Drum granulation method for water-soluble compound fertilizer

Abstract

The invention discloses a drum granulation method for a water-soluble compound fertilizer. The drum granulation method comprises the following steps: (1) crushing raw materials of a basic fertilizer; (2) uniformly stirring the crushed raw materials and a water-soluble modified starch solution to obtain a uniform mixture; (3) putting the obtained uniform mixture into a rotary drum granulator, and granulating to obtain a fertilizer particle mixture; (4) feeding the fertilizer particle mixture into a drying cylinder for drying treatment to obtain a dried fertilizer particle mixture; (5) performing primary cooling and secondary cooling on the dried fertilizer particle mixture to obtain a cooled fertilizer particle mixture; and (6) carrying out primary screening and secondary screening on the cooled fertilizer particle mixture to prepare a qualified fertilizer particle finished product. According to the invention, the physical properties and nutrient utilization rate of the fertilizer are improved by accurately controlling the use amount of the drum granulation raw materials of the water-soluble compound fertilizer and optimizing process parameters; and through the synergistic effect of the raw materials, the product quality can be obviously improved.

Description

Technical Field

[0001] The invention belongs to the technical field of fertilizer production, and in particular relates to a drum granulation method for water-soluble compound fertilizer. Background Art

[0002] Drum granulation is one of the common methods for compound fertilizer production, and is suitable for large-scale production of high, medium and low concentration compound fertilizers. Its main working mode is wet granulation, which uses a certain amount of water or steam to make the basic fertilizer fully mixed in the drum after moisture adjustment (not direct chemical reaction), and under certain liquid phase conditions, with a certain binder, with the help of the rotating motion of the drum, the material particles are squeezed and agglomerated into balls, and gradually roll and round to form the required fertilizer particles. Then, drying, cooling, screening and other processes are carried out to obtain the finished fertilizer product.

[0003] During the drum granulation process of compound fertilizer, a certain amount of binder must be added. Common binders used for compound fertilizer granulation include mineral raw materials such as bentonite, kaolin, attapulgite powder, and sepiolite powder. This type of binder has low cost and high adhesion, and has the effect of significantly increasing the yield of compound fertilizer. However, they also have the disadvantage of being insoluble, and they contain calcium, magnesium, silicon and other components. In the high-temperature drying process, they can form insoluble substances such as calcium phosphate, magnesium phosphate, and calcium silicate with phosphate, resulting in high hardness of fertilizer particles and poor water solubility.

[0004] In addition, the use of mineral binders is not suitable for the production of compound fertilizers with high nitrogen (N content ≥ 20%) or high potassium (K2O ≥ 18%) content due to their low yield. If production is required, the amount of binder added must exceed 7%-12%, which will greatly occupy the space for formula nutrients, compress the space for raw material selection, and increase the cost of production formula. Summary of the invention

[0005] The invention provides a drum granulation method for water-soluble compound fertilizer, so as to solve the problems of the existing drum granulation process for compound fertilizer, such as poor water solubility of the product and high cost of producing high-nitrogen and high-potassium products.

[0006] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0007] A method for drum granulation of water-soluble compound fertilizer comprises the following steps:

[0008] (1) crushing the raw materials of basic fertilizer;

[0009] (2) stirring the crushed raw material and the water-soluble modified starch solution to obtain a uniform mixture;

[0010] (3) placing the uniform mixture into a rotary drum granulator for granulation to obtain a fertilizer granular mixture;

[0011] (4) sending the fertilizer granule mixture into a drying drum for drying to obtain a dried fertilizer granule mixture;

[0012] (5) performing primary cooling and secondary cooling on the dried fertilizer granule mixture to obtain a cooled fertilizer granule mixture;

[0013] (6) The cooled fertilizer granule mixture is subjected to primary screening and secondary screening to obtain qualified fertilizer granule finished products.

[0014] Furthermore, the raw materials of the basic fertilizer in step (1) include, in parts by weight: 52-93 parts of urea, 35-56 parts of ammonium chloride, 13-20 parts of potassium sulfate, 16-24 parts of monoammonium phosphate, 1-1.5 parts of sodium dodecylbenzene sulfonate, 2-3 parts of hydroxyethyl cellulose, 5-9 parts of sodium hydroxyethylidene diphosphonate, 0.3-0.5 parts of acetohydroxamic acid, 0.2-0.4 parts of 3,4-dimethylpyrazole phosphate, and 1.6-2.3 parts of a synergist.

[0015] Furthermore, the raw materials of the basic fertilizer, in parts by weight, include: 72 parts of urea, 46 parts of ammonium chloride, 17 parts of potassium sulfate, 20 parts of monoammonium phosphate, 1.2 parts of sodium dodecylbenzene sulfonate, 2.6 parts of hydroxyethyl cellulose, 7 parts of sodium hydroxyethylidene diphosphonate, 0.4 parts of acetohydroxamic acid, 0.3 parts of 3,4-dimethylpyrazole phosphate, and 2 parts of synergist.

[0016] Furthermore, the method for preparing the water-soluble modified starch solution described in step (2) comprises the following steps:

[0017] Step 1: dispersing and dissolving starch in water to prepare a starch emulsion with a mass percentage of 12.3% to 48.6%;

[0018] Step 2: Add 3.2%-10.8% of vinyl acetate, 6.1%-14.5% of vinyl alcohol, 3.4%-8.2% of acrylic acid, 0.2%-0.4% of 2-acrylamido-2-methylpropanesulfonic acid, 0.1%-0.3% of sodium persulfate, 0.3%-0.5% of potassium bisulfite and 0.6%-1.4% of methylene succinic acid, 0.5%-1.2% of borax, and 0.1%-0.5% of potassium hydroxide aqueous solution to the starch emulsion prepared in step 1, and react for 0.5-1.2 hours under nitrogen protection to obtain starch emulsion a;

[0019] Step 3, adding 0.008%-0.15% sodium acrylate, 0.002%-0.04% potassium hydroxide aqueous solution, 0.003%-0.26% sodium lauryl sulfate, 0.001%-0.03% p-hydroxycinnamic acid, 0.002%-0.046% p-hydroxybenzoic acid and 0.002%-0.028% aminoformic acid to the starch emulsion a prepared in step 2, and reacting for 1-1.5 hours under nitrogen protection to prepare starch emulsion b;

[0020] Step 4: Add 0.003%-0.1% hydrochloric acid based on the dry weight of starch to the starch milk b prepared in step 3 to adjust the pH value of the solution to 5.6-6.2;

[0021] Step 5, heating the starch milk b adjusted with pH value in step 4 to 65-94° C. and keeping the temperature for 2-4 hours under microwave power of 100-200 W in a sealed condition to obtain starch milk c;

[0022] Step 6: heating the starch emulsion c obtained in step 5 at a pressure of 0.07-0.09 MPa to remove physically bound water at a heating temperature of 80-92° C. to obtain a water-soluble modified starch;

[0023] Step 7: Disperse and dissolve the water-soluble modified starch obtained in step 6 in water to obtain a water-soluble modified starch solution.

[0024] Furthermore, the starch in step one is one or more of water-soluble corn starch, water-soluble sweet potato starch, water-soluble cassava starch, water-soluble wheat starch, water-soluble rice starch, and water-soluble potato starch.

[0025] Furthermore, the water-soluble modified starch described in step seven is 1%-3% of the mass of the base fertilizer.

[0026] Furthermore, the mass concentration of the water-soluble modified starch solution in step seven is 32.6%-40.2%.

[0027] Furthermore, in step (4), the furnace head temperature of the drying drum is 180°C, and the furnace tail temperature is 60°C.

[0028] Furthermore, in step (6), the primary screening and the secondary screening use two sizes of sieves respectively. The first size is 4.75 mm, which passes through particles larger than 4.75 and re-granulates them after being crushed; the second size is 1.00 mm, which directly re-granulates powders and small particles smaller than 1.00 mm.

[0029] Furthermore, the particle size of the qualified fertilizer granules in step (6) is 1.00-4.75 mm.

