Production process of slow-release compound fertilizer

Abstract

The invention discloses a production process of a slow-release compound fertilizer, which comprises the following steps: preparing various simple substance raw materials; granulating the elementary substance raw material to obtain elementary substance raw material particles; coating the elementary substance raw material particles with a sustained-release film according to design requirements to obtain sustained-release raw material particles; mixing and drying the slow-release raw material particles according to design requirements; and packaging to obtain the finished slow-release compound fertilizer. Each elementary substance raw material is coated with the slow-release films with different release periods according to the requirements of crop growth periods on nutrients, so that fertilization of corresponding nutrients required by different growth periods of crops can be accurately realized, the phenomenon of waste of redundant nutrients is effectively prevented, nutrient supply in different stages is provided by stage slow release, and the yield of crops is improved. The precise fertilization of one-season crops only by applying the fertilizer once is really realized.

Description

Technical Field

[0001] The present invention relates to the field of compound fertilizers, in particular to a production process of a slow-release compound fertilizer. Background Art

[0002] Slow-release compound fertilizer is a fertilizer with a special release mechanism. It uses technical means to slow down the release rate of nutrients to meet the needs of crops at different growth stages.

[0003] After searching, the Chinese patent with publication number CN119775072A discloses an environmentally friendly slow-release compound fertilizer. Its preparation method includes four steps: initial coating, uniform mixing, secondary coating granulation and fluidized bed reaction film formation. The slow-release agent is composed of castor oil, polyoxypropylene triol, polymerized MDI and modified silica, and the modified silica is obtained through specific chemical treatment.

[0004] Although it can form a slow-release film on the surface of the fertilizer to extend the release period, due to the different requirements of crops for different fertilizer nutrients in different production periods, the use of such mixed fertilizers for fertilization is prone to nutrient waste, making it difficult to achieve precise fertilization, and needs further improvement. Summary of the Invention

[0005] In order to further reduce nutrient waste and achieve precise fertilization, the present application provides a production process for a slow-release compound fertilizer.

[0006] The present application provides a production process for a slow-release compound fertilizer, which adopts the following technical solution: A production process for a slow-release compound fertilizer comprises the following steps: S1, preparation of various elemental raw materials; S2, granulating the elemental raw material to obtain elemental raw material particles; S3, coating the single-substance raw material particles with a sustained-release film according to design requirements to obtain sustained-release raw material particles; S4, mixing and drying the sustained-release raw material particles according to design requirements; S5, packaging to obtain the finished slow-release compound fertilizer.

[0007] Optionally, the elemental raw material particles obtained in step S2 are screened, and the elemental raw material particles that meet the particle size are transported to a silo for storage, and the elemental raw material particles that do not meet the particle size are used as raw materials again for granulation.

[0008] Optionally, in step S3, the sustained-release membrane coated with the same elemental raw material particles has different release cycles.

[0009] Optionally, the diameter of the single-substance raw material particles is 3.3-4.7 mm and they are spherical.

[0010] Optionally, the sustained-release membrane in step S3 includes an initial sustained-release membrane, the material of which includes 5%-15% hydroxypropyl cellulose, 90%-80% ethanol, 2%-3% dispersant, 1%-2% plasticizer, and 0.5%-1% stabilizer, which are dissolved item by item in a reactor to form a film-forming solution.

[0011] Optionally, the sustained-release membrane in step S3 includes a medium-term sustained-release membrane, and the materials of the medium-term sustained-release membrane include 5%-35% tung oil, 1%-5% turpentine, 30%-50% ethyl acetate, 20%-30% fatty acid triglyceride, 1%-2% defoaming agent, 1%-2% stabilizer, and 2%-3% film-forming aid, which are dissolved one by one in a reactor to form a film-forming solution.

[0012] Optionally, the sustained-release membrane in step S3 includes a late sustained-release membrane, and the material of the late sustained-release membrane includes 20%-40% sulfur, 5%-10% hydroxypropyl cellulose, 60%-80% carbon disulfide, 1%-2% defoaming agent, 1%-2% stabilizer, and 2%-3% film-forming aid, which are dissolved one by one in a reactor to form a film-forming solution.

[0013] Optionally, the film-forming solution is evenly sprayed onto the curtain of fertilizer particles lifted by the lifting plate in the drum through an atomizing device at an air pressure of 0.1-0.5 MPA, forming a complete slow-release film on the surface of the fertilizer particles.

