Method for preparing high-nitrogen humic acid liquid fertilizer

Abstract

The present application relates to the technical field of agricultural fertilizer production, and discloses a method for manufacturing high-nitrogen humic acid liquid fertilizer, comprising the following steps: S1, selecting raw materials, a reaction promoting system and auxiliary components, wherein the raw materials comprise lignite, a composite nitrogen source, an alkaline activator and an acid regulator, the reaction promoting system comprises an ionic liquid dispersant and a metal ion catalyst, and the auxiliary components comprise modified chitosan flocculants, amino silane coupling agents and deionized water; S2, the lignite is crushed and ground in sequence, and then mixed and stirred with the deionized water and the ionic liquid dispersant to form a humic acid suspension. The dispersibility of the humic acid is improved by the ionic liquid dispersant, the mass transfer is assisted by low-frequency ultrasound, and the reaction sites of the humic acid, the nitrogen source and the activator are fully contacted by using a segmented temperature control catalytic process, and meanwhile, the double-pipe precise injection technology avoids local reaction imbalance, shortens the reaction period, and is more efficient than the traditional step-by-step reaction process.

Description

Technical Field

[0001] This invention relates to the field of agricultural fertilizer production technology, specifically a method for producing high-nitrogen humic acid liquid fertilizer. Background Technology

[0002] Liquid fertilizer is a fertilizer product existing in liquid form. Its nutrients are uniformly dissolved and can be applied through drip irrigation, sprinkler irrigation, fertigation, etc. It can be quickly absorbed and utilized by crop roots, reducing nutrient loss. Its convenient application and suitability for the needs of modern large-scale agricultural planting have made it one of the important development directions in the fertilizer field. Nitrogen is a core nutrient element required for crop growth and development, directly affecting crop foliage growth, photosynthetic efficiency, and yield. Humic acid has properties that improve soil structure, promote nutrient adsorption and fixation, and enhance crop resistance. High-nitrogen humic acid liquid fertilizer, prepared by combining high-nitrogen sources with humic acid, can provide crops with sufficient nitrogen nutrition while improving fertilizer utilization through the synergistic effect of humic acid, meeting the urgent need of modern agriculture for efficient and high-quality fertilizers.

[0003] Currently, high-nitrogen humic acid liquid fertilizer is produced by pretreating humic acid raw materials using crushers and ball mills, then mixing the humic acid with a nitrogen source, alkaline activator, and acid regulator in a reaction vessel. The reaction system is controlled by stepwise injection of the acid-base activator, combined with conventional mechanical stirring to achieve mass transfer and reaction. Finally, the finished product is obtained through separation and filtration. However, in practice, humic acid molecules exhibit strong intermolecular aggregation and poor natural dispersion. Furthermore, stepwise injection of the acid-base activator can easily lead to local pH imbalances, making it difficult for the humic acid to fully contact the reaction sites with the nitrogen source and activator. This results in a prolonged reaction cycle and low overall process efficiency. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a method for producing high-nitrogen humic acid liquid fertilizer, which solves the problems of strong intermolecular aggregation of humic acid, poor natural dispersion, and difficulty in fully contacting the reaction sites of nitrogen sources and activators, resulting in prolonged reaction cycles and low overall process efficiency.

[0005] To achieve the above objectives, the present invention provides a method for producing a high-nitrogen humic acid liquid fertilizer, comprising the following steps: S1. Select raw materials, reaction promotion system and auxiliary components. The raw materials include lignite, composite nitrogen source, alkaline activator and acid regulator. The reaction promotion system includes ionic liquid dispersant and metal ion catalyst. The auxiliary components include modified chitosan flocculant, aminosilane coupling agent and deionized water. S2. After the lignite is crushed and ground in sequence, it is mixed with deionized water and ionic liquid dispersant to form a humic acid suspension. S3. Transfer the humic acid suspension into the reactor, and simultaneously inject the alkaline activator and acid regulator through the dual-pipe precision injection device. Turn on the ultrasonic-assisted mass transfer and maintain the reaction temperature through the steam in the outer pipe. S4. Add a composite nitrogen source and a metal ion catalyst to the system in step S3, and carry out the catalytic composite reaction in two stages. The temperature is maintained stable in both stages by steam in the outer tube. S5. Add modified chitosan flocculant to the material in step S4, stir, then transfer to a centrifuge for separation and collect the refined filtrate. S6. After filtering the high-quality filtrate, add aminosilane coupling agent and stir to complete the secondary stabilization of the system; S7. After cooling the material from step S6 to room temperature, it is pressure-stabilized in a high-level buffer tank and then transported to the filling port by a circulating pump to complete the filling.