[0030] Compared with the prior art, the present invention has the following advantages:

[0031] (1) During the entire preparation process of the water-soluble modified starch of the present invention, the careful selection and proportioning of each raw material, the precise control of the process parameters and the synergistic effect between each step have jointly contributed to the significant improvement of the performance of the water-soluble modified starch and achieved unexpected technical effects. These optimization measures not only improve production efficiency, but also reduce production costs, laying a solid foundation for the widespread application of starch modified products.

[0032] (2) The preparation method of the synergist of the present invention achieves effective synergy between the raw materials by finely controlling the dosage and process parameters of each raw material, which not only improves the comprehensive performance of the synergist, but also achieves unexpected technical effects. This process fully demonstrates the wisdom and sophistication in the field of chemical fertilizers and provides a valuable reference for the preparation of fertilizer synergists.

[0033] (3) The present invention precisely controls the amount of raw materials used in the drum granulation of water-soluble compound fertilizers and optimizes the process parameters. The drum granulation method of the water-soluble compound fertilizer of the present invention not only improves the physical properties and nutrient utilization rate of the fertilizer, but also achieves unexpected technical effects through the synergistic effect between the raw materials, thereby providing strong support for the sustainable development of modern agriculture.

[0034] (4) The innovation of the present invention lies not only in its major innovation of the traditional compound fertilizer rotary drum granulation technology, but also in that it significantly improves the core indicator of product quality - fertilizer water solubility in an unprecedented way. By deeply analyzing the limitations of existing processes, the present invention cleverly combines advanced material science principles and fine chemical technology, accurately controls the raw material ratio and the physical and chemical changes in the granulation process, and improves the water dispersion performance of compound fertilizer. This breakthrough directly responds to the market's urgent demand for efficient and easily absorbed fertilizers, and effectively solves the problems of uneven nutrient release and low crop absorption efficiency caused by poor water solubility. In practical applications, the compound fertilizer prepared by the present invention can dissolve more quickly in irrigation water, reduce nutrient loss, significantly improve fertilizer efficiency, and promote the absorption of nutrients by crop roots, thereby achieving an increase in crop yield and an improvement in quality, injecting strong impetus into the sustainable development of modern agriculture.

[0035] (5) When discussing the challenges facing the current compound fertilizer drum granulation process, we have to face up to a key technical bottleneck: when trying to produce compound fertilizers with high nitrogen (N content ≥ 20%) or high potassium (K2O ≥ 18%) content, the mineral binders traditionally relied on (such as bentonite, kaolin, attapulgite powder, sepiolite powder, etc.) seem to be unable to cope with the situation. Although these binders promote the formation of particles to a certain extent, their inherent physical and chemical properties limit their application in high-concentration nutrient compound fertilizers. Specifically, in the production process of high-nitrogen and high-potassium compound fertilizers, due to the significant increase in nutrient concentration, the demand for binding force between particles also increases significantly, and mineral binders often have difficulty in providing sufficient bonding strength, resulting in low yields and unstable particle quality. What is more serious is that in order to achieve the desired particle forming effect, the amount of mineral binder added has to be greatly increased, and this ratio often needs to exceed 7%-12%. This not only means that a large amount of precious formula nutrient space is occupied by non-functional binders, but also greatly compresses the range of raw material selection, limiting the flexibility and innovation of formula design. At the same time, the high amount of binder used directly pushes up the production cost and reduces the market competitiveness of the product. In this context, the present invention creatively introduces water-soluble modified starch as a new type of binder in the granulation process. This innovative measure fundamentally solves the production problem of high-nitrogen and high-potassium compound fertilizers. Water-soluble modified starch has shown excellent performance in the drum granulation process of compound fertilizers due to its excellent bonding properties, good water solubility and environmental friendliness. It can more effectively promote the close bonding between particles, and maintain a stable particle morphology and excellent physical properties even under high-concentration nutrient conditions, thereby significantly improving the yield and product quality. More importantly, compared with mineral binders, the amount of water-soluble modified starch added is greatly reduced, which effectively releases the nutrient space in the formula, allowing production to more flexibly select raw materials, optimize formula design, and produce high-quality compound fertilizers that are more in line with market demand. At the same time, due to the reduction in the amount of binder used, the production cost is significantly reduced, which can bring considerable economic benefits. It can be seen that the application of the water-soluble modified starch binder of the present invention in the compound fertilizer rotary drum granulation process not only solves the technical difficulties in the production of high-nitrogen and high-potassium compound fertilizers, but also brings significant technological progress and economic benefits to the compound fertilizer industry by improving production efficiency, reducing production costs, optimizing formula design, etc. This innovative achievement will undoubtedly inject new vitality and impetus into the future development of the compound fertilizer industry. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 The present invention is a flow chart of the drum granulation method for water-soluble compound fertilizer. DETAILED DESCRIPTION

[0037] In order to facilitate a better understanding of the present invention, the following examples are used to illustrate the present invention. These examples belong to the protection scope of the present invention, but do not limit the protection scope of the present invention.

[0038] In an embodiment, a method for preparing a water-soluble modified starch comprises the following steps:

[0039] Step 1: dispersing and dissolving starch in water to prepare a starch emulsion with a mass percentage of 12.3% to 48.6%;

[0040] Step 2: Add 3.2%-10.8% of vinyl acetate, 6.1%-14.5% of vinyl alcohol, 3.4%-8.2% of acrylic acid, 0.2%-0.4% of 2-acrylamido-2-methylpropanesulfonic acid, 0.1%-0.3% of sodium persulfate, 0.3%-0.5% of potassium bisulfite and 0.6%-1.4% of methylene succinic acid, 0.5%-1.2% of borax, and 0.1%-0.5% of potassium hydroxide aqueous solution to the starch emulsion prepared in step 1, and react for 0.5-1.2 hours under nitrogen protection to obtain starch emulsion a;

[0041] Step 3, adding 0.008%-0.15% sodium acrylate, 0.002%-0.04% potassium hydroxide aqueous solution, 0.003%-0.26% sodium lauryl sulfate, 0.001%-0.03% p-hydroxycinnamic acid, 0.002%-0.046% p-hydroxybenzoic acid and 0.002%-0.028% aminoformic acid to the starch emulsion a prepared in step 2, and reacting for 1-1.5 hours under nitrogen protection to prepare starch emulsion b;

[0042] Step 4: Add 0.003%-0.1% hydrochloric acid based on the dry weight of starch to the starch milk b prepared in step 3 to adjust the pH value of the solution to 5.6-6.2;

[0043] Step 5, heating the starch milk b adjusted with pH value in step 4 to 65-94° C. and keeping the temperature for 2-4 hours under microwave power of 100-200 W in a sealed condition to obtain starch milk c;

[0044] Step 6: heating the starch emulsion c obtained in step 5 at a pressure of 0.07-0.09 MPa to remove physically bound water at a heating temperature of 80-92° C. to obtain a water-soluble modified starch;

[0045] Step 7: Disperse and dissolve the water-soluble modified starch obtained in step 6 in water to obtain a water-soluble modified starch solution.

[0046] The starch in step 1 is one or more of water-soluble corn starch, water-soluble sweet potato starch, water-soluble cassava starch, water-soluble wheat starch, water-soluble rice starch and water-soluble potato starch.

[0047] The water-soluble modified starch described in step seven is 1%-3% of the mass of the base fertilizer.

[0048] The mass concentration of the water-soluble modified starch solution in step seven is 32.6%-40.2%.

[0049] like Figure 1 As shown, a method for drum granulation of water-soluble compound fertilizer comprises the following steps:

[0050] (1) crushing the raw materials of basic fertilizer;

[0051] (2) stirring the crushed raw material and the water-soluble modified starch solution to obtain a uniform mixture;

[0052] (3) placing the uniform mixture into a rotary drum granulator for granulation to obtain a fertilizer granular mixture;

[0053] (4) sending the fertilizer granule mixture into a drying drum for drying to obtain a dried fertilizer granule mixture;

[0054] (5) performing primary cooling and secondary cooling on the dried fertilizer granule mixture to obtain a cooled fertilizer granule mixture;

[0055] (6) The cooled fertilizer granule mixture is subjected to primary screening and secondary screening to obtain qualified fertilizer granule finished products.