[0014] Optionally, the raw material particles are transported between each process using a gas conveying device, the gas conveying device includes a conveying pipe, an axially arranged partition is provided in the conveying pipe, the upper part of the partition is the raw material particle conveying area, the lower part of the partition is the gas conveying area, the two ends of the conveying pipe are respectively provided with an air inlet and an air outlet, the air inlet and the air outlet are both connected to the gas conveying area, the top two ends of the conveying pipe are respectively provided with a feed port and a discharge port, the air inlet is connected to a high-pressure gas source.

[0015] Optionally, a gas guide is provided in the gas delivery area of ​​the delivery pipe, and the gas guide includes guide plates hinged to each other, and the guide plates are all inclined.

[0016] In summary, this application includes at least one of the following beneficial technical effects: 1. The single raw materials are first granulated to achieve uniform size and density, thereby improving the uniformity of nutrients in the final mixed compound fertilizer; 2. Each single raw material is coated with a slow-release film with different release cycles according to the nutrient requirements of the crop growth cycle, so that the corresponding nutrients required for different growth cycles of crops can be accurately applied, and the waste of excess nutrients can be effectively prevented. In this way, the phased slow release provides nutrient supply at different stages, truly realizing precise fertilization with only one fertilization per season. 3. The raw material particles are transported in each process using a closed gas conveying device, which overcomes the phenomenon of material overflow, dust splashing or moisture absorption and adhesion caused by traditional transportation, and effectively improves the production environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a flow chart of an embodiment of the present application.

[0018] Figure 2 It is a structural diagram of the gas delivery device in an embodiment of the present application.

[0019] Figure 3 yes Figure 2 Enlarged view of point A in the middle.

[0020] Description of reference numerals: 1. Conveying pipe; 2. Partition; 3. Raw material particle conveying area; 4. Gas conveying area; 5. Air inlet; 6. Air outlet; 7. Feed port; 8. Discharge port; 9. Gas guide; 10. Guide plate; 11. Wave crest; 12. Wave trough; 13. Support block; 14. Movable end; 15. Locking screw; 16. Connecting part; 17. Magnet block; 18. Operating end; 19. Return spring; 20. Cover plate. DETAILED DESCRIPTION

[0021] The following is combined with Figure 1-3 This application is described in further detail.

[0022] A production process for slow-release compound fertilizer, such as Figure 1 As shown, it mainly includes the following steps: S1, preparation of various elemental raw materials; After purchasing all the raw materials needed to produce compound fertilizer, unpack them and distribute them.

[0023] S2, granulating various elemental raw materials to obtain elemental raw material particles; Various elemental raw materials are conveyed to a granulator through a feeding system, and the granulator granulates the various elemental raw materials to obtain elemental raw material particles. In this embodiment, the diameter of the elemental raw material particles is 3.3-4.7 mm and they are spherical.

[0024] S3, screening and storing the single-element raw material particles; The elemental raw materials obtained by granulation are screened by a screening machine, and the elemental raw material particles that meet the particle size are transported to the silo for storage, and the elemental raw materials that do not meet the particle size are re-transported to the granulator in step S2 for re-granulation, so as to realize the recycling of the elemental particles and reduce waste; a spiral downward slide is provided in the silo, and the elemental raw material particles enter through the top of the silo, and then slide along the slide to the bottom of the silo for storage, so as to prevent the elemental particles from falling directly and breaking. In addition, a dehumidifier with automatic exhaust is provided in the silo, which can control the internal humidity, achieve good moisture-proof effect, and ensure that the elemental raw materials are well stored in the silo; a discharge port is provided at the bottom of the silo and an electronic belt scale is provided at the discharge port to realize quantitative discharge.

[0025] S4, coating the single-substance raw material particles with a sustained-release film according to design requirements to obtain sustained-release raw material particles; According to the different needs of crops for various nutrients in different growth cycles, coating equipment is used to coat each elemental raw material particle with a slow-release film for the required period to obtain slow-release raw material particles; the same elemental raw material can be coated with a slow-release film of the same slow-release period or with slow-release films of different slow-release periods; different elemental raw materials can be coated with a slow-release film of the same slow-release period or with slow-release films of different slow-release periods.

[0026] S5, mixing and drying the slow-release raw material particles according to design requirements; According to the nutrient requirements of crop growth and harvest, slow-release raw material particles with corresponding slow-release cycles are selected and fully mixed through a mixer. After mixing, they are dried through a dryer to obtain compound fertilizers with the required nutrients.

