Ammonia-acid method compound fertilizer granulation process by adding urea formaldehyde

Abstract

The process comprises the following steps: S1, adding urea and a formaldehyde solution into a reaction kettle according to a molar ratio of 1: (1.8-2.2), then adding sodium hydroxide to adjust the pH value to 7.0, and carrying out a stirring reaction to generate a hydroxymethyl urea solution; adding sulfuric acid into the hydroxymethyl urea solution, adjusting the pH value to 4.5, and continuously stirring for reaction to obtain a urea formaldehyde solution; s2, weighing casein, glutamic acid, asparaginic acid and water in proportion, and uniformly mixing to obtain a synergistic solution; s3, weighing urea, monoammonium phosphate, potassium chloride, modified charcoal, polyethylene glycol and sodium carboxymethyl cellulose, and uniformly mixing to obtain a solid mixture; s4, putting the solid mixture into a rotary drum granulator, respectively spraying a urea formaldehyde solution and a synergist into a solid mixture bed through a granulation spray head, synchronously spraying liquid ammonia and sulfuric acid through a special spray head, and enabling the liquid ammonia and the sulfuric acid to generate a neutralization reaction on the surface of the solid mixture to obtain a compound fertilizer precursor; and S5, drying the compound fertilizer precursor to obtain the compound fertilizer.

Description

Technical Field

[0001] This invention relates to the field of compound fertilizer production technology, and in particular to a granulation process for amino acid-based compound fertilizer with added urea-formaldehyde. Background Technology

[0002] Compound fertilizers are essential agricultural inputs, widely used in crop fertilization due to their balanced nutrients and ease of application. The amino acid granulation method is a highly efficient, high-concentration compound fertilizer production technology. It primarily utilizes the neutralization reaction between ammonia and sulfuric acid within a granulator, instantly generating ammonium sulfate melt and releasing a large amount of heat. This melt acts as a liquid-phase binder, agglomerating solid powder into granules. This method offers advantages such as high pelleting rate, good particle strength, and reduced drying energy consumption through the utilization of reaction heat.

[0003] Currently, the nitrogen in compound fertilizers produced using the amino acid method on the market is mainly fast-acting ammonium nitrogen, which has problems such as easy volatilization, large leaching losses, and short fertilizer effect period, which can easily lead to crop nutrient deficiency in the later stages and environmental pollution.

[0004] Urea-formaldehyde, as an organic, slightly soluble, slow-release fertilizer, is an important slow-release nitrogen source. Its nitrogen needs to be gradually released through microbial decomposition, which can significantly improve nitrogen utilization.

[0005] However, directly applying urea-formaldehyde to the amino acid process presents the following technical problems: the high instantaneous temperature of the amino acid reaction may cause thermal decomposition of urea-formaldehyde, which can easily reduce the slow-release function and make it difficult to achieve controlled release of phosphorus and potassium nutrients; urea-formaldehyde is an organic compound, and its physical properties such as melting point and adhesiveness differ greatly from those of inorganic salts, making it relatively difficult to achieve uniform mixing and stable granulation with inorganic nutrients.

[0006] Therefore, providing a granulation process for compound fertilizer using the amino acid method with added urea-formaldehyde to solve the thermal stability problem of urea-formaldehyde under high-temperature amino acid reaction conditions, and producing compound fertilizer with high particle strength, excellent slow-release performance, and low caking is a technical problem that the industry urgently needs to solve. Summary of the Invention

[0007] The purpose of this invention is to provide a granulation process for amino acid-based compound fertilizers with added urea-formaldehyde, in order to solve the problems mentioned in the background art.

[0008] To achieve the above objectives, the present invention provides the following technical solution: a granulation process for amino acid-based compound fertilizer with added urea-formaldehyde, comprising the following steps: S1. Preparation of urea-formaldehyde solution: Urea and formaldehyde solution with a mass fraction of 38-40% are added to a reaction vessel at a molar ratio of 1:1.8-2.2. The mixture is heated to 55-60°C, and sodium hydroxide with a mass concentration of 11-12% is added to adjust the pH to 7.0. The mixture is stirred for 60-80 minutes to generate hydroxymethylurea solution. Sulfuric acid with a mass concentration of 12-15% is added to the hydroxymethylurea solution to adjust the pH to 4.5. The mixture is stirred for another 50-60 minutes to obtain urea-formaldehyde solution.