[0056] The raw materials of the basic fertilizer in step (1) include, by weight, 52-93 parts of urea, 35-56 parts of ammonium chloride, 13-20 parts of potassium sulfate, 16-24 parts of monoammonium phosphate, 1-1.5 parts of sodium dodecylbenzene sulfonate, 2-3 parts of hydroxyethyl cellulose, 5-9 parts of sodium hydroxyethylidene diphosphonate, 0.3-0.5 parts of acetohydroxamic acid, 0.2-0.4 parts of 3,4-dimethylpyrazole phosphate, and 1.6-2.3 parts of a synergist.

[0057] The preparation method of the synergist comprises the following steps:

[0058] 1) preparing a suspension of 62-70 parts of sodium magnesium silicate with water, and dispersing the suspension with 3-5 parts of potassium metaphosphate to obtain a dispersed suspension;

[0059] 2) adding 14-20 parts of citric acid to the dispersed suspension obtained in step 1), and then acidifying the suspension at a temperature of 30-40° C. and a rotation speed of 200-300 r / min for 20-40 min to obtain an acidified material;

[0060] 3) adding the acidified material obtained in step 2), 7-16 parts of malonylurea and 2-4 parts of potassium thiosulfate catalyst into a reactor, performing polymerization reaction for 1.2-1.8 hours at a pressure of 2.5-4.8 MPa, a temperature of 72-78° C. and a rotation speed of 300-400 r / min, and filtering the obtained material;

[0061] 4) Add 1.2-1.5 parts of N,N′-ethylenediamine disuccinic acid to the material obtained in step 3), and carry out coating treatment at a temperature of 35-42° C. and a rotation speed of 250-350 r / min for 6-10 min to obtain a synergist.

[0062] In step (4), the furnace head temperature of the drying drum is 180°C, and the furnace tail temperature is 60°C.

[0063] In step (6), the primary screening and the secondary screening use two sizes of screens respectively. The first size is 4.75 mm, which passes through particles larger than 4.75 and re-granulates them after being crushed. The second size is 1.00 mm, which directly re-granulates powders and small particles smaller than 1.00 mm.

[0064] The particle size of the qualified fertilizer granules in step (6) is 1.00-4.75 mm.

[0065] Technical principle of the present invention:

[0066] 1. Preparation technology principle of water-soluble modified starch:

[0067] When deeply discussing the preparation method of the water-soluble modified starch of the present invention, we not only need to elaborate on the specific operations of each step, but also need to deeply analyze the unique role of each raw material, the synergistic mechanism between them, and the necessity of accurately controlling the amount of raw materials and process parameters, which together contribute to the significant improvement of the performance of the final product and achieve unexpected technical effects.

[0068] (1) Step 1: Preparation of starch emulsion

[0069] First, the starch is dispersed and dissolved in water to prepare a starch emulsion with a mass percentage of 12.3%-48.6%. This step is the basis of the entire preparation process. The concentration of the starch emulsion directly affects the efficiency of the subsequent reaction and the uniformity of the product. A high concentration of the emulsion helps to increase the reaction rate, but too high a concentration may lead to uneven reaction; conversely, a low concentration is conducive to uniform mixing, but it will reduce production efficiency. Therefore, it is crucial to accurately control this concentration range.

[0070] (2) Step 2: Addition and reaction of functional monomers

[0071] A variety of functional monomers (vinyl acetate, vinyl alcohol, acrylic acid, etc.) and catalysts (sodium persulfate, potassium bisulfite, etc.) and regulators (borax, potassium hydroxide aqueous solution, etc.) are added to the starch emulsion. The selection and ratio of these raw materials are carefully designed to introduce specific functional groups through copolymerization, thereby improving the water solubility, stability and functionality of starch. For example, the addition of vinyl acetate and vinyl alcohol can enhance the flexibility and water resistance of starch; acrylic acid gives it good water solubility and film-forming properties; and regulators such as 2-acrylamido-2-methylpropanesulfonic acid help control the reaction rate and product structure. The raw materials react under nitrogen protection to avoid oxidation side reactions caused by oxygen, ensuring the purity and efficiency of the reaction. Their synergistic effect makes the performance of the final product far superior to that of single-component modified starch.

[0072] (3) Step 3: Further modification and stabilization

[0073] Stabilizers such as sodium acrylate and various surfactants are added to the starch milk a prepared in step 2. These additives not only enhance the stability of the starch milk, but also promote the uniform dispersion of the particles and prevent the agglomeration of the particles. In particular, the appropriate addition of potassium hydroxide aqueous solution further adjusts the pH value of the system, creating favorable conditions for subsequent crosslinking and modification reactions. In this step, the trace addition of each additive can produce a significant effect, reflecting the importance of accurately controlling the dosage.

[0074] (4) Step 4: pH adjustment

[0075] The pH value of starch emulsion b was precisely adjusted to 5.6-6.2 by adding hydrochloric acid. The selection of this range is based on a deep understanding of the kinetics of starch modification reactions. The appropriate pH environment can maximize the reactivity of specific functional groups while inhibiting undesirable side reactions, thereby optimizing the performance of the product.

[0076] (5) Step 5: Heat treatment and microwave assistance

[0077] The starch milk with adjusted pH value is kept warm at a specific temperature (65-94℃) and microwave power (100-200W). The high efficiency and selectivity of microwave heating accelerate the rearrangement and cross-linking of starch molecules while maintaining the uniformity of the product. In this step, precise control of temperature and microwave power is the key to obtaining the ideal product structure. Too high a temperature may cause starch degradation, while too low a temperature is not enough to promote the reaction; the choice of microwave power directly affects the heating efficiency and reaction uniformity.

[0078] (6) Step 6: Removal of physically bound water

[0079] Finally, the water-soluble modified starch is obtained by heating and dehydrating by controlling the pressure and temperature. In this process, precise pressure and temperature control ensures the effective removal of physically bound water while avoiding excessive pyrolysis or coking of starch. The dehydrated starch not only has significantly improved water solubility, but also has better processing performance and stability.

[0080] (7) Step 7: Preparation of water-soluble modified starch solution

[0081] The amount of water-soluble modified starch added (1%-3% of the base fertilizer mass) is also crucial, which is directly related to the strength and stability of the fertilizer particles. This precise ratio not only improves the production efficiency of the fertilizer, but also ensures the consistency of the physical properties and nutrient content of the final product.

[0082] 2. Preparation technology principle of synergist:

[0083] When discussing the preparation method of the synergist in depth, we must not only elaborate on the specific operations of each step, but also deeply analyze the unique role of each raw material, how they work together to improve the overall performance of the synergist, and why precise control of raw material dosage and process parameters is crucial to achieving this technological breakthrough.

[0084] (1) Specific effects and synergistic mechanisms of raw materials

[0085] 1) Sodium magnesium silicate (62-70 parts): As a matrix material, sodium magnesium silicate provides a solid framework for the entire synergist system with its good adsorption, dispersibility and stability. The preparation of its suspension ensures that the subsequent components can be evenly dispersed, reducing agglomeration and improving overall uniformity.

[0086] 2) Potassium metaphosphate (3-5 parts): As a dispersant, potassium metaphosphate effectively reduces the interaction between sodium magnesium silicate particles through its unique chemical structure, further enhancing the dispersibility of the suspension, making the reaction in the subsequent steps more complete and uniform. This improvement in dispersibility lays a solid foundation for the high performance of the synergist.

[0087] 3) Citric acid (14-20 parts): In the acidification stage, citric acid not only acts as an acidifier to adjust the pH value of the system and promote certain chemical reactions, but also helps remove impurities in the suspension through its chelating effect and improves the purity of the product. At the same time, the addition of citric acid may also promote the activation of the surface functional groups of sodium magnesium silicate, creating favorable conditions for subsequent reactions.

[0088] 4) Malonyl urea (7-16 parts) and potassium thiosulfate catalyst (2-4 parts): These two play a key role in the polymerization reaction. Malonyl urea, as one of the reactants, participates in the construction of the core structure of the synergist, giving it specific functionality. Potassium thiosulfate, as a catalyst, significantly reduces the activation energy of the polymerization reaction, accelerates the reaction process, and makes the polymerization more efficient and orderly. The synergistic effect of the two not only improves the reaction efficiency, but also optimizes the structure of the product, thereby enhancing the effectiveness of the synergist.