[0006] By employing the above technical solution, lignite is sequentially crushed and ground to increase its specific surface area. It is then mixed with deionized water and an ionic liquid dispersant. The ionic liquid dispersant reduces the intermolecular forces of humic acid, ensuring uniform dispersion of humic acid in the water and forming a stable humic acid suspension, thus creating contact conditions for a complete reaction. The humic acid suspension is transferred to a reaction vessel, where an alkaline activator and an acidic regulator are simultaneously injected through a dual-pipe precision injection device. This ensures uniform distribution of the two reagents in the system, preventing localized concentration imbalances. Ultrasonic-assisted mass transfer accelerates molecular motion and increases the contact probability at reaction sites. Steam in the external pipe maintains a stable reaction temperature, ensuring constant reaction kinetics. A composite nitrogen source and a metal ion catalyst are added to the system, initiating a two-stage catalytic composite reaction with appropriate reaction environments at each stage. The process involves combining a composite nitrogen source with humic acid, using a metal ion catalyst to lower the activation energy of the reaction, and continuously maintaining a stable temperature with steam in the external pipe to ensure the reaction proceeds according to the preset extent. Modified chitosan flocculant is added to the material and stirred; this flocculant selectively adsorbs impurity particles in the system, causing them to aggregate and form flocs, which are then separated in a centrifuge, achieving efficient separation of impurities from the refined filtrate and reducing the loss of effective components with the filter residue. The refined filtrate is then filtered to remove trace suspended impurities, improving its purity. An aminosilane coupling agent is added and stirred; the aminosilane coupling agent interacts with the humic acid-nitrogen complex, enhancing the structural stability of the complex and completing secondary stabilization of the system. After cooling the material to room temperature, it is maintained at a stable pressure in a high-level buffer tank and smoothly transported to the filling port via a circulating pump, ensuring continuous and uniform filling, ultimately completing the finished product filling.

[0007] Preferably, in step S1, the raw materials consist of 10.0-15.0 parts by weight of lignite, 20.0-25.0 parts by weight of composite nitrogen source, 3.0-5.0 parts by weight of alkaline activator, and 2.0-4.0 parts by weight of acidic regulator; the reaction promotion system consists of 0.5-1.0 parts by weight of ionic liquid dispersant and 0.1-0.3 parts by weight of metal ion catalyst; and the auxiliary components consist of 0.2-0.5 parts by weight of modified chitosan flocculant, 0.05-0.1 parts by weight of aminosilane coupling agent, and 45.0-55.0 parts by weight of deionized water.

[0008] By adopting the above technical solution, lignite provides the basic component of humic acid for the reaction, the composite nitrogen source provides nitrogen for the product, and the alkaline activator and acid regulator can adjust the pH of the reaction system, creating a suitable chemical environment for the combination of humic acid and nitrogen source. The reaction promotion system consists of an ionic liquid dispersant and a metal ion catalyst. The ionic liquid dispersant can reduce the intermolecular aggregation force of humic acid, so that humic acid is evenly distributed in the reaction system and increases the contact area between humic acid and other reaction components. The metal ion catalyst can reduce the activation energy required for the reaction and promote the reaction process. The auxiliary components consist of modified chitosan flocculant, aminosilane coupling agent and deionized water. Deionized water serves as the reaction medium, providing a carrier for the mixing and reaction of various components. The modified chitosan flocculant can selectively adsorb impurity particles generated during the reaction, reducing the loss of effective components with impurities. The aminosilane coupling agent can interact with the humic acid-nitrogen complex, enhancing the structural integrity of the complex. Each component is matched according to its corresponding category.

[0009] Preferably, the composite nitrogen source is composed of urea and hydroxymethylurea in a weight ratio of 1:0.3, the alkaline activator is composed of potassium hydroxide and potassium carbonate in a weight ratio of 2:1, the ionic liquid dispersant is 1-butyl-3-methylimidazolium acetate, and the metal ion catalyst is anhydrous zinc chloride.

[0010] By adopting the above technical solution, the composite nitrogen source is a combination of urea and hydroxymethylurea. The molecular structure characteristics of the two enable them to form a multi-component combination with the carboxyl and hydroxyl groups of humic acid, enhancing the structural integrity after combination. The alkaline activator is a combination of potassium hydroxide and potassium carbonate. The dissociation characteristics of the two alkaline substances can synergistically regulate the pH of the reaction system, avoiding local pH fluctuations caused by a single alkaline substance, and providing a stable chemical environment for the complexation reaction of humic acid and nitrogen source. The ionic liquid dispersant 1-butyl-3-methylimidazolium acetate has a special molecular structure, which can reduce the aggregation force between humic acid molecules, so that humic acid is uniformly dispersed in the reaction medium and increases the contact sites between humic acid and other reaction components. The metal ion catalyst anhydrous zinc chloride can provide catalytic active centers, reduce the activation energy of the combination reaction of humic acid and nitrogen source, promote the reaction process, and its residual ions can also interact with aminosilane coupling agents to further enhance the structural stability of humic acid-nitrogen complex.

[0011] Preferably, the modified chitosan flocculant is chitosan modified with glycidyltrimethylammonium chloride, with a molecular weight of 100,000~300,000 Da, and the aminosilane coupling agent is 3-aminopropyltriethoxysilane.

[0012] By adopting the above technical solution, chitosan modified with glycidyltrimethylammonium chloride is used as a modified chitosan flocculant. The quaternary ammonium groups introduced into its molecular structure can enhance the adsorption selectivity of impurity particles in the reaction system, and can specifically bind impurities to form easily separable flocs, thereby achieving precise separation of impurities and effective components and reducing the loss of effective components with filter residue. 3-aminopropyltriethoxysilane is used as an aminosilane coupling agent. The amino and alkoxy groups in its molecule can interact with the residual metal ion catalyst and humic acid-nitrogen complex respectively to form a stable chemical bond structure, improve the structural integrity of humic acid-nitrogen complex, avoid precipitation and stratification during storage, and reduce nitrogen loss.