[0009] S2. Preparation of synergistic solution: Weigh 10-12 parts by weight of casein, 5-8 parts by weight of glutamic acid, 2-4 parts by weight of aspartic acid, and 40-45 parts by weight of water, mix them evenly to obtain the synergistic solution.

[0010] S3. Solid mixture mixing: Weigh 25-30 parts by weight of urea, 15-18 parts by weight of monoammonium phosphate, 8-10 parts by weight of potassium chloride, 3-5 parts by weight of modified biochar, 2-4 parts by weight of polyethylene glycol, and 1-3 parts by weight of sodium carboxymethyl cellulose, and mix them evenly to obtain a solid mixture.

[0011] S4. Amino acid granulation: The solid mixture is placed into a rotary drum granulator. The conveying pump and nozzle are started, and the urea-formaldehyde solution and synergist are sprayed into the solid mixture bed through the granulation nozzle. Liquid ammonia and sulfuric acid are sprayed in simultaneously through a special nozzle, so that the liquid ammonia and sulfuric acid can undergo a neutralization reaction on the surface of the solid mixture, promoting the rolling, agglomeration and bonding of the material into granules, and obtaining a compound fertilizer precursor with a particle size of 3-5mm.

[0012] S5. Drying: The compound fertilizer precursor is placed in a hot air dryer at 90-100℃ to dry, and a compound fertilizer with a moisture content of less than 1.5% is obtained.

[0013] As a preferred embodiment of the present invention, in step S4, the amount of liquid ammonia added is 1.0 to 1.2% of the mass of the solid mixture, the molar ratio of liquid ammonia to sulfuric acid is 1.5 to 1.8:1, the volume concentration of liquid ammonia is 80 to 85%, and the volume concentration of sulfuric acid is 45 to 50%.

[0014] As a preferred embodiment of the present invention, the neutralization reaction temperature in S4 is 75-85°C.

[0015] As a preferred embodiment of the present invention, the amount of urea-formaldehyde solution added in S4 is 12-15% of the mass of the solid mixture.

[0016] As a preferred embodiment of the present invention, the amount of synergistic liquid added in S4 is 8-12% of the mass of the solid mixture.

[0017] As a preferred embodiment of the present invention, the rotational speed of the rotary drum granulator is 25-30 rpm.

[0018] As a preferred embodiment of the present invention, the modified biochar is prepared by the following method: Step 1: Biochar preparation: Dry straw and bamboo until the moisture content is 8-12%. Crush the dried straw and bamboo separately in a crusher to obtain 60-100 mesh powder. Then mix them at a mass ratio of 2:1 and place them in a carbonization furnace to carbonize at 500-520℃ for 1.5-2 hours to obtain biochar.

[0019] Step 2, Biochar Modification: Weigh 35-40 parts by weight of biochar, 3-4 parts by weight of nano titanium dioxide, 1-2 parts by weight of polyethylene glycol, and 50-55 parts by weight of water, place them in an ultrasonic device for 15-20 minutes, filter, and dry to obtain modified biochar.

[0020] As a preferred embodiment of the present invention, the ultrasonic device has a temperature of 45-50°C and a frequency of 80-85 kHz.

[0021] Compared with the prior art, the beneficial effects of the present invention are: 1. This invention deeply integrates the urea-formaldehyde synthesis process with the amino acid granulation process, and simultaneously completes urea-formaldehyde spraying, liquid ammonia neutralization and particle agglomeration in a rotary drum granulator. This breaks through the limitations of the segmented operation of traditional processes. The introduction of urea-formaldehyde not only provides a slow-release nitrogen source, but its high molecular organic properties also act as a natural binder. In synergy with the ammonium sulfate melt, it significantly improves the strength of the finished particles and effectively reduces the tendency of the product to clump.