[0089] 5) N,N′-ethylenediamine disuccinic acid (1.2-1.5 parts): During the coating treatment stage, this substance, as a coating agent, can form a protective film on the surface of the synergist particles, improve the stability of the synergist, and prevent it from being affected by the external environment and becoming ineffective during storage and use. In addition, the coating layer may also improve the interaction between the synergist and the target substance, further improving its use effect.

[0090] (2) Control of raw material dosage and process parameters

[0091] Precisely controlling the dosage of each raw material is the key to ensuring the stability of the synergist's performance. Too much or too little raw material may destroy the balance of the system and affect the final performance of the product. For example, the dosage of potassium metaphosphate needs to be moderate. Too little will result in poor dispersion, while too much may introduce unnecessary impurities. Similarly, the dosage of citric acid must also be precisely controlled to ensure that the ideal acidification effect is achieved without excessive corrosion of the base material.

[0092] The selection of process parameters is also crucial. The optimization of parameters such as temperature, pressure, and rotation speed can directly affect the reaction rate, product structure, and even the performance of the final product. For example, the appropriate polymerization temperature and pressure can ensure the smooth progress of the reaction while avoiding the formation of by-products; while the appropriate rotation speed can ensure that the materials are fully mixed in the reactor and improve the uniformity of the reaction.

[0093] 3. Technical principle of drum granulation of water-soluble compound fertilizer:

[0094] When deeply discussing the rotary drum granulation method of the water-soluble compound fertilizer of the present invention, we should not only elaborate on its operating steps, but also deeply analyze the specific role of the raw materials in each step, the synergistic mechanism between the raw materials, the necessity and importance of controlling the amount of raw materials, and the significant technical effects brought about by the optimization of process parameters.

[0095] (1) Specific effects and synergistic mechanisms of raw materials

[0096] 1) Urea (52-93 parts): As the main nitrogen source, urea has a high nitrogen content and good water solubility, making it an ideal choice for rapid release of nitrogen fertilizer. It can not only be quickly absorbed and utilized by crops to promote growth, but also form a synergistic effect with other nutrients to improve the overall fertilizer efficiency.

[0097] 2) Ammonium chloride (35-56 parts): As another nitrogen source, it complements urea and provides a continuous and stable nitrogen supply.

[0098] 3) Potassium sulfate (13-20 parts): Provides potassium, which is a key element for enhancing plant resistance and improving crop quality. It works synergistically with nitrogen and phosphorus to enhance plant photosynthesis efficiency and promote nutrient transport and storage.

[0099] 4) Monoammonium phosphate (16-24 parts): rich in phosphorus, one of the essential nutrients for crop growth, plays an important role in root development and flower and fruit formation. Monoammonium phosphate and urea can balance the nitrogen and phosphorus ratio and promote the overall growth of crops.

[0100] 5) Sodium dodecylbenzene sulfonate (1-1.5 parts): As a surfactant, it can effectively reduce the surface tension of the solution, promote the uniform dispersion and penetration of the water-soluble modified starch solution, and improve the granulation effect.

[0101] 6) Hydroxyethyl cellulose (2-3 parts), sodium hydroxyethyl diphosphonate (5-9 parts): Hydroxyethyl cellulose (HEC), as a high molecular polymer, plays a key role in water-soluble fertilizers with its excellent film-forming properties, water retention and viscosity. During the fertilizer preparation process, HEC can form a uniform and dense protective film that wraps around the surface of the fertilizer particles, effectively slowing down the dissolution rate of nutrients in the fertilizer. This film has good air permeability, which ensures that the crop roots can gradually obtain nutrients while avoiding waste and soil pollution caused by the sudden release of nutrients. In addition, the water retention of HEC can also promote soil moisture retention, which is conducive to the stability of the crop growth environment.

[0102] Hydroxyethylidene diphosphonate sodium (HEDP-Na) plays another important role in fertilizers with its excellent chelating ability and stability. It can form stable chelates with various metal ions in fertilizers (such as calcium, magnesium, iron, etc.), thereby reducing the antagonistic effect of these ions on fertilizer nutrients and improving the effectiveness and bioavailability of nutrients. At the same time, HEDP-Na also has a certain antibacterial effect, which can inhibit the growth of harmful microorganisms in the soil, protect fertilizers from microbial decomposition, and further extend the effective period of fertilizers.

[0103] When hydroxyethyl cellulose and sodium hydroxyethyl diphosphonate are used in water-soluble compound fertilizers at the same time, a significant synergistic effect is produced between them. The protective film formed by HEC provides a stable reaction environment for the chelation of HEDP-Na, reduces nutrient loss during the chelation process, and also enhances the water resistance and stability of the protective film. HEDP-Na further regulates the release rate of nutrients in the fertilizer through its chelation, complementing the slow-release effect of HEC and jointly achieving the slow-release of fertilizers. This synergistic effect not only prolongs the effective period of the fertilizer, but also greatly improves the utilization rate of nutrients and reduces the loss and waste of nutrients, which is of great significance for increasing crop yields, improving soil quality and protecting the environment.

[0104] 7) Acetohydroxamic acid (0.3-0.5 parts), 3,4-dimethylpyrazole phosphate (0.2-0.4 parts): As trace element synergists, they can activate the enzyme system in the plant, promote the absorption and utilization of trace elements, and further enhance the overall effect of the fertilizer.

[0105] 8) The synergist exhibits excellent chelation and adsorption capabilities. It can efficiently collect and adsorb key nutrients in a variety of fertilizers, including but not limited to ammonia, ammonium nitrogen, nitrate ions, soluble phosphorus and potassium ions. These adsorbed nutrients then cling tightly to the roots of crops, creating a local microcirculation environment that is conducive to nutrient absorption. This mechanism not only significantly promotes the effective use of nutrients by crops, but also effectively prevents unnecessary loss of nutrients.

[0106] It is particularly worth mentioning that the synergist cleverly solves several common problems in traditional fertilization: it effectively curbs the volatility of nitrogen (N), prevents the fixation trend of phosphorus (P), and improves the problem of potassium (K) leakage. This series of positive effects work together to greatly improve the overall fertilizer efficiency of water-soluble compound fertilizers, laying a solid foundation for the healthy growth and high yield of crops.

[0107] (2) The necessity and importance of raw material dosage control and process parameter optimization

[0108] 1) Raw material dosage control: Accurately controlling the ratio of each raw material is the key to ensuring balanced nutrition and stable performance of fertilizers. Excess or insufficient amount may affect the fertilizer efficiency and crop growth. For example, the adjustment of the nitrogen, phosphorus and potassium ratio needs to be carried out according to crop needs and soil conditions to achieve the best fertilization effect.

[0109] 2) Process parameter optimization:

[0110] a. Accuracy of raw material crushing: Crushing the raw materials of basic fertilizer is the initial step of the preparation process. The key to this step is to ensure that the raw material particle size is uniform and fine, which directly affects the uniformity and efficiency of subsequent mixing and granulation. Accurate control of the raw material particle size helps better penetration and bonding of the water-soluble modified starch solution, thereby improving the overall solubility and nutrient release rate of the fertilizer. Therefore, strict control of the degree of raw material crushing is the cornerstone of preparing high-quality water-soluble compound fertilizers.

[0111] b. Accurate ratio of raw materials and water-soluble modified starch solution: In step (2), the crushed raw materials are stirred with a water-soluble modified starch solution of a specific concentration to obtain a uniform mixture. The mass concentration of the water-soluble modified starch solution (32.6%-40.2%) used as a binder needs to be precisely controlled. Too high or too low a concentration will affect the viscosity of the mixture and the granulation effect.

[0112] c. High efficiency of drum granulation: The uniform mixture is fed into the drum granulator, where fertilizer granules are formed through rotation and shear force. In this step, the design, speed and operating conditions of the drum have a significant impact on the shape, size and uniformity of the granules. Reasonable setting of these parameters can maximize the use of raw materials, reduce energy consumption, and ensure the qualified rate of granules.