[0027] S6, packaging to obtain the finished slow-release compound fertilizer; The mixed compound fertilizer is packaged by a packaging machine to obtain a finished slow-release compound fertilizer.

[0028] Each single raw material is coated with a slow-release film with different release cycles according to the nutrient requirements of the crop growth cycle, so that the corresponding nutrients required for different growth cycles of crops can be accurately applied, and the waste of excess nutrients can be effectively prevented. This phased slow release provides nutrient supply at different stages, truly realizing precise fertilization of crops only once a season.

[0029] Taking early rice crops as an example, special fertilizer for early rice is prepared according to the above process.

[0030] This fertilizer is specifically formulated for early rice, with a nutrient ratio of nitrogen:phosphorus:potassium = 16:7:8. The planned release cycle is: initial nitrogen release rate ≤ 10% (7 days), mid-term nitrogen release rate ≤ 50% (28 days), mid-term phosphorus release rate ≤ 75%, mid-term potassium release rate ≤ 75%, and cumulative nitrogen release rate ≥ 80% (60 days). The phosphorus release rate is ≥ 80% during the release period. The potassium release rate is ≥ 80% during the release period. In accordance with the release requirements of the slow-release fertilizer industry standard HG / T3931-2007, the fertilizer components (nutrients), slow-release cycle, and coating material are designed as follows: Nutrient ratio---N:P:K=16:7:8, compound fertilizer preparation: ammonium chloride 69%, monoammonium phosphate 17%, potassium chloride 14%; that is, the elemental raw materials are ammonium chloride, monoammonium phosphate and potassium chloride.

[0031] The above-mentioned single-substance raw materials were weighed respectively and granulated by double-roll extrusion to obtain corresponding single-substance raw material particles with a particle diameter of 4 mm.

[0032] The above-mentioned single-element raw material particles are coated with slow-release films with different slow-release cycles and different nutrient combinations through a rotary drum coating agent. Specific examples are as follows: 1. Preparation of nitrogen, phosphorus and potassium controlled-release fertilizer with 7-day quantitative release: 1) The initial nutrient release period is 7 days, of which the nitrogen release is ≤15% (total nitrogen content); the phosphorus release is 0%; and the potassium release is 0%.

[0033] 2) Process: Preparation of 7-day release coating material: Weigh 5%-15% hydroxypropyl cellulose, 90%-80% ethanol, 2%-3% dispersant, 1%-2% plasticizer, and 0.5%-1% stabilizer, and dissolve them one by one in a reaction kettle to form a clear, uniform, and stable film-forming solution.

[0034] 3) Granular fertilizer with a total amount of 15% ammonium chloride is loaded into a rotary drum and sprayed through an atomizing spray device. The above-mentioned film-forming solution is evenly sprayed onto the curtain of fertilizer particles raised by the scraper in the rotary drum at an air pressure of 0.1-0.5 MPA, so that the surface of the fertilizer particles is evenly coated with a layer of film-forming agent liquid. As the material flows, the solvent portion in the solution gradually evaporates, and the remaining film-forming substance forms a complete coating on the surface of the fertilizer particles, sealing the fertilizer particles.

[0035] 4) obtaining nitrogen, phosphorus and potassium controlled-release fertilizer particles coated with a slow-release membrane with an initial release period of 7 days.

[0036] 2. Production of nitrogen, phosphorus and potassium controlled-release fertilizer with 28-day quantitative release: 1) Weigh 5%-35% tung oil, 1%-5% turpentine, 30%-50% ethyl acetate, 20%-30% fatty acid triglyceride, 1%-2% defoamer, 1%-2% stabilizer, and 2%-3% film-forming aid. Add these ingredients one by one into a reaction kettle and dissolve them into a light yellow, uniform, stable, diluted tung oil solution.

[0037] 2) Weigh 50% of the ammonium chloride granules, 75% of the total amount of monoammonium phosphate granules, and 75% of the total amount of potassium chloride granules, and place them into separate coating cylinders.

[0038] 3) The coating solution is evenly sprayed onto the curtain of fertilizer particles lifted by the scraper in the drum at an air pressure of 0.1-0.5 MPA through an atomizing spray device, so that the surface of the fertilizer particles is evenly coated with a layer of film-forming aid liquid. As the material flows, the solvent part of the solution gradually evaporates, and the remaining film-forming substance forms a complete coating on the surface of the fertilizer particles, enclosing the fertilizer particles.