[0022] 2. This invention involves carbonizing a mixture of straw and bamboo under high temperature conditions, then adding nano-titanium dioxide and polyethylene glycol for modification in a plasma device to obtain modified biochar. The modified biochar possesses a porous structure and a large specific surface area. The photocatalytic activity of titanium dioxide and the dispersing and water-retaining properties of polyethylene glycol, combined with ultrasonic modification, further enhance the biochar's adsorption, slow release, and activation effects on compound fertilizer nutrients, achieving efficient nutrient utilization. Ultrasonic action allows nano-titanium dioxide to be uniformly loaded within the biochar pores, forming a composite adsorption layer. The positively charged surface of the nano-titanium dioxide can adsorb phosphate ions (PO4) from the compound fertilizer through electrostatic interactions. 3- ), sulfate (SO4 2- Anionic nutrients such as phosphorus and sulfur are introduced, reducing leaching losses. Polyethylene glycol, as a polymeric dispersant, can form a hydrophilic film on the surface of biochar, which can slow down the erosion of nutrients by water. Moreover, it can control and regulate the nitrogen release rate through membrane permeation, avoiding the phenomenon of "early seedling burn and later nutrient deficiency".

[0023] 3. By precisely controlling the molar ratio of the amino acid reaction and the temperature of the reaction zone in the granulator (75-85℃), this invention ensures that the amino acid reaction provides sufficient liquid phase and heat for granulation, while avoiding excessive temperature that could lead to the decomposition and failure of urea-formaldehyde. By introducing heat-sensitive urea-formaldehyde into the amino acid process, the slow-release effect and fertilizer efficiency of compound fertilizer are improved.

[0024] 4. This invention incorporates casein, glutamic acid, and aspartic acid during the preparation of the synergistic solution, thereby improving the fertilizer efficiency of the compound fertilizer. Casein dissolves in water to form a colloidal solution. Its polymer chains can encapsulate the solid raw materials of the compound fertilizer through hydrogen bonds and van der Waals forces, filling the internal voids of the particles and enhancing their bonding strength and compressive strength. Simultaneously, the good flowability of the casein colloid allows it to evenly cover the surface of the raw materials during granulation. Combined with the rolling action of the drum, this results in more regular spherical particles. Furthermore, the positively charged amino groups in the casein molecules can adsorb phosphate ions (PO4) from the compound fertilizer through electrostatic interactions. 3- ), sulfate (SO4 2- Anionic nutrients, such as casein, can adsorb K+ by the negatively charged carboxyl groups in casein molecules. + NH4 + Cationic nutrients enhance the slow-release regulation effect of compound fertilizers, thereby improving the fertilizer efficiency of compound fertilizers.

[0025] 5. This invention adds sodium carboxymethyl cellulose to the compound fertilizer. The anionic carboxymethyl groups of sodium carboxymethyl cellulose can be adsorbed on the surface of the solid raw materials of the compound fertilizer, forming "steric hindrance" to prevent the raw material particles from agglomerating. The hydrophilic carboxyl groups in the sodium carboxymethyl cellulose molecule can form hydrogen bonds with soil particles, enhancing soil water retention and reducing nutrient loss caused by rainwater erosion. Attached Figure Description

[0026] Figure 1 This is a flow chart of the granulation process for the amino acid-based compound fertilizer with added urea-formaldehyde, as described in this invention. Detailed Implementation

[0027] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0028] like Figure 1 As shown, a granulation process for amino acid-based compound fertilizer with added urea-formaldehyde includes the following steps: S1. Preparation of Urea-Formaldehyde Solution: Add urea and formaldehyde solution to a reaction vessel at a molar ratio of 1:1.8-2.2, heat to 55-60℃, then add sodium hydroxide to adjust the pH to 7.0, stir for 60-80 min to generate hydroxymethylurea solution; add sulfuric acid to the hydroxymethylurea solution to adjust the pH to 4.5, continue stirring for 50-60 min to obtain urea-formaldehyde solution. S2. Preparation of Synergistic Solution: Weigh casein, glutamic acid, aspartic acid, and water according to the proportions, mix thoroughly to obtain the synergistic solution. S3. Mixing of Solid Mixture: Weigh urea, monoammonium phosphate, potassium chloride, modified biochar, polyethylene glycol, and sodium carboxymethyl cellulose, mix thoroughly to obtain the solid mixture. S4. Acid Granulation: The solid mixture is placed into a rotary drum granulator. The conveying pump and nozzles are started, and urea-formaldehyde solution and synergist are sprayed into the solid mixture bed through the granulation nozzles. Liquid ammonia and sulfuric acid are sprayed in simultaneously through special nozzles, causing the liquid ammonia and sulfuric acid to neutralize on the surface of the solid mixture, promoting the rolling, agglomeration, and granulation of the material to obtain a compound fertilizer precursor with a particle size of 3-5 mm. S5. Drying: The compound fertilizer precursor is placed in a hot air dryer at 90-100℃ to dry, obtaining a compound fertilizer with a moisture content of less than 1.5%.