[0113] d. Temperature control of drying treatment: The selection of the furnace head temperature (180°C) and furnace tail temperature (60°C) of the drying drum is based on comprehensive consideration of the internal moisture evaporation rate and surface hardening of the fertilizer particles. This temperature gradient design can not only quickly remove excess moisture and prevent mildew or agglomeration caused by residual moisture inside the particles, but also ensure that the surface of the particles is moderately hardened to improve the durability and resistance to breakage of the particles. This optimization strategy significantly improves drying efficiency and reduces energy consumption.

[0114] e. Careful management of the cooling process: Primary cooling and secondary cooling are not only to lower the temperature of the fertilizer particles for subsequent processing and packaging, but more importantly to reduce the internal stress of the particles through gradual cooling, avoid thermal cracking, and ensure the integrity and appearance quality of the particles.

[0115] f. Strict control of the screening process: The first-level screening (4.75mm mesh screen) and the second-level screening (1.00mm mesh screen) ensure the particle size range of the final product (1.00-4.75mm), which is carefully set according to the absorption capacity of crop roots and the requirements of fertilization machinery. Through screening, the oversized or undersized particles are processed separately and re-granulated, which not only ensures the uniform application of fertilizers, but also avoids the waste of resources. In addition, this fine screening also promotes the uniform distribution of fertilizers in the soil and improves the utilization rate of nutrients.

[0116] In summary, the raw material dosage control and process parameter optimization in each step of the drum granulation method of water-soluble compound fertilizers are based on a deep understanding of fertilizer performance, production efficiency and environmental impact. These control measures not only improve the quality and stability of fertilizers, but also significantly reduce production costs, achieve efficient resource utilization and environmentally friendly protection, and reflect the urgent need for efficient and environmentally friendly fertilizer preparation technology in modern agricultural production.

[0117] The following is explained with more specific examples.

[0118] Example 1

[0119] A method for preparing a water-soluble modified starch comprises the following steps:

[0120] Step 1, dispersing and dissolving starch in water to prepare a starch emulsion with a mass percentage of 13.9%;

[0121] Step 2: Add 3.4% of vinyl acetate, 6.7% of vinyl alcohol, 3.5% of acrylic acid, 0.2% of 2-acrylamido-2-methylpropanesulfonic acid, 0.1% of sodium persulfate, 0.3% of potassium bisulfite, 0.7% of methylene succinic acid, 0.5% of borax, and 0.2% of potassium hydroxide aqueous solution to the starch emulsion prepared in step 1, and react under nitrogen protection for 1 hour to obtain starch emulsion a;

[0122] Step 3: Add 0.009% sodium acrylate, 0.002% potassium hydroxide aqueous solution, 0.003% sodium lauryl sulfate, 0.002% p-hydroxycinnamic acid, 0.002% p-hydroxybenzoic acid and 0.003% aminoformic acid to the starch emulsion a prepared in step 2, and react under nitrogen protection for 1.2 hours to prepare starch emulsion b;

[0123] Step 4: Add 0.003% hydrochloric acid based on the dry weight of starch to the starch milk b prepared in step 3 to adjust the pH value of the solution to 6.1;

[0124] Step 5, heating the starch milk b adjusted with pH value in step 4 to 70° C. and keeping the temperature for 4 h under microwave power of 100 W and sealed conditions to obtain starch milk c;

[0125] Step 6: heating the starch emulsion c obtained in step 5 at a pressure of 0.07 MPa to remove physically bound water at a heating temperature of 82° C. to obtain a water-soluble modified starch;

[0126] Step 7: Disperse and dissolve the water-soluble modified starch obtained in step 6 in water to obtain a water-soluble modified starch solution.

[0127] Step 1: the starch is water-soluble tapioca starch.

[0128] The water-soluble modified starch described in step seven is 1.2% of the mass of the base fertilizer.

[0129] The mass concentration of the water-soluble modified starch solution in step seven is 33.2%.

[0130] like Figure 1 As shown, a method for drum granulation of water-soluble compound fertilizer comprises the following steps:

[0131] (1) crushing the raw materials of basic fertilizer;

[0132] (2) stirring the crushed raw material and the water-soluble modified starch solution to obtain a uniform mixture;

[0133] (3) placing the uniform mixture into a rotary drum granulator for granulation to obtain a fertilizer granular mixture;

[0134] (4) sending the fertilizer granule mixture into a drying drum for drying to obtain a dried fertilizer granule mixture;

[0135] (5) performing primary cooling and secondary cooling on the dried fertilizer granule mixture to obtain a cooled fertilizer granule mixture;

[0136] (6) The cooled fertilizer granule mixture is subjected to primary screening and secondary screening to obtain qualified fertilizer granule finished products.

[0137] The raw materials of the basic fertilizer described in step (1) include, by weight, 54 parts of urea, 36 parts of ammonium chloride, 13 parts of potassium sulfate, 17 parts of monoammonium phosphate, 1 part of sodium dodecylbenzene sulfonate, 2 parts of hydroxyethyl cellulose, 5 parts of sodium hydroxyethylidene diphosphonate, 0.3 parts of acetohydroxamic acid, 0.2 parts of 3,4-dimethylpyrazole phosphate, and 1.7 parts of a synergist.

[0138] The preparation method of the synergist comprises the following steps:

[0139] 1) In parts by weight, 62.2 parts of sodium magnesium silicate are prepared into a suspension with water, and then the suspension is dispersed with 3 parts of potassium metaphosphate to obtain a dispersed suspension;

[0140] 2) adding 14.6 parts of citric acid to the dispersed suspension obtained in step 1), and then acidifying the suspension at a temperature of 30° C. and a rotation speed of 200 r / min for 40 min to obtain an acidified material;

[0141] 3) adding the acidified material obtained in step 2), 8 parts of malonylurea and 2 parts of potassium thiosulfate catalyst into a reactor, performing polymerization reaction for 1.8 hours at a pressure of 2.6 MPa, a temperature of 72° C. and a rotation speed of 300 r / min, and filtering the obtained material;

[0142] 4) 1.2 parts of N,N′-ethylenediamine disuccinic acid were added to the material obtained in step 3), and the coating treatment was carried out at a temperature of 36° C. and a rotation speed of 250 r / min for 10 minutes to obtain a synergist.

[0143] In step (4), the furnace head temperature of the drying drum is 180°C, and the furnace tail temperature is 60°C.

[0144] In step (6), the primary screening and the secondary screening use two sizes of screens respectively. The first size is 4.75 mm, which passes through particles larger than 4.75 and re-granulates them after being crushed. The second size is 1.00 mm, which directly re-granulates powders and small particles smaller than 1.00 mm.

[0145] The particle size of the qualified fertilizer granules in step (6) is 1.00-4.75 mm.

[0146] Example 2

[0147] A method for preparing a water-soluble modified starch comprises the following steps:

[0148] Step 1, dispersing and dissolving starch in water to prepare a 15.8% by weight starch emulsion;

[0149] Step 2: Add 4.1% of vinyl acetate, 7.2% of vinyl alcohol, 3.9% of acrylic acid, 0.2% of 2-acrylamido-2-methylpropanesulfonic acid, 0.13% of sodium persulfate, 0.34% of potassium bisulfite, 0.7% of methylene succinic acid, 0.6% of borax, and 0.2% of potassium hydroxide aqueous solution to the starch emulsion prepared in step 1, and react under nitrogen protection for 0.7h to obtain starch emulsion a;

[0150] Step 3: Add 0.01% sodium acrylate, 0.006% potassium hydroxide aqueous solution, 0.008% sodium lauryl sulfate, 0.007% p-hydroxycinnamic acid, 0.01% p-hydroxybenzoic acid and 0.005% aminoformic acid to the starch emulsion a prepared in step 2, and react under nitrogen protection for 1 hour to prepare starch emulsion b;

[0151] Step 4: Add 0.012% hydrochloric acid based on the dry weight of starch to the starch milk b prepared in step 3 to adjust the pH value of the solution to 6.0;

[0152] Step 5, heating the starch milk b adjusted with pH value in step 4 to 65° C. and keeping the temperature for 2 h under microwave power of 200 W and sealed conditions to obtain starch milk c;

[0153] Step 6: heating the starch emulsion c obtained in step 5 at a pressure of 0.07 MPa to remove physically bound water at a heating temperature of 82° C. to obtain a water-soluble modified starch;

[0154] Step 7: Disperse and dissolve the water-soluble modified starch obtained in step 6 in water to obtain a water-soluble modified starch solution.

