altitude operations, while also avoiding localized fertilizer damage caused by concentrated large droplets falling. This ensures uniform fertilization in the field and is suitable for large-scale, cross-regional standardized aerial spraying operations.

[0038] After the ultrafine powder potassium dihydrogen phosphate fertilizer dries on crop leaves, it exhibits a rain-resistant leaching retention rate of ≥88%. Even after three washes with water at room temperature, the residual nutrients on the leaves still meet the crop's absorption needs. This rain-resistant performance addresses the industry-wide problem of nutrient loss after aerial spraying in the field. The ultrafine powder, combined with adjuvants, forms a uniform and breathable nutrient film on crop leaves, maintaining a rain-resistant leaching retention rate of ≥88%. Even after multiple rain washes, sufficient effective nutrients are retained, effectively solving the problems of easy leaching and short-term effectiveness of traditional potassium dihydrogen phosphate sprays, significantly extending the fertilizer's effectiveness period and making it suitable for aerial spraying operations in open field crops under variable weather conditions.

[0039] This ultrafine potassium dihydrogen phosphate fertilizer is suitable for aerial spraying operations in low-temperature environments ranging from 5 to 30°C. At 5°C in cold water, its dissolution time is ≤10 seconds, and its suspension stability time is ≥6 hours, with no crystallization or precipitation in low-temperature environments. This invention limits the product's adaptability to low-temperature aerial spraying, filling the technological gap caused by the failure of traditional products in low-temperature operations. Traditional potassium dihydrogen phosphate is prone to crystallization, dissolves slowly, and has poor suspension in cold water, failing to meet the needs of low-temperature aerial spraying in early spring and late autumn. This invention limits the dissolution time to ≤10 seconds and the suspension time to ≥6 hours at 5°C, with no crystallization or precipitation, making it suitable for aerial spraying operations across the entire temperature range of 5–30°C. This significantly broadens the product's applicable scenarios and demonstrates strong environmental adaptability and technological innovation.

[0040] like Figure 2 As shown in the figure, this embodiment of the invention also provides a method for preparing ultrafine potassium dihydrogen phosphate fertilizer for aerial application, comprising the following steps: Step S1, raw material pretreatment: put high-purity potassium dihydrogen phosphate raw material into a constant temperature stirred tank, add deionized water to prepare a potassium dihydrogen phosphate aqueous solution with a mass concentration of 45% to 50%, stir at a constant temperature of 45 to 50℃ for 20 to 30 minutes, stirring speed of 300 to 400 r / min, filter to remove insoluble impurities, and obtain clear mother liquor. Step S2, compounding of additives: Add the composite suspending dispersant and atomizing spreading aid to the clarified mother liquor in sequence according to the ratio, stir at a constant temperature of 45℃ for 15 min, then add the anti-caking aid, and disperse by high-speed shearing for 10 min at a shearing speed of 800-1000 r / min to obtain a uniform mixture. Step S3, low-temperature spray drying: The mixture is fed into a centrifugal spray drying tower, the inlet air temperature is controlled at 110-120℃ and the outlet air temperature at 60-70℃, and the centrifugal atomization speed is 12000-14000 r / min, and the primary powder is obtained by drying. Step S4, airflow ultrafine grinding: The primary powder is fed into an airflow ultrafine grinder, the grinding pressure is 0.35-0.45MPa, and the classification speed is 3500-4000r / min, for ultrafine grinding and classification. Step S5, constant temperature conditioning and sieving: The pulverized powder is fed into a 300-mesh constant temperature vibrating screen, the sieving temperature is 25-30℃, the sieving time is 15-20min, and large particle impurities are removed. Step S6, Sealed Packaging: The qualified powder is vacuum-packed in a sealed, dust-free environment with humidity ≤30% and temperature 20~25℃ to obtain the finished ultrafine powder potassium dihydrogen phosphate fertilizer.