[0029] All raw materials used in this invention are commercially available.

[0030] Example 1

[0031] A granulation process for amino acid-based compound fertilizer with added urea-formaldehyde, characterized by comprising the following steps: S1. Preparation of urea-formaldehyde solution: Urea and 38% formaldehyde solution were added to a reaction vessel at a molar ratio of 1:1.8, heated to 55°C, and then 11% sodium hydroxide was added to adjust the pH to 7.0. The mixture was stirred for 60 min to generate hydroxymethylurea solution. 12% sulfuric acid was added to the hydroxymethylurea solution to adjust the pH to 4.5, and the mixture was stirred for another 50 min to obtain urea-formaldehyde solution.

[0032] S2. Preparation of synergistic solution: Weigh 10 parts by weight of casein, 5 parts by weight of glutamic acid, 2 parts by weight of aspartic acid, and 40 parts by weight of water, mix them evenly to obtain the synergistic solution.

[0033] S3. (1) Preparation of modified biochar: Straw and bamboo are dried to a moisture content of 8%. The dried straw and bamboo are crushed in a pulverizer to obtain 60-100 mesh pulverized material. Then, they are mixed at a mass ratio of 2:1 and placed in a carbonization furnace at 500℃ for 2 hours to obtain biochar. 35 parts by weight of biochar, 3 parts by weight of nano titanium dioxide, 1 part by weight of polyethylene glycol, and 50 parts by weight of water are placed in an ultrasonic device at a temperature of 45℃ and a frequency of 80KHz for 20 minutes, then filtered and dried to obtain modified biochar. (2) Mixing of solid mixture: 25 parts by weight of urea, 15-18 parts by weight of monoammonium phosphate, 8 parts by weight of potassium chloride, 3 parts by weight of modified biochar, 2 parts by weight of polyethylene glycol, and 1 part by weight of sodium carboxymethyl cellulose are mixed evenly to obtain solid mixture.

[0034] S4. Amino Acid Granulation: The solid mixture is placed in a rotary drum granulator with a rotation speed of 25 rpm. The conveying pump and nozzle are started, and urea-formaldehyde solution and synergist are sprayed into the solid mixture bed through the granulation nozzle. Liquid ammonia and sulfuric acid are sprayed in simultaneously through a special nozzle, so that liquid ammonia (volume concentration of 80%) and sulfuric acid (volume concentration of 45%) undergo a neutralization reaction on the surface of the solid mixture at a temperature of 75℃, which promotes the rolling, agglomeration and bonding of materials into granules, resulting in a compound fertilizer precursor with a particle size of 3-5 mm. The amount of urea-formaldehyde solution added is 12% of the mass of the solid mixture, the amount of synergist added is 8% of the mass of the solid mixture, the amount of liquid ammonia added is 1.0% of the mass of the solid mixture, and the molar ratio of liquid ammonia to sulfuric acid is 1.5:1.

[0035] S5. Drying: The compound fertilizer precursor is placed in a hot air dryer at 90℃ to dry, and a compound fertilizer with a moisture content of 1.5% is obtained.

[0036] Example 2

[0037] A granulation process for amino acid-based compound fertilizer with added urea-formaldehyde, characterized by comprising the following steps: S1. Preparation of urea-formaldehyde solution: Urea and 40% formaldehyde solution were added to a reaction vessel at a molar ratio of 1:2.2, heated to 60°C, and then 12% sodium hydroxide was added to adjust the pH to 7.0. The mixture was stirred for 80 min to generate hydroxymethylurea solution. 15% sulfuric acid was added to the hydroxymethylurea solution to adjust the pH to 4.5, and the mixture was stirred for another 60 min to obtain urea-formaldehyde solution.

[0038] S2. Preparation of synergistic solution: Weigh 12 parts by weight of casein, 8 parts by weight of glutamic acid, 4 parts by weight of aspartic acid, and 45 parts by weight of water, mix them evenly to obtain the synergistic solution.