[0013] Preferably, in step S2, the lignite is crushed to a particle size of 60-80 mesh by a jaw crusher, and then ground to a particle size of 80-100 mesh by a planetary ball mill. The grinding speed is 300-400 r / min and the grinding time is 30-40 min. When mixing with deionized water and ionic liquid dispersant, the stirring speed is 500~600 r / min, the stirring temperature is 28~32℃, and the stirring time is 8~12 min.

[0014] By adopting the above technical solution, lignite is crushed by a jaw crusher and then ground by a planetary ball mill to gradually reduce the particle size of lignite and increase its specific surface area, so that more of the humic acid contained in lignite is exposed in the reaction system. Subsequently, the treated lignite is mixed with deionized water and ionic liquid dispersant. The stirring operation can accelerate the mixing process between the components. Combined with the characteristics of ionic liquid dispersant, it breaks the aggregation state between humic acid molecules, so that humic acid is evenly distributed in deionized water, increasing the probability of contact between humic acid and nitrogen source and activator in subsequent reactions, and providing a structural basis for the full action of each reaction component.

[0015] Preferably, in step S3, when using ultrasonic assistance, the frequency is 20kHz~22kHz, the power is 140~160W, the reaction temperature is 60~65℃, the reaction time is 8~12min, and the stirring speed of the reactor is 400~500r / min.

[0016] By adopting the above technical solution, when ultrasound assists the reaction system, it promotes molecular motion within the system, enhances the mass transfer process, and ensures that the reaction sites of humic acid, alkaline activator, and acid regulator are in full contact. The stirring operation of the reaction vessel can make the components in the system evenly distributed, avoid the imbalance of reagent concentration in local areas, and further improve the mass transfer efficiency in conjunction with ultrasound assistance, ensuring that the reaction process is completed within the set time.

[0017] Preferably, step S4 consists of two stages as follows: The first stage is carried out at a temperature of 58~62℃, an ultrasonic power of 140~160W, a stirring speed of 400~500r / min, and a reaction time of 4~6min. In the second stage, the temperature is raised to 63~67℃, and the reaction is continued for 10~15 minutes with an ultrasonic power of 190~210W and a stirring speed of 500~600r / min.

[0018] By adopting the above technical solution, the combination of temperature, ultrasonic power, and stirring speed in the first stage provides a suitable environment for the initial action of the composite nitrogen source, metal ion catalyst, and system. Ultrasonic assistance enhances mass transfer, and stirring ensures uniform distribution of each component, promoting the initiation of the initial combination reaction between humic acid and nitrogen source. In the second stage, the temperature is increased, ultrasonic power is improved, and stirring speed is increased to further accelerate the molecular motion rate, improve mass transfer efficiency, enhance the catalytic effect of metal ion catalyst, promote the deep combination of humic acid and nitrogen source, ensure the reaction proceeds fully, adapt to the kinetic requirements of the reaction process, shorten the overall reaction cycle, and protect the carboxyl and hydroxyl active groups of humic acid.

[0019] Preferably, in step S5, the stirring speed after adding the modified chitosan flocculant is 250~350 r / min and the stirring time is 4~6 min; The centrifuge speed is 2800~3200 r / min, and the centrifugation time is 12~18 min.

[0020] By adopting the above technical solution, the stirring operation after adding modified chitosan flocculant allows the flocculant to be uniformly dispersed in the material system. The specific groups in its molecular structure can fully contact the impurity particles in the system, realizing the directional adsorption and aggregation of impurities, forming easily separable flocs. Subsequently, the centrifuge generates centrifugal force through high-speed rotation, which efficiently separates the aggregated flocs from the filtrate containing humic acid-nitrogen complex. The filter residue is retained while the high-quality filtrate is collected, reducing the loss of effective components with the filter residue and ensuring the retention of effective components in the finished product.

[0021] Preferably, in step S6, the filter medium is a ceramic membrane with a pore size of 0.1~0.3μm, a filtration rate of 2~4L / min, and a filtration pressure of 0.1~0.2MPa. When adding the aminosilane coupling agent and stirring, the temperature should be 20~30℃, the stirring speed should be 180~220r / min, and the stirring time should be 6~10min.

[0022] By adopting the above technical solution, a ceramic membrane is used as the filter medium during filtration. Its specific pore size can trap trace suspended impurities remaining in the high-quality filtrate. The coordination of filtration speed and filtration pressure ensures that the filtration process proceeds in an orderly manner, further improving the purity of the filtrate. Subsequently, an aminosilane coupling agent is added, and stirring is performed to ensure that the coupling agent is evenly dispersed in the filtrate system. The functional groups in its molecules can interact with the residual metal ion catalyst and humic acid-nitrogen complex to form a stable binding structure, strengthening the structural integrity of the humic acid-nitrogen complex and providing a guarantee for avoiding precipitation, stratification, and reducing nitrogen loss during subsequent storage.

[0023] Preferably, in step S7, the cooling process involves introducing 5-10°C cooling water through the jacket of the cooling buffer tank to cool the material to 20-25°C, and the stirring speed during cooling is 100-150 r / min. The pressure during high-level buffer tank stabilization is 0.1~0.2MPa, and the stabilization time is 5~10min; The material conveying speed is 8~12L / min. Before filling, the material is filtered again by a terminal ceramic membrane filter with a pore size of 0.1~0.2μm. The filling is carried out by a fully automatic filling unit with a filling speed of 5~8L / min.