[0155] Step 1: the starch is water-soluble corn starch.

[0156] The water-soluble modified starch described in step seven is 1.5% of the mass of the base fertilizer.

[0157] The mass concentration of the water-soluble modified starch solution in step seven is 35.4%.

[0158] like Figure 1 As shown, a method for drum granulation of water-soluble compound fertilizer comprises the following steps:

[0159] (1) crushing the raw materials of basic fertilizer;

[0160] (2) stirring the crushed raw material and the water-soluble modified starch solution to obtain a uniform mixture;

[0161] (3) placing the uniform mixture into a rotary drum granulator for granulation to obtain a fertilizer granular mixture;

[0162] (4) sending the fertilizer granule mixture into a drying drum for drying to obtain a dried fertilizer granule mixture;

[0163] (5) performing primary cooling and secondary cooling on the dried fertilizer granule mixture to obtain a cooled fertilizer granule mixture;

[0164] (6) The cooled fertilizer granule mixture is subjected to primary screening and secondary screening to obtain qualified fertilizer granule finished products.

[0165] The raw materials of the basic fertilizer described in step (1) include, by weight, 60 parts of urea, 39 parts of ammonium chloride, 14 parts of potassium sulfate, 18 parts of monoammonium phosphate, 1.1 parts of sodium dodecylbenzene sulfonate, 2.2 parts of hydroxyethyl cellulose, 6 parts of sodium hydroxyethylidene diphosphonate, 0.4 parts of acetohydroxamic acid, 0.3 parts of 3,4-dimethylpyrazole phosphate, and 1.8 parts of a synergist.

[0166] The preparation method of the synergist comprises the following steps:

[0167] 1) In parts by weight, 63 parts of sodium magnesium silicate are prepared into a suspension with water, and then the suspension is dispersed with 3.2 parts of potassium metaphosphate to obtain a dispersed suspension;

[0168] 2) adding 15 parts of citric acid to the dispersed suspension obtained in step 1), and then acidifying the suspension at a temperature of 32° C. and a rotation speed of 200 r / min for 40 min to obtain an acidified material;

[0169] 3) adding the acidified material obtained in step 2), 8 parts of malonylurea and 2.4 parts of potassium thiosulfate catalyst into a reactor, carrying out polymerization reaction for 1.8 hours at a pressure of 3 MPa, a temperature of 74° C. and a rotation speed of 300 r / min, and filtering the obtained material;

[0170] 4) 1.3 parts of N,N′-ethylenediamine disuccinic acid were added to the material obtained in step 3), and a coating treatment was carried out at a temperature of 38° C. and a rotation speed of 300 r / min for 8 minutes to obtain a synergist.

[0171] In step (4), the furnace head temperature of the drying drum is 180°C, and the furnace tail temperature is 60°C.

[0172] In step (6), the primary screening and the secondary screening use two sizes of screens respectively. The first size is 4.75 mm, which passes through particles larger than 4.75 and re-granulates them after being crushed. The second size is 1.00 mm, which directly re-granulates powders and small particles smaller than 1.00 mm.

[0173] The particle size of the qualified fertilizer granules in step (6) is 1.00-4.75 mm.

[0174] Example 3

[0175] A method for preparing a water-soluble modified starch comprises the following steps:

[0176] Step 1: dispersing and dissolving starch in water to prepare a 30% by weight starch emulsion;

[0177] Step 2: Add 7% of vinyl acetate, 10.2% of vinyl alcohol, 6.1% of acrylic acid, 0.3% of 2-acrylamido-2-methylpropanesulfonic acid, 0.2% of sodium persulfate, 0.4% of potassium bisulfite, 1% of methylene succinic acid, 0.9% of borax, and 0.3% of potassium hydroxide aqueous solution to the starch emulsion prepared in step 1, and react under nitrogen protection for 1 hour to obtain starch emulsion a;

[0178] Step 3: Add 0.05% sodium acrylate, 0.02% potassium hydroxide aqueous solution, 0.12% sodium lauryl sulfate, 0.015% p-hydroxycinnamic acid, 0.02% p-hydroxybenzoic acid and 0.01% aminoformic acid to the starch emulsion a prepared in step 2, and react under nitrogen protection for 1.3 hours to prepare starch emulsion b;

[0179] Step 4: Add 0.06% hydrochloric acid based on the dry weight of starch to the starch milk b prepared in step 3 to adjust the pH value of the solution to 5.8;

[0180] Step 5, heating the starch milk b adjusted with pH value in step 4 to 80° C. and keeping the temperature for 2 h under microwave power of 200 W and sealed conditions to obtain starch milk c;

[0181] Step 6: heating the starch emulsion c obtained in step 5 at a pressure of 0.08 MPa to remove physically bound water at a heating temperature of 85° C. to obtain a water-soluble modified starch;

[0182] Step 7: Disperse and dissolve the water-soluble modified starch obtained in step 6 in water to obtain a water-soluble modified starch solution.

[0183] Step 1: The starch is composed of water-soluble corn starch, water-soluble cassava starch and water-soluble wheat starch in a mass ratio of 1:2:1.

[0184] The water-soluble modified starch described in step seven is 2.2% of the mass of the base fertilizer.

[0185] The mass concentration of the water-soluble modified starch solution in step seven is 37.2%.

[0186] like Figure 1 As shown, a method for drum granulation of water-soluble compound fertilizer comprises the following steps:

[0187] (1) crushing the raw materials of basic fertilizer;

[0188] (2) stirring the crushed raw material and the water-soluble modified starch solution to obtain a uniform mixture;

[0189] (3) placing the uniform mixture into a rotary drum granulator for granulation to obtain a fertilizer granular mixture;

[0190] (4) sending the fertilizer granule mixture into a drying drum for drying to obtain a dried fertilizer granule mixture;

[0191] (5) performing primary cooling and secondary cooling on the dried fertilizer granule mixture to obtain a cooled fertilizer granule mixture;

[0192] (6) The cooled fertilizer granule mixture is subjected to primary screening and secondary screening to obtain qualified fertilizer granule finished products.

[0193] The raw materials of the basic fertilizer described in step (1) include, by weight, 72 parts of urea, 46 parts of ammonium chloride, 17 parts of potassium sulfate, 20 parts of monoammonium phosphate, 1.2 parts of sodium dodecylbenzene sulfonate, 2.6 parts of hydroxyethyl cellulose, 7 parts of sodium hydroxyethylidene diphosphonate, 0.4 parts of acetohydroxamic acid, 0.3 parts of 3,4-dimethylpyrazole phosphate, and 2 parts of synergist.

[0194] The preparation method of the synergist comprises the following steps:

[0195] 1) In parts by weight, 65 parts of sodium magnesium silicate are prepared into a suspension with water, and then the suspension is dispersed with 4 parts of potassium metaphosphate to obtain a dispersed suspension;

[0196] 2) adding 18 parts of citric acid to the dispersed suspension obtained in step 1), and then acidifying the suspension at a temperature of 35° C. and a rotation speed of 250 r / min for 26 min to obtain an acidified material;

[0197] 3) adding the acidified material obtained in step 2), 12 parts of malonylurea and 3 parts of potassium thiosulfate catalyst into a reactor, carrying out polymerization reaction for 1.6 hours at a pressure of 3.6 MPa, a temperature of 76° C. and a rotation speed of 350 r / min, and filtering the obtained material;

[0198] 4) 1.4 parts of N,N′-ethylenediamine disuccinic acid were added to the material obtained in step 3), and a coating treatment was carried out at a temperature of 40° C. and a rotation speed of 300 r / min for 8 minutes to obtain a synergist.