[0039] 4) The coated particles are homogenized and mixed in a mixing drum and stored for later use, thereby producing a nitrogen, phosphorus and potassium controlled-release fertilizer that releases quantitatively for 28 days.

[0040] 3. Preparation of 60-day quantitative release nitrogen, phosphorus and potassium controlled-release fertilizer: 1) preparing a film-forming solution comprising 20%-40% sulfur, 5%-10% hydroxypropyl cellulose, 60%-80% carbon disulfide, 1%-2% defoaming agent, 1%-2% stabilizer, and 2%-3% film-forming aid.

[0041] 2) Weigh out the remaining 20% ​​of the ammonium chloride granules, 25% of the total amount of the monoammonium phosphate granules, and 25% of the total amount of the potassium chloride granules, and place them into separate coating cylinders.

[0042] 3) The coating solution is evenly sprayed onto the curtain of fertilizer particles lifted by the scraper in the drum at an air pressure of 0.1-0.5 MPA through an atomizing spray device, so that the surface of the fertilizer particles is evenly coated with a layer of film-forming aid liquid. As the material flows, the solvent part of the solution gradually evaporates, and the remaining film-forming substance forms a complete coating on the surface of the fertilizer particles, enclosing the fertilizer particles.

[0043] 4) The coated particles are homogenized and mixed in a mixing drum and stored for use, thereby producing a nitrogen, phosphorus and potassium controlled-release fertilizer that releases a fixed amount of nitrogen, phosphorus and potassium for 60 days.

[0044] The remaining ammonium chloride granules are coated with a sustained-release film for a period of more than 60 days.

[0045] Finally, the various nitrogen, phosphorus and potassium controlled-release fertilizers with different release cycles mentioned above (controlled-release fertilizers with other release cycles can also be made according to design requirements) are mixed, homogenized and packaged to ultimately form special controlled-release fertilizers with different release amounts and different release cycles.

[0046] During production, controlled-release fertilizers are applied through specialized fertilizer spreading machines, either through "hole-drilling" or through specialized fertilization programs based on design requirements. Field trials of controlled-release fertilizers have shown that controlled-release fertilizers, through their controlled release of nutrients, provide crops with accurate, appropriate, and timely fertilizer delivery throughout their growth cycle, resulting in a 10%-15% increase in grain yield compared to other fertilizers. With the gradual realization of precision fertilization goals, my country's grain production will be further strengthened.

[0047] like Figure 2 As shown, in the actual production process, each process involves the transportation of raw material particles. In this embodiment, a gas conveying device is used for transportation. The gas conveying device includes a conveying pipe 1. A partition screen 2 is arranged in the axial direction inside the conveying pipe 1. The aperture of the partition screen 2 is smaller than the diameter of the raw material particles. The partition screen 2 divides the interior of the conveying pipe 1 into two layers, an upper layer and an lower layer, wherein the upper layer of the partition screen 2 is a raw material particle conveying area 3 for conveying raw material particles, and the lower layer of the partition screen 2 is a gas conveying area 4. In addition, an air inlet 5 and an air outlet 6 are provided at both ends of the conveying pipe 1, which are respectively connected to the gas conveying area 4; in actual use, the conveying pipe 1 is tilted, and the air inlet 5 is arranged at the upper end of the conveying pipe 1. At the high end, the air outlet 6 is set at the low end of the conveying pipe 1, and the air inlet 5 is used to connect with the high-pressure air source through a pipeline. At the high end of the conveying pipe 1, there is a feed port 7 connected to the raw material particle conveying area 3, and at the low end of the conveying pipe 1, there is a discharge port 8 connected to the raw material particle conveying area 3. During the conveying process, the raw material particles enter from the feed port 7, and then continue to fall along the partition 2 under the action of their own gravity and are finally discharged through the discharge port 8. During this period, the high-pressure air source is introduced from the air inlet 5 and finally discharged from the air outlet 6. The gas flow of the high-pressure air source is used to further promote the transportation of the raw material particles, ensuring that the raw material particles can be transported well and stably in the conveying pipe 1. In this embodiment, the conveying pipe 1 adopts a high-pressure polyethylene pipe, which is the conveying body, and the compressed air at the bottom is removed to promote the flow of granular material; in actual use, the inclined conveying pipe 1 can be combined with a material hoist for alternating connection. The material hoist lifts the granular raw material at the lower position to the feed port 7 at the upper position of the conveying pipe 1, and the material at the lower discharge port 8 of the conveying pipe 1 enters the material hoist. Such alternating cycle can realize the continuous conveying of granular raw materials.