[0024] By adopting the above technical solution, during the cooling process, cooling water is introduced into the jacket of the cooling buffer tank, and the material temperature is uniformly reduced to the set range by stirring, which suppresses the structural fluctuation of the humic acid-nitrogen complex and enhances the stability of the system. The high-level buffer tank maintains constant pressure to balance the internal state of the material system and avoids structural imbalance caused by pressure changes during subsequent transportation. The material is transported at a stable speed, and before filling, it passes through a terminal ceramic membrane filter to remove trace impurities again, improving the purity of the finished product. The fully automatic filling unit completes the filling at the set speed to ensure uniform metering of the finished product. The entire process, combined with the cooling buffer and high-level pressure stabilization post-processing, further ensures that the product is free from precipitation and stratification when stored at room temperature, reducing nitrogen loss.

[0025] This invention provides a method for producing high-nitrogen humic acid liquid fertilizer. It has the following beneficial effects: 1. This invention improves the dispersibility of humic acid by using ionic liquid dispersant, combined with medium and low frequency ultrasonic mass transfer and segmented temperature-controlled catalytic process, so that humic acid can fully contact the reaction sites of nitrogen source and activator. At the same time, the dual-channel precise injection technology avoids local reaction imbalance and shortens the reaction cycle, making it more efficient than the traditional stepwise reaction process.

[0026] 2. The composite nitrogen source used in this invention has stronger binding stability with humic acid. The modified chitosan flocculant can directionally retain impurities, reduce the loss of effective components with filter residue, and the simultaneous acid-base complexation reaction protects the carboxyl and hydroxyl active groups of humic acid, thus significantly improving the yield of finished products.

[0027] 3. This invention enhances the structural stability of the humic acid-nitrogen complex through the synergistic effect of aminosilane coupling agent and residual metal ion catalyst. Combined with post-processing steps of cooling buffer and high-level voltage stabilization, the product exhibits no precipitation or stratification when stored at room temperature, has a low nitrogen loss rate, and provides more stable performance. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the method flow of the present invention. Detailed Implementation

[0029] The technical solution of the present invention will now be clearly and completely described 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.

[0030] Example 1 S1. Select raw materials, reaction promotion system and auxiliary components. The raw materials include lignite, composite nitrogen source, alkaline activator and acid regulator. The reaction promotion system includes ionic liquid dispersant and metal ion catalyst. The auxiliary components include modified chitosan flocculant, aminosilane coupling agent and deionized water. The raw materials consist of 10.0 parts by weight of lignite, 20.0 parts by weight of composite nitrogen source, 3.0 parts by weight of alkaline activator, and 2.0 parts by weight of acidic regulator. The reaction promotion system consists of 0.5 parts by weight of ionic liquid dispersant and 0.1 parts by weight of metal ion catalyst. The auxiliary components consist of 0.2 parts by weight of modified chitosan flocculant, 0.05 parts by weight of aminosilane coupling agent, and 45.0 parts by weight of deionized water. The composite nitrogen source is a mixture of urea and hydroxymethylurea in a weight ratio of 1:0.3. The alkaline activator is a mixture of potassium hydroxide and potassium carbonate in a weight ratio of 2:1. The ionic liquid dispersant is 1-butyl-3-methylimidazolium acetate, and the metal ion catalyst is anhydrous zinc chloride. The modified chitosan flocculant is chitosan modified with glycidyltrimethylammonium chloride, with a molecular weight of 100,000 Da. The aminosilane coupling agent is 3-aminopropyltriethoxysilane. S2. After the lignite is crushed and ground in sequence, it is mixed with deionized water and ionic liquid dispersant to form a humic acid suspension. The lignite was crushed to a particle size of 60 mesh by a jaw crusher and then ground to a particle size of 80 mesh by a planetary ball mill. The grinding speed was 300 r / min and the grinding time was 30 min. When it was mixed with deionized water and ionic liquid dispersant, the stirring speed was 500 r / min, the stirring temperature was 28℃, and the stirring time was 8 min. S3. Transfer the humic acid suspension into the reactor, and simultaneously inject the alkaline activator and acid regulator through the dual-pipe precision injection device. Turn on the ultrasonic-assisted mass transfer and maintain the reaction temperature through the steam in the outer pipe. During the ultrasonic-assisted reaction, the frequency was 20kHz, the power was 140W, the reaction temperature was 60℃, the reaction time was 8min, and the stirring speed of the reactor was 400r / min. S4. Add a composite nitrogen source and a metal ion catalyst to the system in step S3, and carry out the catalytic composite reaction in two stages. The temperature is maintained stable in both stages by steam in the outer tube. The process is divided into the following steps: In the first stage, the temperature is 58℃, the ultrasonic power is 140W, and the stirring speed is 400r / min, and the reaction is carried out for 4min; in the second stage, the temperature is raised to 63℃, and the ultrasonic power is 190W and the stirring speed is 500r / min, and the reaction is carried out for 10min. S5. Add modified chitosan flocculant to the material in step S4, stir, then transfer to a centrifuge for separation and collect the refined filtrate. The stirring speed after adding the modified chitosan flocculant was 250 r / min and the stirring time was 4 min; the centrifuge speed was 2800 r / min and the centrifugation time was 12 min. S6. After filtering the high-quality filtrate, add aminosilane coupling agent and stir to complete the secondary stabilization of the system; The filter medium used during filtration was a ceramic membrane with a pore size of 0.1 μm, a filtration rate of 2 L / min, and a filtration pressure of 0.1 MPa. When adding the aminosilane coupling agent and stirring, the temperature was 20 °C, the stirring speed was 180 r / min, and the stirring time was 6 min. S7. After cooling the material from step S6 to room temperature, it is pressure-stabilized in a high-level buffer tank and then transported to the filling port by a circulating pump to complete the filling. The cooling process involves introducing 5°C cooling water through the interlayer of the cooling buffer tank to cool the material to 20°C, with a stirring speed of 100 r / min during cooling. The pressure in the high-level buffer tank is 0.1 MPa, and the stabilization time is 5 min. The material conveying speed is 8 L / min. Before filling, the material is filtered again by a terminal ceramic membrane filter with a pore size of 0.1 μm. The filling process uses a fully automatic filling unit with a filling speed of 5 L / min.