[0199] In step (4), the furnace head temperature of the drying drum is 180°C, and the furnace tail temperature is 60°C.

[0200] In step (6), the primary screening and the secondary screening use two sizes of screens respectively. The first size is 4.75 mm, which passes through particles larger than 4.75 and re-granulates them after being crushed. The second size is 1.00 mm, which directly re-granulates powders and small particles smaller than 1.00 mm.

[0201] The particle size of the qualified fertilizer granules in step (6) is 1.00-4.75 mm.

[0202] Example 4

[0203] A method for preparing a water-soluble modified starch comprises the following steps:

[0204] Step 1, dispersing and dissolving starch in water to prepare a starch emulsion with a mass percentage of 47.9%;

[0205] Step 2: Add 10.1% of vinyl acetate, 14% of vinyl alcohol, 8% of acrylic acid, 0.4% of 2-acrylamido-2-methylpropanesulfonic acid, 0.3% of sodium persulfate, 0.5% of potassium bisulfite, 1.2% of methylene succinic acid, 1.1% of borax, and 0.4% of potassium hydroxide aqueous solution to the starch emulsion prepared in step 1, and react under nitrogen protection for 0.8h to obtain starch emulsion a;

[0206] Step 3: Add 0.12% sodium acrylate, 0.04% potassium hydroxide aqueous solution, 0.25% sodium lauryl sulfate, 0.03% p-hydroxycinnamic acid, 0.042% p-hydroxybenzoic acid and 0.023% aminoformic acid to the starch emulsion a prepared in step 2, and react under nitrogen protection for 1.4 hours to prepare starch emulsion b;

[0207] Step 4: Add 0.1% hydrochloric acid based on the dry weight of starch to the starch milk b prepared in step 3 to adjust the pH value of the solution to 5.6;

[0208] Step 5, raising the temperature of the starch milk b adjusted with pH value in step 4 to 92° C. and keeping the temperature for 2 h under a microwave power of 200 W and sealed conditions to obtain starch milk c;

[0209] Step 6: heating the starch emulsion c obtained in step 5 at a pressure of 0.09 MPa to remove physically bound water at a heating temperature of 90° C. to obtain a water-soluble modified starch;

[0210] Step 7: Disperse and dissolve the water-soluble modified starch obtained in step 6 in water to obtain a water-soluble modified starch solution.

[0211] Step one: the starch is rice starch.

[0212] The water-soluble modified starch described in step seven is 3% of the mass of the base fertilizer.

[0213] The mass concentration of the water-soluble modified starch solution in step seven is 39.6%.

[0214] like Figure 1 As shown, a method for drum granulation of water-soluble compound fertilizer comprises the following steps:

[0215] (1) crushing the raw materials of basic fertilizer;

[0216] (2) stirring the crushed raw material and the water-soluble modified starch solution to obtain a uniform mixture;

[0217] (3) placing the uniform mixture into a rotary drum granulator for granulation to obtain a fertilizer granular mixture;

[0218] (4) sending the fertilizer granule mixture into a drying drum for drying to obtain a dried fertilizer granule mixture;

[0219] (5) performing primary cooling and secondary cooling on the dried fertilizer granule mixture to obtain a cooled fertilizer granule mixture;

[0220] (6) The cooled fertilizer granule mixture is subjected to primary screening and secondary screening to obtain qualified fertilizer granule finished products.

[0221] The raw materials of the basic fertilizer described in step (1) include, by weight, 90 parts of urea, 54 parts of ammonium chloride, 18 parts of potassium sulfate, 22 parts of monoammonium phosphate, 1.3 parts of sodium dodecylbenzene sulfonate, 2.8 parts of hydroxyethyl cellulose, 8.7 parts of sodium hydroxyethylidene diphosphonate, 0.5 parts of acetohydroxamic acid, 0.4 parts of 3,4-dimethylpyrazole phosphate, and 2.2 parts of synergist.

[0222] The preparation method of the synergist comprises the following steps:

[0223] 1) In parts by weight, 68 parts of sodium magnesium silicate are prepared into a suspension with water, and then the suspension is dispersed with 5 parts of potassium metaphosphate to obtain a dispersed suspension;

[0224] 2) adding 18 parts of citric acid to the dispersed suspension obtained in step 1), and then acidifying the suspension at a temperature of 38° C. and a rotation speed of 300 r / min for 24 min to obtain an acidified material;

[0225] 3) adding the acidified material obtained in step 2), 15 parts of malonylurea and 3.8 parts of potassium thiosulfate catalyst into a reactor, performing polymerization reaction for 1.3 hours at a pressure of 4.5 MPa, a temperature of 76° C. and a rotation speed of 400 r / min, and filtering the obtained material;

[0226] 4) 1.4 parts of N,N′-ethylenediamine disuccinic acid were added to the material obtained in step 3), and a coating treatment was carried out at a temperature of 40° C. and a rotation speed of 300 r / min for 9 minutes to obtain a synergist.

[0227] In step (4), the furnace head temperature of the drying drum is 180°C, and the furnace tail temperature is 60°C.

[0228] In step (6), the primary screening and the secondary screening use two sizes of screens respectively. The first size is 4.75 mm, which passes through particles larger than 4.75 and re-granulates them after being crushed. The second size is 1.00 mm, which directly re-granulates powders and small particles smaller than 1.00 mm.

[0229] The particle size of the qualified fertilizer granules in step (6) is 1.00-4.75 mm.

[0230] Comparative Example 1

[0231] This comparative example is basically the same as Example 3, except that conventional mineral binder bentonite is used to replace the water-soluble modified starch of the present invention, and the amount used is the same, specifically as follows:

[0232] A method for drum granulation of water-soluble compound fertilizer comprises the following steps:

[0233] (1) crushing the raw materials of basic fertilizer;

[0234] (2) The crushed raw material, bentonite and water (the amount of water added is the same as in Example 3) are stirred uniformly to obtain a uniform mixture, wherein the bentonite accounts for 2.2% of the mass of the base fertilizer;

[0235] (3) placing the uniform mixture into a rotary drum granulator for granulation to obtain a fertilizer granular mixture;

[0236] (4) sending the fertilizer granule mixture into a drying drum for drying to obtain a dried fertilizer granule mixture;

[0237] (5) performing primary cooling and secondary cooling on the dried fertilizer granule mixture to obtain a cooled fertilizer granule mixture;

[0238] (6) The cooled fertilizer granule mixture is subjected to primary screening and secondary screening to obtain qualified fertilizer granule finished products.

[0239] The raw materials of the basic fertilizer described in step (1) include, by weight, 72 parts of urea, 46 parts of ammonium chloride, 17 parts of potassium sulfate, 20 parts of monoammonium phosphate, 1.2 parts of sodium dodecylbenzene sulfonate, 2.6 parts of hydroxyethyl cellulose, 7 parts of sodium hydroxyethylidene diphosphonate, 0.4 parts of acetohydroxamic acid, 0.3 parts of 3,4-dimethylpyrazole phosphate, and 2 parts of synergist.

[0240] The preparation method of the synergist comprises the following steps:

[0241] 1) In parts by weight, 65 parts of sodium magnesium silicate are prepared into a suspension with water, and then the suspension is dispersed with 4 parts of potassium metaphosphate to obtain a dispersed suspension;

[0242] 2) adding 18 parts of citric acid to the dispersed suspension obtained in step 1), and then acidifying the suspension at a temperature of 35° C. and a rotation speed of 250 r / min for 26 min to obtain an acidified material;

[0243] 3) adding the acidified material obtained in step 2), 12 parts of malonylurea and 3 parts of potassium thiosulfate catalyst into a reactor, carrying out polymerization reaction for 1.6 hours at a pressure of 3.6 MPa, a temperature of 76° C. and a rotation speed of 350 r / min, and filtering the obtained material;

[0244] 4) 1.4 parts of N,N′-ethylenediamine disuccinic acid were added to the material obtained in step 3), and a coating treatment was carried out at a temperature of 40° C. and a rotation speed of 300 r / min for 8 minutes to obtain a synergist.

[0245] In step (4), the furnace head temperature of the drying drum is 180°C, and the furnace tail temperature is 60°C.