[0041] In step S4, the particle size of the powder after airflow ultrafine grinding is strictly controlled to be D50 of 3-8μm and D90≤15μm. After spray drying in step S3, the moisture content of the primary powder is ≤2.0%. In step S6, the moisture content of the finished product is precisely controlled to be ≤0.3%.

[0042] The above steps include: raw material pretreatment, which removes impurities through constant-temperature stirring and filtration, preventing pore blockage caused by large particles and ensuring the purity of the mother liquor; and additive compounding, which employs a step-by-step feeding process—first dissolving and dispersing the additives, then adding the anti-caking additives—combined with high-speed shearing to achieve uniform mixing of the additives and mother liquor at the molecular level, preventing additive agglomeration and failure. The low-temperature spray drying step uses medium-low temperature drying to avoid additive decomposition and powder denaturation caused by high temperatures, ensuring initial uniform drying of the powder. The airflow ultrafine grinding step achieves ultrafine powder refining and precise particle size classification. Constant-temperature conditioning and sieving remove trace amounts of large particles, ensuring consistent powder particle size; and airtight, dust-free vacuum packaging prevents moisture absorption of the finished product, ensuring storage stability. The entire process is specifically tailored to the performance requirements of aerial spraying fertilizers.

[0043] Example 1 (Optimal Example) 1. Raw material ratio (mass percentage): 94.0% high-purity potassium dihydrogen phosphate, 3.0% composite suspension dispersant, 1.5% anti-caking agent, and 0.5% atomization spreading agent; the purity of high-purity potassium dihydrogen phosphate is 99.5%, the composite suspension dispersant is modified sodium lignosulfonate and polyethylene glycol 4000 = 2:1, the anti-caking agent is nano silica and talc = 3:1, and the atomization spreading agent is organosilicon polyoxyethylene ether.

[0044] 2. Preparation method: Step S1, raw material pretreatment: Prepare a 48% potassium dihydrogen phosphate aqueous solution, stir at 48℃ for 25 min at a speed of 350 r / min, filter to remove impurities and obtain a clear mother liquor; Step S2, compounding of additives: add the composite suspending dispersant and the atomizing spreading agent in sequence, stir at 45°C for 15 min, add the anti-caking agent, and shear at 900 r / min for 10 min to obtain the mixture; Step S3, low-temperature spray drying: inlet air temperature 115℃, outlet air temperature 65℃, atomization speed 13000r / min, drying to obtain primary powder with a moisture content of 1.2%; Step S4, airflow ultrafine grinding: grinding pressure 0.40MPa, classifying speed 3800r / min, powder after grinding D50=5μm, D90=12μm; Step S5, constant temperature sieving: sieve at 28℃ for 18 minutes, then sieve through a 300-mesh screen to remove impurities; Step S6, airtight packaging: vacuum packaging in an environment of 22°C and 25% humidity, with a finished product moisture content of 0.25%.

[0045] 3. Product performance testing: Cold water dissolution time 2.5s, room temperature suspension time 9.5h, angle of repose 30°, bulk density 0.40g / cm³ 3 It does not clump after 6 months of storage, and the loss rate of effective ingredients is 0.3%. When sprayed by aerial application, the atomized particle size of the 800-fold diluted solution is 100μm, with no stratification, sedimentation, or pore blockage.

[0046] Example 2 1. Raw material ratio (mass percentage): 92.0% high-purity potassium dihydrogen phosphate, 4.0% composite suspension dispersant, 2.0% anti-caking agent, 1.0% atomization spreading agent; other components are the same as in Example 1.

[0047] 2. Preparation method: Step S1: Prepare a 45% potassium dihydrogen phosphate aqueous solution, stir at 45℃ for 30 min at a speed of 300 r / min, and filter to remove impurities; Step S2, the additive compounding and shear dispersion process is the same as in Example 1; Step S3: Spray drying with inlet air temperature of 110℃, outlet air temperature of 60℃, and atomization speed of 12000r / min; Step S4: pulverization pressure 0.35MPa, classification speed 3500r / min, powder D50=8μm, D90=14μm; Step S5: Screen at 25℃ for 20 minutes; Step S6: Sealed packaging, finished product moisture content 0.28%.