[0031] Example 2 S1. Select raw materials, reaction promotion system and auxiliary components. The raw materials include lignite, composite nitrogen source, alkaline activator and acid regulator. The reaction promotion system includes ionic liquid dispersant and metal ion catalyst. The auxiliary components include modified chitosan flocculant, aminosilane coupling agent and deionized water. The raw materials consist of 12.5 parts lignite, 22.5 parts composite nitrogen source, 4.0 parts alkaline activator, and 3.0 parts acidic regulator by weight. The reaction promotion system consists of 0.75 parts ionic liquid dispersant and 0.2 parts metal ion catalyst by weight. The auxiliary components consist of 0.35 parts modified chitosan flocculant, 0.075 parts aminosilane coupling agent, and 50.0 parts deionized water by weight. The composite nitrogen source is a mixture of urea and hydroxymethylurea in a weight ratio of 1:0.3. The alkaline activator is a mixture of potassium hydroxide and potassium carbonate in a weight ratio of 2:1. The ionic liquid dispersant is 1-butyl-3-methylimidazolium acetate, and the metal ion catalyst is anhydrous zinc chloride. The modified chitosan flocculant is chitosan modified with glycidyltrimethylammonium chloride, with a molecular weight of 200,000 Da. The aminosilane coupling agent is 3-aminopropyltriethoxysilane. S2. After the lignite is crushed and ground in sequence, it is mixed with deionized water and ionic liquid dispersant to form a humic acid suspension. The lignite is crushed to a particle size of 70 mesh by a jaw crusher, and then ground to a particle size of 90 mesh by a planetary ball mill. The grinding speed is 350 r / min and the grinding time is 35 min. When it is mixed with deionized water and ionic liquid dispersant, the stirring speed is 550 r / min, the stirring temperature is 30℃, and the stirring time is 10 min. S3. Transfer the humic acid suspension into the reactor, and simultaneously inject the alkaline activator and acid regulator through the dual-pipe precision injection device. Turn on the ultrasonic-assisted mass transfer and maintain the reaction temperature through the steam in the outer pipe. During the ultrasonic-assisted reaction, the frequency was 21kHz, the power was 150W, the reaction temperature was 62.5℃, the reaction time was 10min, and the stirring speed of the reactor was 450r / min. S4. Add a composite nitrogen source and a metal ion catalyst to the system in step S3, and carry out the catalytic composite reaction in two stages. The temperature is maintained stable in both stages by steam in the outer tube. The process is divided into the following steps: In the first stage, the temperature is 60℃, the ultrasonic power is 150W, and the stirring speed is 450r / min, and the reaction is carried out for 5min; in the second stage, the temperature is raised to 65℃, and the ultrasonic power is 200W and the stirring speed is 550r / min, and the reaction is carried out for 12.5min. S5. Add modified chitosan flocculant to the material in step S4, stir, then transfer to a centrifuge for separation and collect the refined filtrate. The stirring speed after adding the modified chitosan flocculant was 300 r / min and the stirring time was 5 min; the centrifuge speed was 3000 r / min and the centrifugation time was 15 min. S6. After filtering the high-quality filtrate, add aminosilane coupling agent and stir to complete the secondary stabilization of the system; The filter medium used during filtration was a ceramic membrane with a pore size of 0.2 μm, a filtration rate of 3 L / min, and a filtration pressure of 0.15 MPa. When adding the aminosilane coupling agent and stirring, the temperature was 25℃, the stirring speed was 200 r / min, and the stirring time was 8 min. S7. After cooling the material from step S6 to room temperature, it is pressure-stabilized in a high-level buffer tank and then transported to the filling port by a circulating pump to complete the filling. The cooling process involves introducing 7.5℃ cooling water through the interlayer of the cooling buffer tank to cool the material to 22.5℃, with a stirring speed of 125 r / min during cooling. The pressure in the high-level buffer tank is 0.15 MPa, and the stabilization time is 7.5 min. The material conveying speed is 10 L / min. Before filling, the material is filtered again by a terminal ceramic membrane filter with a pore size of 0.15 μm. The filling process uses a fully automatic filling unit with a filling speed of 6.5 L / min.