[0039] S3. (1) Preparation of modified biochar: Straw and bamboo are dried to a moisture content of 12%. The dried straw and bamboo are crushed in a pulverizer to obtain 60-100 mesh pulverized material. Then, they are mixed at a mass ratio of 2:1 and placed in a carbonization furnace for carbonization at 520℃ for 1.5h to obtain biochar. 40 parts by weight of biochar, 4 parts by weight of nano titanium dioxide, 2 parts by weight of polyethylene glycol and 55 parts by weight of water are weighed and placed in an ultrasonic device at a temperature of 50℃ and a frequency of 85KHz for 15min. After filtration and drying, modified biochar is obtained. (2) Mixing of solid mixture: 30 parts by weight of urea, 18 parts by weight of monoammonium phosphate, 10 parts by weight of potassium chloride, 5 parts by weight of modified biochar, 4 parts by weight of polyethylene glycol and 3 parts by weight of sodium carboxymethyl cellulose are weighed and mixed evenly to obtain solid mixture.

[0040] S4. Amino Acid Granulation: The solid mixture is placed in a rotary drum granulator with a rotation speed of 30 rpm. The conveying pump and nozzle are started, and the urea-formaldehyde solution and synergist are sprayed into the solid mixture bed through the granulation nozzle. Liquid ammonia and sulfuric acid are sprayed in simultaneously through a special nozzle, so that the liquid ammonia (volume concentration of 85%) and sulfuric acid (volume concentration of 50%) undergo a neutralization reaction on the surface of the solid mixture at a temperature of 85℃, which promotes the rolling, agglomeration and bonding of the material into granules, resulting in a compound fertilizer precursor with a particle size of 3-5 mm. The amount of urea-formaldehyde solution added is 15% of the mass of the solid mixture, the amount of synergist added is 12% of the mass of the solid mixture, the amount of liquid ammonia added is 1.2% of the mass of the solid mixture, and the molar ratio of liquid ammonia to sulfuric acid is 1.8:1.

[0041] S5. Drying: The compound fertilizer precursor is placed in a hot air dryer at 90-100℃ to dry, and a compound fertilizer with a moisture content of 1.2% is obtained.

[0042] Example 3

[0043] A granulation process for amino acid-based compound fertilizer with added urea-formaldehyde, characterized by comprising the following steps: S1. Preparation of urea-formaldehyde solution: Urea and 40% formaldehyde solution were added to a reaction vessel at a molar ratio of 1:2.0, heated to 56°C, and then 11.5% sodium hydroxide was added to adjust the pH to 7.0. The mixture was stirred for 70 min to generate hydroxymethylurea solution. 13% sulfuric acid was added to the hydroxymethylurea solution to adjust the pH to 4.5, and the mixture was stirred for another 55 min to obtain urea-formaldehyde solution.

[0044] S2. Preparation of synergistic solution: Weigh 11 parts by weight of casein, 6 parts by weight of glutamic acid, 3 parts by weight of aspartic acid, and 42 parts by weight of water, mix them evenly to obtain the synergistic solution.

[0045] S3. (1) Preparation of modified biochar: Straw and bamboo are dried to a moisture content of 10%. The dried straw and bamboo are crushed in a pulverizer to obtain 60-100 mesh pulverized material. Then, they are mixed at a mass ratio of 2:1 and placed in a carbonization furnace for carbonization at 510℃ for 1.5h to obtain biochar. 36 parts by weight of biochar, 3.5 parts by weight of nano titanium dioxide, 1.5 parts by weight of polyethylene glycol and 52 parts by weight of water are weighed and placed in an ultrasonic device at a temperature of 48℃ and a frequency of 80KHz for 18min. After filtration and drying, modified biochar is obtained. (2) Mixing of solid mixture: 28 parts by weight of urea, 16 parts by weight of monoammonium phosphate, 9 parts by weight of potassium chloride, 4 parts by weight of modified biochar, 3 parts by weight of polyethylene glycol and 2 parts by weight of sodium carboxymethyl cellulose are weighed and mixed evenly to obtain solid mixture.