[0048] 3. Product performance testing: Cold water dissolution time 2.8s, suspension time 8.2h, angle of repose 31°, no clumping after 6 months of storage, and no clogging or stratification of the spray solution during aerial spraying.

[0049] Example 3 1. Raw material ratio (mass percentage): 96.0% high-purity potassium dihydrogen phosphate, 2.0% composite suspension dispersant, 1.0% anti-caking agent, 1.0% atomization spreading agent; other components are the same as in Example 1.

[0050] 2. Preparation method: Step S1: Prepare a 50% potassium dihydrogen phosphate aqueous solution, stir at 50℃ for 20 min at a speed of 400 r / min, and filter to remove impurities; Steps S2-S3, the process parameters are the same as in Example 1; Step S4: pulverizing pressure 0.45 MPa, classifying speed 4000 r / min, powder D50=3 μm, D90=10 μm; Step S5: Screen at 30℃ for 15 minutes; Step S6: Sealed packaging, finished product moisture content 0.22%.

[0051] 3. Product performance testing: Cold water dissolution time 2.0s, suspension time 8.6h, angle of repose 29°, excellent powder flowability, and best atomization effect in aerial spraying.

[0052] Comparative Example 1 (Commonly available commercially available potassium dihydrogen phosphate for aerial spraying) Commercially available potassium dihydrogen phosphate for aerial spraying was selected, and its performance was tested as follows: powder D50=18μm, D90=32μm, cold water dissolution time 12s, suspension time 1.5h, angle of repose 38°, slight clumping after 3 months of storage, sedimentation and pore blockage of the pesticide solution after 2 hours of aerial spraying, and nutrient absorption rate 38%.

[0053] Comparative Example 2 (System without Composite Additives) Using only high-purity potassium dihydrogen phosphate and no additives, ultrafine powder was prepared using the process of this invention. The performance test results showed that the powder particle size met the standard, but the suspension time was only 2.0 h, the cold water dissolution time was 8 s, the leaf surface adhesion was poor, and the nutrient absorption rate was 52%.

[0054] Performance Comparison Analysis: Through comparison of the examples and comparative examples, it can be seen that the present invention solves the core technical problems of uneven particle size, slow dissolution, poor suspension, and easy clogging and agglomeration of traditional products by using precise component ratio, exclusive auxiliary agent compounding system and refined preparation process. Its various flight spraying adaptability performances far exceed those of existing products, and it has outstanding technical advantages.

[0055] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely preferred examples and are not intended to limit the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A type of ultrafine potassium dihydrogen phosphate fertilizer for aerial application, characterized in that, By mass percentage, it comprises the following components: 92.0%–96.0% high-purity potassium dihydrogen phosphate raw material, 2.0%–4.0% composite suspension dispersant, 1.0%–2.0% anti-caking agent, and 0.5%–1.0% atomization spreading agent; the ultrafine potassium dihydrogen phosphate fertilizer has a powder particle size D50 of 3–8 μm, a D90 ≤ 15 μm, and a moisture content ≤ 0.3%.

2. The ultrafine potassium dihydrogen phosphate fertilizer applied by aerial spraying according to claim 1, characterized in that, The high-purity potassium dihydrogen phosphate raw material has a purity of ≥99.2%, a water-soluble phosphorus pentoxide content of ≥52.0%, a water-soluble potassium oxide content of ≥34.0%, and heavy metals lead, cadmium, and mercury content of ≤0.001%.

3. The ultrafine potassium dihydrogen phosphate fertilizer applied by aerial spraying according to claim 1, characterized in that, The composite suspension dispersant is prepared by compounding modified sodium lignosulfonate and polyethylene glycol 4000 at a mass ratio of 2:

1. The modified sodium lignosulfonate is an alkali-modified sodium lignosulfonate with a sulfonation degree of 1.8 to 2.2 mmol / g.