[0032] Example 3 S1. Select raw materials, reaction promotion system and auxiliary components. The raw materials include lignite, composite nitrogen source, alkaline activator and acid regulator. The reaction promotion system includes ionic liquid dispersant and metal ion catalyst. The auxiliary components include modified chitosan flocculant, aminosilane coupling agent and deionized water. The raw materials consist of 15.0 parts by weight of lignite, 25.0 parts by weight of composite nitrogen source, 5.0 parts by weight of alkaline activator, and 4.0 parts by weight of acidic regulator. The reaction promotion system consists of 1.0 part by weight of ionic liquid dispersant and 0.3 parts by weight of metal ion catalyst. The auxiliary components consist of 0.5 parts by weight of modified chitosan flocculant, 0.1 parts by weight of aminosilane coupling agent, and 55.0 parts by weight of deionized water. The composite nitrogen source is a mixture of urea and hydroxymethylurea in a weight ratio of 1:0.3. The alkaline activator is a mixture of potassium hydroxide and potassium carbonate in a weight ratio of 2:1. The ionic liquid dispersant is 1-butyl-3-methylimidazolium acetate, and the metal ion catalyst is anhydrous zinc chloride. The modified chitosan flocculant is chitosan modified with glycidyltrimethylammonium chloride, with a molecular weight of 300,000 Da. The aminosilane coupling agent is 3-aminopropyltriethoxysilane. S2. After the lignite is crushed and ground in sequence, it is mixed with deionized water and ionic liquid dispersant to form a humic acid suspension. The lignite was crushed to a particle size of 80 mesh by a jaw crusher, and then ground to a particle size of 100 mesh by a planetary ball mill. The grinding speed was 400 r / min and the grinding time was 40 min. When it was mixed with deionized water and ionic liquid dispersant, the stirring speed was 600 r / min, the stirring temperature was 32℃, and the stirring time was 12 min. S3. Transfer the humic acid suspension into the reactor, and simultaneously inject the alkaline activator and acid regulator through the dual-pipe precision injection device. Turn on the ultrasonic-assisted mass transfer and maintain the reaction temperature through the steam in the outer pipe. During the ultrasonic-assisted reaction, the frequency was 22kHz, the power was 160W, the reaction temperature was 65℃, the reaction time was 12min, and the stirring speed of the reactor was 500r / min. S4. Add a composite nitrogen source and a metal ion catalyst to the system in step S3, and carry out the catalytic composite reaction in two stages. The temperature is maintained stable in both stages by steam in the outer tube. The process is divided into the following steps: In the first stage, the temperature is 62℃, the ultrasonic power is 160W, and the stirring speed is 500r / min, and the reaction is carried out for 6min; in the second stage, the temperature is raised to 67℃, and the ultrasonic power is 210W and the stirring speed is 600r / min, and the reaction is carried out for 15min. S5. Add modified chitosan flocculant to the material in step S4, stir, then transfer to a centrifuge for separation and collect the refined filtrate. The stirring speed after adding the modified chitosan flocculant was 350 r / min and the stirring time was 6 min; the centrifuge speed was 3200 r / min and the centrifugation time was 18 min. S6. After filtering the high-quality filtrate, add aminosilane coupling agent and stir to complete the secondary stabilization of the system; The filter medium used during filtration was a ceramic membrane with a pore size of 0.3 μm, a filtration rate of 4 L / min, and a filtration pressure of 0.2 MPa. When adding the aminosilane coupling agent and stirring, the temperature was 30℃, the stirring speed was 220 r / min, and the stirring time was 10 min. S7. After cooling the material from step S6 to room temperature, it is pressure-stabilized in a high-level buffer tank and then transported to the filling port by a circulating pump to complete the filling. The cooling process involves introducing 10°C cooling water through the jacket of the cooling buffer tank to cool the material to 25°C, with a stirring speed of 150 r / min during cooling. The pressure in the high-level buffer tank is 0.2 MPa, and the stabilization time is 10 min. The material conveying speed is 12 L / min. Before filling, the material is filtered again through a terminal ceramic membrane filter with a pore size of 0.2 μm. The filling process uses a fully automatic filling unit with a filling speed of 8 L / min.

[0033] Comparative Example 1 The only difference from Example 1 is that the complex nitrogen source is replaced with a single urea, and hydroxymethylurea is not added.

[0034] Comparative Example 2 The only difference from Example 1 is that 1-butyl-3-methylimidazolium acetate was not added, and the weight of deionized water was adjusted to make up the total weight.

[0035] Comparative Example 3 The only difference from Example 1 is that the modified chitosan flocculant is replaced with unmodified ordinary chitosan.

[0036] Comparative Example 4 The only difference from Example 1 is that ultrasound-assisted mass transfer was not activated in steps S3 and S4.

[0037] Comparative Example 5 The only difference from Example 1 is that the dual-channel precision injection device was not used in step S3. Instead, the alkaline activator was injected first and reacted for 5 minutes before the acidic regulator was injected.

[0038] Comparative Example 6 The only difference from Example 1 is that anhydrous zinc chloride was not added.

[0039] Comparative Example 7 The only difference from Example 1 is that a staged catalytic composite reaction was not used in step S4. Instead, the temperature was maintained at 60°C, the ultrasonic power was 140W, the stirring speed was 400r / min, and the reaction was continued for 14min.

[0040] Comparative Example 8 The only difference from Example 1 is that the alkaline activator is replaced with a single industrial-grade potassium hydroxide.

[0041] Experiment 1: Reaction Period Detection The timing started when the alkaline activator and acidic regulator were simultaneously injected in step S3, and ended when the catalytic composite reaction was completely completed in step S4. The total reaction period for each sample was recorded. Experimental results were recorded in minutes; a shorter reaction period indicated higher reaction efficiency.