[0046] S4. Amino Acid Granulation: The solid mixture is placed in a rotary drum granulator with a rotation speed of 28 rpm. The conveying pump and nozzle are started, and the urea-formaldehyde solution and synergist are sprayed into the solid mixture bed through the granulation nozzle. Liquid ammonia and sulfuric acid are sprayed in simultaneously through a special nozzle, so that the liquid ammonia (volume concentration of 82%) and sulfuric acid (volume concentration of 48%) undergo a neutralization reaction on the surface of the solid mixture at a temperature of 80℃, which promotes the rolling, agglomeration and bonding of the material into granules, resulting in a compound fertilizer precursor with a particle size of 3-5 mm. The amount of urea-formaldehyde solution added is 13% of the mass of the solid mixture, the amount of synergist added is 10% of the mass of the solid mixture, the amount of liquid ammonia added is 1.1% of the mass of the solid mixture, and the molar ratio of liquid ammonia to sulfuric acid is 1.6:1.

[0047] S5. Drying: The compound fertilizer precursor is placed in a hot air dryer at 95℃ to dry, and a compound fertilizer with a moisture content of 1.3% is obtained.

[0048] Comparative Example 1: The difference from Example 1 is that the modified biochar is removed.

[0049] Comparative Example 2: The difference from Example 1 is that urea-formaldehyde is removed.

[0050] Comparative Example 3: The difference from Example 1 is that casein is removed.

[0051] Comparative Example 4: The difference from Example 1 is that sodium carboxymethyl cellulose is removed.

[0052] The effects of the compound fertilizers prepared in Examples 1, 2, and 3 and Comparative Examples 1, 2, 3, and 4 were verified.

[0053] At the wheat experimental base, fertilization was carried out 8-10 days after the wheat seedlings emerged, with an application rate of 45-50 kg per mu (approximately 0.067 hectares) of fertilizer. The wheat yield after harvest was measured. One month after fertilization, the nitrogen, phosphorus, potassium, and organic matter content in the soil was measured. The control group was not fertilized. The detection methods were as follows: the organic matter in the soil was detected using NY / T 1121.6-2006 "Soil Testing", and the nitrogen, phosphorus, and potassium content in the soil was determined by liquid chromatography. The results are shown in Table 1.

[0054] Table 1:

[0055] As shown in Table 1, the compound fertilizer prepared in the examples had higher wheat yield per mu and higher nitrogen, phosphorus, potassium, and organic matter content in the soil than the comparative examples and the control group. The wheat yield per mu of the compound fertilizer applied to comparative examples 1, 2, 3, 4, and the control group was 5.4%, 7.1%, 9.0%, 3.6%, and 14.2% lower than that of example 1, respectively.

[0056] Modified biochar was obtained by modifying nano-titanium dioxide and polyethylene glycol in a plasma device. The modified biochar possesses a porous structure and a large specific surface area. The photocatalytic activity of titanium dioxide and the dispersing and water-retaining properties of polyethylene glycol, combined with ultrasonic modification, further enhance the biochar's adsorption, slow release, and activation effects on compound fertilizer nutrients, achieving efficient nutrient utilization. The positively charged amino groups in casein molecules can adsorb phosphate ions (PO4) from compound fertilizer through electrostatic interactions. 3- ), sulfate (SO4 2- Anionic nutrients, such as casein, can adsorb K+ by the negatively charged carboxyl groups in casein molecules. + NH4 + Cationic nutrients enhance the slow-release regulation effect of compound fertilizers, thereby improving their fertilizer efficiency. The introduction of urea-formaldehyde not only provides a slow-release nitrogen source, but its high molecular weight organic properties also act as a natural binder, synergistically improving the strength of the finished granules and effectively reducing the tendency for clumping. The hydrophilic carboxyl groups in sodium carboxymethyl cellulose molecules can form hydrogen bonds with soil particles, enhancing soil water retention and reducing nutrient loss due to rainwater runoff.

[0057] In summary, the granulation process of compound fertilizer using urea-formaldehyde with added amino acids of the present invention can solve the problem of thermal stability of urea-formaldehyde under high-temperature amino acid reaction conditions, producing compound fertilizer with high granule strength, excellent slow-release performance, and is not prone to caking. Moreover, the compound fertilizer has high fertilizer efficiency, the process is simple, and it is suitable for large-scale production.

[0058] The above are merely specific embodiments of the present invention, but the technical features of the present invention are not limited thereto. Any simple changes, equivalent substitutions, or modifications made based on the present invention to solve essentially the same technical problems and achieve essentially the same technical effects are all covered within the protection scope of the present invention.