[0048] The raw material particles are transported in each process using a closed gas conveying device, which overcomes the phenomenon of material overflow, dust splashing or moisture absorption and adhesion caused by traditional conveying, and effectively improves the production environment.

[0049] like Figure 2 As shown, a gas guide 9 is provided in the gas delivery area 4 of the delivery pipe 1, and the gas guide 9 includes a plurality of guide plates 10 hinged to each other, and each guide plate 10 is tilted. The gas guide 9 is wavy and fluctuates up and down, and forms a crest 11 and a trough 12 at each connection. The bottom end of the guide plate 10 is slidably connected to the delivery pipe 1, and a support block 13 for supporting the end of the gas guide 9 is provided at a low end of the gas delivery area 4 of the delivery pipe 1. The end of the gas guide 9 away from the support block 13 is a movable end 14, and the delivery pipe 1 is provided with a locking member for locking the movable end 14 of the gas guide 9.

[0050] With the help of the setting of the gas guide 9, the high-pressure gas source introduced into the air inlet 5 can flow upward at an angle under the guidance of the slope formed by the gas guide 9, so that the raw material particles can be better conveyed through the partition 2, and by changing the flow direction of the gas to a certain extent, it can also play a certain role in clearing the partition 2, thereby reducing the blockage of the partition 2; the gas guide 9 is composed of guide plates 10 that are hinged to each other to form a whole, which is convenient for overall disassembly and assembly. In addition, the sliding connection of the gas guide 9 can be used to push the guide plate 10 to make it flip around the hinge point at different angles in actual use, thereby realizing the adjustment of the slope angle of the gas guide 9. In actual use, the slope and height of the gas guide 9 can be adjusted according to actual needs to achieve better use effect and improve applicability.

[0051] like Figure 2 and Figure 3 As shown, the locking member includes a locking screw 15, and a connecting portion 16 is hinged at the movable end 14 of the gas guide 9, and the connecting portion 16 is slidably connected to the conveying pipe 1, and the end of the locking screw 15 is magnetically connected to the connecting portion 16 in a detachable manner, that is, corresponding magnet blocks 17 are provided on the end of the locking screw 15 and the connecting portion 16 to achieve adsorption and fixation, and the other end of the locking screw 15 passes through the conveying pipe 1 to form an operating end 18, and the locking screw 15 is threadedly connected to the end of the conveying pipe 1, so that the position of the connecting portion 16 is adjusted by rotating the locking screw 15, thereby driving the guide plate 10 to fold at different angles at the hinge to achieve adjustment of the state of the gas guide 9, which is simple and convenient. In other embodiments, the locking member can also be driven by a cylinder.

[0052] In addition, a reset spring 19 connecting the connecting portion 16 and the inner wall of the end of the conveying pipe 1 is provided. One end of the reset spring 19 is fixed on the connecting portion 16, and the other end is fixed on the inner wall of the conveying pipe 1. The reset spring 19 is used to drive the movable end 14 to move and reset. In this way, when the locking screw 15 is rotated back in actual use, the reset spring 19 is continuously compressed. When its elastic force is greater than the magnetic attraction force, the locking screw 15 is driven to separate from the connecting portion 16. At this time, the connecting portion 16 can move freely. At this time, the high-pressure gas introduced can push the guide plate 10 to move and flip around the hinge, thereby causing the peak 11 of the guide plate 10 to rise in height until it hits the partition 2. In this way, with the help of the guide plate 10, the knocking on the partition 2 can achieve the purpose of vibration, thereby allowing the powder remaining on the partition 2 to be released. It serves the purpose of clearing blockages and shaking off, and avoids blockages caused by long-term use; of course, the guide plate 10 can be manually driven by the locking screw 15 to move to achieve angle flip adjustment and change to hit the partition 2; after the high-pressure gas source is cut off from the air inlet 5, the connection part 16 will be reset under the tension of the reset spring 19, and the high-pressure gas source is introduced into the air inlet 5 in a cyclical manner to achieve the vibration of the gas guide 9 on the partition 2 to achieve the purpose of clearing powder and preventing blockage. No additional components are required during the process, and the operation is simple and convenient, realizing the multi-purpose of the gas guide 9; in addition, the trough 12 of the gas guide 9 can be used as a collection tank for receiving powder. The powder accumulated in the collection tank is not easily affected by the airflow and discharged from the air outlet 6, which is also convenient for subsequent unified removal and processing.