[0042] Experiment 2: Finished Product Yield Testing Each raw material was accurately weighed according to the schemes of Examples 1-3 and Comparative Examples 1-8, and converted to actual mass according to weight parts, accurate to 0.01g. The total mass of raw materials for each sample, Mtotal, was accumulated. Then, the preparation was completed according to the corresponding steps, ensuring no material leakage or loss during filtration, centrifugation, and filling. The actual mass of the final filled product, Myield, was accurately weighed. The yield of each sample was calculated using the formula: Yield (%) = (Myield / Mtotal) × 100%. All weighing operations used the same electronic balance with an accuracy of 0.01g to reduce systematic errors. A higher yield indicates less loss of active ingredients.

[0043] Experiment 3: Product Stability Testing The finished products of Examples 1-3 and Comparative Examples 1-8 were respectively placed into 500mL sealed glass containers, with three parallel samples per group. They were stored at room temperature for three months, avoiding direct sunlight and vigorous shaking during storage. At the initial storage time T0, the total nitrogen content N0 of each sample was determined using GB / T8572-2010 "Determination of Total Nitrogen Content in Compound Fertilizers - Distillation Titration Method" (Kjeldahl method). After three months of storage (T3), the total nitrogen content N3 of each sample was determined again using the same method. The nitrogen loss rate (%) was calculated using the formula: Nitrogen Loss Rate (%) = (N0 - N3) / N0 × 100%. Simultaneously, the appearance of each sample at T3 was observed, recording any precipitation, stratification, discoloration, or other phenomena. The average value was taken as the final data. A lower nitrogen loss rate and the absence of precipitation or stratification indicate better product stability.

[0044] Table 1 Reaction cycle detection data

[0045] Table 2 Finished Product Yield Test Data

[0046] Table 3

[0047] By comparing the experimental data of the examples and the comparative examples, it can be seen that: Combining Example 1 and Comparative Examples 2, 4, 5, and 7 with Table 1, it can be seen that the improved reaction efficiency of high-nitrogen humic acid liquid fertilizer relies on the synergistic effect of ionic liquid dispersant, ultrasound-assisted mass transfer, segmented temperature-controlled catalysis, and dual-channel precise injection technology. The reaction cycles of Comparative Examples 2, 4, 5, and 7 reached 31.5 min, 35.8 min, 28.6 min, and 29.4 min, respectively, all significantly longer than the 22.0 min of Example 1. Comparative Example 4, in particular, had the longest reaction cycle due to insufficient contact at the reaction sites caused by the lack of ultrasound-assisted mass transfer. This indicates that ionic liquid improves the dispersibility of humic acid, ultrasound enhances mass transfer, segmented temperature control matches reaction kinetics, and dual-channel injection avoids local imbalance; the synergistic effect of these four factors shortens the reaction cycle, and the absence or replacement of any single technological feature cannot achieve the same efficiency.

[0048] Combining Example 2 and Comparative Examples 1, 3, and 5 with Table 2, it can be seen that the key to improving the finished product yield lies in the synergistic effect of the composite nitrogen source, the modified chitosan flocculant, and the simultaneous acid-base complexation reaction. The finished product yields of Comparative Examples 1, 3, and 5 were 85.41%, 83.17%, and 84.95%, respectively, all lower than the 92.38% of Example 2. Among them, Comparative Example 3 had the lowest yield because ordinary chitosan had poor flocculation selectivity, resulting in a greater loss of effective components along with impurities. This indicates that the composite nitrogen source has a more stable combination with humic acid, the modified chitosan directionally retains impurities, and the simultaneous acid-base complexation protects the active groups of humic acid. The three work synergistically to reduce the loss of effective components, and replacing the core components or adjusting the process will lead to a significant decrease in yield.

[0049] Combining Example 3 and Comparative Examples 1, 3, and 6 with Table 3, it can be seen that the excellent storage stability of the product is the result of the combined effect of the aminosilane coupling agent, the metal ion catalyst, and the cooling and stabilization post-treatment. The nitrogen loss rates of Comparative Examples 1, 3, and 6 reached 3.76%, 2.35%, and 4.32%, respectively. Comparative Example 3 showed a small amount of precipitation, while Comparative Example 6 had the highest nitrogen loss rate, far less than the 2.01% of Example 3, and no precipitation stratification. This indicates that the aminosilane coupling agent forms stable coordination bonds with the residual metal ion catalyst, the cooling and stabilization optimizes the system state, and the structural stability of the composite nitrogen source, together with the other three, synergistically reduce nitrogen loss and avoid precipitation stratification. The absence of any one of these key components will lead to a decrease in stability.

[0050] Combining Example 1 and Comparative Examples 6, 2, and 3 with Tables 1-3, it can be seen that the high efficiency, high yield, and stable performance of this invention are the result of a chain reaction of synergistic effects across the entire technical system. Comparative Example 6, with its anhydrous zinc chloride, not only had the highest nitrogen loss rate of 4.32%, but its yield of 88.76% was also lower than that of Example 1 (89.65%). Comparative Example 2 had a reaction cycle of 31.5 min, which was too long, and Comparative Example 3 had the lowest yield and exhibited precipitation. In contrast, Example 1, through the synergistic effect of its core features such as ionic liquid, ultrasound, segmented catalysis, composite nitrogen source, and modified chitosan, achieved a balanced and excellent performance with a reaction cycle of 22.0 min, a yield of 89.65%, and a nitrogen loss rate of 2.13%.