4. The ultrafine potassium dihydrogen phosphate fertilizer applied by aerial spraying according to claim 1, characterized in that, The anti-caking agent is a composite of nano-silica and talc in a mass ratio of 3:1, wherein the nano-silica has a particle size of 20-50 nm and the talc has a mesh size of 3000 mesh.

5. The ultrafine potassium dihydrogen phosphate fertilizer applied by aerial spraying according to claim 1, characterized in that, The atomizing and spreading aid is an organosilicon polyoxyethylene ether with a surface tension of 22-25 mN / m and an HLB value of 12-14.

6. The ultrafine potassium dihydrogen phosphate fertilizer applied by aerial spraying according to claim 1, characterized in that, The bulk density of the ultrafine potassium dihydrogen phosphate fertilizer is 0.35–0.45 g / cm³. 3 Angle of repose ≤ 32°, powder flowability grade is 1.

7. The ultrafine potassium dihydrogen phosphate fertilizer applied by aerial spraying according to claim 1, characterized in that, The aerial spraying solution prepared from the ultrafine potassium dihydrogen phosphate fertilizer has a static contact angle of 28° to 35° on the leaf surface and an adhesion rate of ≥92% on the crop leaf surface.

8. The ultrafine potassium dihydrogen phosphate fertilizer applied by aerial spraying according to claim 1, characterized in that, The aerial spraying solution prepared by diluting the ultrafine potassium dihydrogen phosphate fertilizer 500 to 1000 times showed no stratification or precipitation after standing at room temperature for 6 hours, and the atomized particle size of the solution was 80 to 120 μm.

9. A method for preparing ultrafine potassium dihydrogen phosphate fertilizer applied by aerial spraying as described in any one of claims 1-8, characterized in that, Includes the following steps: Step S1, raw material pretreatment: put high-purity potassium dihydrogen phosphate raw material into a constant temperature stirred tank, add deionized water to prepare a potassium dihydrogen phosphate aqueous solution with a mass concentration of 45% to 50%, stir at a constant temperature of 45 to 50℃ for 20 to 30 minutes, stirring speed of 300 to 400 r / min, filter to remove insoluble impurities, and obtain clear mother liquor. Step S2, compounding of additives: Add the composite suspending dispersant and atomizing spreading aid to the clarified mother liquor in sequence according to the ratio, stir at a constant temperature of 45℃ for 15 min, then add the anti-caking aid, and disperse by high-speed shearing for 10 min at a shearing speed of 800-1000 r / min to obtain a uniform mixture. Step S3, low-temperature spray drying: The mixture is fed into a centrifugal spray drying tower, the inlet air temperature is controlled at 110-120℃ and the outlet air temperature at 60-70℃, and the centrifugal atomization speed is 12000-14000 r / min, and the primary powder is obtained by drying. Step S4, airflow ultrafine grinding: The primary powder is fed into an airflow ultrafine grinder, the grinding pressure is 0.35-0.45MPa, and the classification speed is 3500-4000r / min, for ultrafine grinding and classification. Step S5, constant temperature conditioning and sieving: The pulverized powder is fed into a 300-mesh constant temperature vibrating screen, the sieving temperature is 25-30℃, the sieving time is 15-20min, and large particle impurities are removed. Step S6, Sealed Packaging: The qualified powder is vacuum-packed in a sealed, dust-free environment with humidity ≤30% and temperature 20~25℃ to obtain the finished ultrafine powder potassium dihydrogen phosphate fertilizer.

10. The method for preparing ultrafine potassium dihydrogen phosphate fertilizer for aerial application according to claim 9, characterized in that, In step S4, the particle size of the powder after airflow ultrafine grinding is strictly controlled to be D50 of 3-8μm and D90≤15μm. After spray drying in step S3, the moisture content of the primary powder is ≤2.0%. In step S6, the moisture content of the finished product is precisely controlled to be ≤0.3%.

Images