Claims

1. A urea-formaldehyde added ammoniacal method compound fertilizer granulation process, characterized in that, The method comprises the following steps: S1. Urea-formaldehyde solution preparation: urea and formaldehyde solution with mass fraction of 38-40% are added into a reaction kettle according to a molar ratio of 1:1.8-2.2, heated to 55-60 DEG C, then sodium hydroxide with mass concentration of 11-12% is added to adjust the pH value to 7.0, stirred for 60-80 min to generate a methylol urea solution; sulfuric acid with mass concentration of 12-15% is added to the methylol urea solution to adjust the pH value to 4.5, and the stirring reaction is continued for 50-60 min to obtain a urea-formaldehyde solution; S2. Synergistic liquid preparation: casein 10-12 parts by weight, glutamic acid 5-8 parts by weight, aspartic acid 2-4 parts by weight, and water 40-45 parts by weight are mixed to obtain a synergistic liquid; S3. Solid mixture mixing: urea 25-30 parts by weight, monoammonium phosphate 15-18 parts by weight, potassium chloride 8-10 parts by weight, modified biochar 3-5 parts by weight, polyethylene glycol 2-4 parts by weight, and sodium carboxymethyl cellulose 1-3 parts by weight are mixed to obtain a solid mixture; S4. Ammonia acid granulation: the solid mixture is placed into a rotary drum granulator, a conveying pump and a nozzle are started, the urea-formaldehyde solution and the synergistic agent are sprayed onto the solid mixture bed through the granulation nozzle, liquid ammonia and sulfuric acid are synchronously sprayed through a special nozzle, the neutralization reaction of liquid ammonia and sulfuric acid occurs on the surface of the solid mixture, the material is promoted to roll, agglomerate and bond to form granules, and a compound fertilizer precursor with a particle size of 3-5 mm is obtained; S5. Drying: the compound fertilizer precursor is placed into a hot air dryer at 90-100 DEG C to obtain a compound fertilizer with a water content of less than 1.5%.

2. The urea-formaldehyde-added ammoniacal method compound fertilizer granulation process according to claim 1, characterized in that, In S4, the addition amount of liquid ammonia is 1.0-1.2% of the mass of the solid mixture, the molar ratio of liquid ammonia to sulfuric acid is 1.5-1.8:1, the volume concentration of liquid ammonia is 80-85%, and the volume concentration of sulfuric acid is 45-50%.

3. The urea-formaldehyde-added ammoniacal method compound fertilizer granulation process according to claim 1, characterized in that, The neutralization reaction temperature in S4 is 75-85 DEG C.

4. The urea-formaldehyde-added ammoniacal method compound fertilizer granulation process according to claim 1, characterized in that, The addition amount of urea-formaldehyde solution in S4 is 12-15% of the mass of the solid mixture.

5. The urea-formaldehyde-added ammoniacal method compound fertilizer granulation process according to claim 1, characterized in that, The addition amount of synergistic liquid in S4 is 8-12% of the mass of the solid mixture.

6. The urea-formaldehyde-added ammoniacal method compound fertilizer granulation process according to claim 1, characterized in that, The rotating speed of the rotary drum granulator is 25-30 rpm.

7. The urea-formaldehyde-added ammoniacal method compound fertilizer granulation process according to claim 1, characterized by, The modified biochar is prepared by the following method: Step one, biochar preparation: straw and bamboo are dried to a moisture content of 8-12%, the dried straw and bamboo are respectively crushed in a crusher to obtain crushed materials with a particle size of 60-100 mesh, then the crushed materials are mixed according to a mass ratio of 2:1, and then placed in a carbonization furnace for carbonization at 500-520 DEG C for 1.5-2 h to obtain biochar; Step two, biochar modification: biochar 35-40 parts by weight, nano-titanium dioxide 3-4 parts by weight, polyethylene glycol 1-2 parts by weight, and water 50-55 parts by weight are placed in an ultrasonic device for treatment for 15-20 min, then filtered and dried to obtain modified biochar.

8. The urea-formaldehyde-added ammoniacal method compound fertilizer granulation process according to claim 7, characterized by, The temperature of the ultrasonic device is 45-50 DEG C, and the frequency is 80-85 KHz.

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