[0051] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for producing a high-nitrogen humic acid liquid fertilizer, characterized in that, Includes the following steps: S1. Select raw materials, reaction promotion system and auxiliary components. The raw materials include lignite, composite nitrogen source, alkaline activator and acid regulator. The reaction promotion system includes ionic liquid dispersant and metal ion catalyst. The auxiliary components include modified chitosan flocculant, aminosilane coupling agent and deionized water. S2. After the lignite is crushed and ground in sequence, it is mixed with deionized water and ionic liquid dispersant to form a humic acid suspension. S3. Transfer the humic acid suspension into the reactor, and simultaneously inject the alkaline activator and acid regulator through the dual-pipe precision injection device. Turn on the ultrasonic-assisted mass transfer and maintain the reaction temperature through the steam in the outer pipe. S4. Add a composite nitrogen source and a metal ion catalyst to the system in step S3, and carry out the catalytic composite reaction in two stages. The temperature is maintained stable in both stages by steam in the outer tube. S5. Add modified chitosan flocculant to the material in step S4, stir, then transfer to a centrifuge for separation and collect the refined filtrate. S6. After filtering the high-quality filtrate, add aminosilane coupling agent and stir to complete the secondary stabilization of the system; S7. After cooling the material from step S6 to room temperature, it is pressure-stabilized in a high-level buffer tank and then transported to the filling port by a circulating pump to complete the filling.

2. The method for producing a high-nitrogen humic acid liquid fertilizer according to claim 1, characterized in that, In step S1, the raw materials consist of 10.0-15.0 parts by weight of lignite, 20.0-25.0 parts by weight of composite nitrogen source, 3.0-5.0 parts by weight of alkaline activator, and 2.0-4.0 parts by weight of acidic regulator. The reaction promotion system consists of 0.5-1.0 parts by weight of ionic liquid dispersant and 0.1-0.3 parts by weight of metal ion catalyst. The auxiliary components consist of 0.2-0.5 parts by weight of modified chitosan flocculant, 0.05-0.1 parts by weight of aminosilane coupling agent, and 45.0-55.0 parts by weight of deionized water.

3. The method for producing a high-nitrogen humic acid liquid fertilizer according to claim 2, characterized in that, The composite nitrogen source is composed of urea and hydroxymethylurea in a weight ratio of 1:0.3, the alkaline activator is composed of potassium hydroxide and potassium carbonate in a weight ratio of 2:1, the ionic liquid dispersant is 1-butyl-3-methylimidazolium acetate, and the metal ion catalyst is anhydrous zinc chloride.

4. The method for producing a high-nitrogen humic acid liquid fertilizer according to claim 2, characterized in that, The modified chitosan flocculant is chitosan modified with glycidyltrimethylammonium chloride, with a molecular weight of 100,000~300,000 Da, and the aminosilane coupling agent is 3-aminopropyltriethoxysilane.

5. The method for producing a high-nitrogen humic acid liquid fertilizer according to claim 1, characterized in that, In step S2, lignite is crushed to a particle size of 60-80 mesh by a jaw crusher, and then ground to a particle size of 80-100 mesh by a planetary ball mill. The grinding speed is 300-400 r / min and the grinding time is 30-40 min. When mixing with deionized water and ionic liquid dispersant, the stirring speed is 500~600 r / min, the stirring temperature is 28~32℃, and the stirring time is 8~12 min.

6. The method for producing a high-nitrogen humic acid liquid fertilizer according to claim 1, characterized in that, In step S3, when using ultrasonic assistance, the frequency is 20kHz~22kHz, the power is 140~160W, the reaction temperature is 60~65℃, the reaction time is 8~12min, and the stirring speed of the reactor is 400~500r / min.

7. The method for producing a high-nitrogen humic acid liquid fertilizer according to claim 1, characterized in that, The S4 step consists of two stages as follows: The first stage is carried out at a temperature of 58~62℃, an ultrasonic power of 140~160W, a stirring speed of 400~500r / min, and a reaction time of 4~6min. In the second stage, the temperature is raised to 63~67℃, and the reaction is continued for 10~15 minutes with an ultrasonic power of 190~210W and a stirring speed of 500~600r / min.

8. The method for producing a high-nitrogen humic acid liquid fertilizer according to claim 1, characterized in that, In step S5, the stirring speed after adding the modified chitosan flocculant is 250~350 r / min and the stirring time is 4~6 min; The centrifuge speed is 2800~3200 r / min, and the centrifugation time is 12~18 min.

9. The method for producing a high-nitrogen humic acid liquid fertilizer according to claim 1, characterized in that, In step S6, the filter medium is a ceramic membrane with a pore size of 0.1~0.3μm, a filtration rate of 2~4L / min, and a filtration pressure of 0.1~0.2MPa. When adding the aminosilane coupling agent and stirring, the temperature should be 20~30℃, the stirring speed should be 180~220r / min, and the stirring time should be 6~10min.

10. The method for producing a high-nitrogen humic acid liquid fertilizer according to claim 1, characterized in that, In step S7, cooling water at 5-10°C is introduced through the jacket of the cooling buffer tank to cool the material to 20-25°C. The stirring speed during cooling is 100-150 r / min. The pressure during high-level buffer tank stabilization is 0.1~0.2MPa, and the stabilization time is 5~10min; The material conveying speed is 8~12L / min. Before filling, the material is filtered again by a terminal ceramic membrane filter with a pore size of 0.1~0.2μm. The filling is carried out by a fully automatic filling unit with a filling speed of 5~8L / min.

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