[0246] In step (6), the primary screening and the secondary screening use two sizes of screens respectively. The first size is 4.75 mm, which passes through particles larger than 4.75 and re-granulates them after being crushed. The second size is 1.00 mm, which directly re-granulates powders and small particles smaller than 1.00 mm.

[0247] The particle size of the qualified fertilizer granules in step (6) is 1.00-4.75 mm.

[0248] 1. Soil microbial activity test

[0249] Four test plots with basically the same conditions were selected in Long'an County, Nanning City, each plot was 1 mu, and the compound fertilizers of Examples 1 to 4 of the present invention were applied to the 1st to 4th plots respectively. The amount of fertilizer applied to the four test plots was equal, and the same fertilization method was used. The soil microbial activity (soil respiration rate, microbial biomass carbon, soil enzyme activity) was measured 3 months after fertilization, and the results are shown in the following table.

[0250]

[0251] It can be seen from the above table that the compound fertilizer prepared by the present invention has high soil microbial activity and can meet the needs of promotion and application.

[0252] (II) Comparative test on the effect of improving crop yield and quality

[0253] In a certain Wogan orchard in Wuming District, Nanning City, three-year-old Wogan fruit trees with basically the same regional environment and similar growth were selected and divided into 5 plots on average, with 90 trees in each plot. The compound fertilizers of Examples 1-4 and Comparative Example 1 were used respectively. The fertilizer amounts of the 5 test plots were equal, and the same fertilization method was adopted. The average yield of Wogan and the average soluble solids content of each plot were counted.

[0254]

[0255] It can be seen from the above table that: (1) the average yield of Wogan obtained by using the compound fertilizer of the present invention reaches more than 35.68 kg / plant, and the average soluble solid content of Wogan reaches more than 14.60%, indicating that the application of the compound fertilizer of the present invention can obtain a higher yield of Wogan with excellent quality and improve economic benefits.

[0256] (2) The average yield of oranges obtained by using the compound fertilizer of Example 3 of the present invention is 4.72 kg / plant higher than the average yield of oranges obtained by using the compound fertilizer of Comparative Example 1, with an increase of 14.87%; the average soluble solids content of oranges obtained by using the compound fertilizer of Example 3 of the present invention is 0.92% higher than the average soluble solids content of oranges obtained by using the compound fertilizer of Comparative Example 1, indicating that the compound fertilizer of the present invention has significant advantages over the prior art in improving crop yield and quality.

[0257] The above content cannot be used to determine that the specific implementation of the present invention is limited to these descriptions. For ordinary technicians in the technical field to which the present invention belongs, they can make several simple deductions or substitutions without departing from the concept of the present invention, which should be regarded as belonging to the scope of patent protection of the present invention determined by the submitted claims.

Claims

1. A method for drum granulation of water-soluble compound fertilizer, characterized in that: The following steps are involved: (1) crushing the raw materials of basic fertilizer; (2) stirring the crushed raw material and the water-soluble modified starch solution to obtain a uniform mixture; (3) placing the uniform mixture into a rotary drum granulator for granulation to obtain a fertilizer granular mixture; (4) sending the fertilizer granule mixture into a drying drum for drying to obtain a dried fertilizer granule mixture; (5) performing primary cooling and secondary cooling on the dried fertilizer granule mixture to obtain a cooled fertilizer granule mixture; (6) The cooled fertilizer granule mixture is subjected to primary screening and secondary screening to obtain qualified fertilizer granule finished products.

2. The method for drum granulation of water-soluble compound fertilizer according to claim 1, characterized in that: The raw materials of the basic fertilizer in step (1) include, by weight, 52-93 parts of urea, 35-56 parts of ammonium chloride, 13-20 parts of potassium sulfate, 16-24 parts of monoammonium phosphate, 1-1.5 parts of sodium dodecylbenzene sulfonate, 2-3 parts of hydroxyethyl cellulose, 5-9 parts of sodium hydroxyethylidene diphosphonate, 0.3-0.5 parts of acetohydroxamic acid, 0.2-0.4 parts of 3,4-dimethylpyrazole phosphate, and 1.6-2.3 parts of a synergist.

3. The method for drum granulation of water-soluble compound fertilizer according to claim 2, characterized in that: The raw materials of the basic fertilizer include, in parts by weight, 72 parts of urea, 46 parts of ammonium chloride, 17 parts of potassium sulfate, 20 parts of monoammonium phosphate, 1.2 parts of sodium dodecylbenzene sulfonate, 2.6 parts of hydroxyethyl cellulose, 7 parts of sodium hydroxyethylidene diphosphonate, 0.4 parts of acetohydroxamic acid, 0.3 parts of 3,4-dimethylpyrazole phosphate, and 2 parts of synergist.

4. The method for drum granulation of water-soluble compound fertilizer according to claim 1, characterized in that: The method for preparing the water-soluble modified starch solution described in step (2) comprises the following steps: Step 1: dispersing and dissolving starch in water to prepare a starch emulsion with a mass percentage of 12.3% to 48.6%; Step 2: Add 3.2%-10.8% of vinyl acetate, 6.1%-14.5% of vinyl alcohol, 3.4%-8.2% of acrylic acid, 0.2%-0.4% of 2-acrylamido-2-methylpropanesulfonic acid, 0.1%-0.3% of sodium persulfate, 0.3%-0.5% of potassium bisulfite and 0.6%-1.4% of methylene succinic acid, 0.5%-1.2% of borax, and 0.1%-0.5% of potassium hydroxide aqueous solution to the starch emulsion prepared in step 1, and react for 0.5-1.2 hours under nitrogen protection to obtain starch emulsion a; Step 3, adding 0.008%-0.15% sodium acrylate, 0.002%-0.04% potassium hydroxide aqueous solution, 0.003%-0.26% sodium lauryl sulfate, 0.001%-0.03% p-hydroxycinnamic acid, 0.002%-0.046% p-hydroxybenzoic acid and 0.002%-0.028% aminoformic acid to the starch emulsion a prepared in step 2, and reacting for 1-1.5 hours under nitrogen protection to prepare starch emulsion b; Step 4: Add 0.003%-0.1% hydrochloric acid based on the dry weight of starch to the starch milk b prepared in step 3 to adjust the pH value of the solution to 5.6-6.2; Step 5, heating the starch milk b adjusted with pH value in step 4 to 65-94° C. and keeping the temperature for 2-4 hours under microwave power of 100-200 W in a sealed condition to obtain starch milk c; Step 6: heating the starch emulsion c obtained in step 5 at a pressure of 0.07-0.09 MPa to remove physically bound water at a heating temperature of 80-92° C. to obtain a water-soluble modified starch; Step 7: Disperse and dissolve the water-soluble modified starch obtained in step 6 in water to obtain a water-soluble modified starch solution.

5. The method for drum granulation of water-soluble compound fertilizer according to claim 4, characterized in that: The starch in step 1 is one or more of water-soluble corn starch, water-soluble sweet potato starch, water-soluble cassava starch, water-soluble wheat starch, water-soluble rice starch and water-soluble potato starch.

6. The method for drum granulation of water-soluble compound fertilizer according to claim 4, characterized in that: The water-soluble modified starch described in step seven is 1%-3% of the mass of the base fertilizer.

7. The method for drum granulation of water-soluble compound fertilizer according to claim 4, characterized in that: The mass concentration of the water-soluble modified starch solution in step seven is 32.6%-40.2%.

8. The method for drum granulation of water-soluble compound fertilizer according to claim 1, characterized in that: In step (4), the furnace head temperature of the drying drum is 180°C, and the furnace tail temperature is 60°C.

9. The method for drum granulation of water-soluble compound fertilizer according to claim 1, characterized in that: In step (6), the primary screening and the secondary screening use two sizes of screens respectively. The first size is 4.75 mm, which passes through particles larger than 4.75 and re-granulates them after being crushed. The second size is 1.00 mm, which directly re-granulates powders and small particles smaller than 1.00 mm.

10. The method for drum granulation of water-soluble compound fertilizer according to claim 1, characterized in that: The particle size of the qualified fertilizer granules in step (6) is 1.00-4.75 mm.

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