[0053] like Figure 2 and Figure 3 As shown, removable cover plates 20 are provided at both ends of the delivery pipe 1 corresponding to the gas delivery area 4, and the cover plate 20 and the delivery pipe 1 can be fixed by screws. The air inlet 5 and the locking screw 15 are both arranged on the cover plate 20. When it is necessary to take out the internal gas guide 9 later, it is only necessary to remove the cover plate 20, and the cover plate 20, the locking screw 15 and the gas guide 9 can be extracted together, so that a disposable overall extraction and removal is achieved. When the gas guide 9 is taken out, the powder that has been shaken off is taken out, so that the powder is uniformly taken out, and the operation is simple and convenient. The cover plate 20 at one end of the lower part can also be removed, and the gas guide 9 slides out from the lower end, synchronously taking out the internal powder.

[0054] The above are all preferred embodiments of the present application, and are not intended to limit the scope of protection of the present application. Therefore, any equivalent changes made based on the structure, shape, and principle of the present application should be included in the scope of protection of the present application.

Claims

1. A production process for a slow-release compound fertilizer, characterized in that: The following steps are involved: S1, preparation of various elemental raw materials; S2, granulating the elemental raw material to obtain elemental raw material particles; S3, coating the single-substance raw material particles with a sustained-release film according to design requirements to obtain sustained-release raw material particles; S4, mixing and drying the sustained-release raw material particles according to design requirements; S5, packaging to obtain the finished slow-release compound fertilizer.

2. The production process of a slow-release compound fertilizer according to claim 1, characterized in that: The elemental raw material particles obtained in step S2 are screened, and the elemental raw material particles that meet the particle size are transported to the silo for storage, and the elemental raw material particles that do not meet the particle size are used as raw materials for granulation again.

3. The production process of a slow-release compound fertilizer according to claim 1, characterized in that: In step S3, the sustained-release membrane coated with the same single-substance raw material particles has different release cycles.

4. The production process of a slow-release compound fertilizer according to claim 1, characterized in that: The diameter of the single-substance raw material particles is 3.3-4.7 mm and they are spherical.

5. The production process of a slow-release compound fertilizer according to claim 1, characterized in that: The sustained-release membrane in step S3 includes an initial sustained-release membrane, the material of which includes 5%-15% hydroxypropyl cellulose, 90%-80% ethanol, 2%-3% dispersant, 1%-2% plasticizer, and 0.5%-1% stabilizer, which are dissolved item by item in a reactor to form a film-forming solution.

6. The production process of a slow-release compound fertilizer according to claim 1, characterized in that: The slow-release film in step S3 includes a medium-term slow-release film, and the materials of the medium-term slow-release film include 5%-35% tung oil, 1%-5% turpentine, 30%-50% ethyl acetate, 20%-30% fatty acid triglyceride, 1%-2% defoaming agent, 1%-2% stabilizer, and 2%-3% film-forming aid, which are dissolved one by one in a reactor to form a film-forming solution.

7. The production process of a slow-release compound fertilizer according to claim 1, characterized in that: The sustained-release membrane in step S3 includes a late sustained-release membrane, and the materials of the late sustained-release membrane include 20%-40% sulfur, 5%-10% hydroxypropyl cellulose, 60%-80% carbon disulfide, 1%-2% defoaming agent, 1%-2% stabilizer, and 2%-3% film-forming aid, which are dissolved item by item in a reactor to form a film-forming solution.

8. The production process of a slow-release compound fertilizer according to claim 5, 6 or 7, characterized in that: The film-forming solution is evenly sprayed onto the fertilizer particle curtain lifted by the lifting plate in the drum through an atomizing device at an air pressure of 0.1-0.5 MPA, forming a complete slow-release film on the surface of the fertilizer particles.

9. The production process of a slow-release compound fertilizer according to claim 1, characterized in that: The raw material particles are transported between each process by a gas transport device, the gas transport device comprising a transport pipe (1), an axially arranged partition screen (2) is provided in the transport pipe (1), the upper portion of the partition screen (2) is a raw material particle transport area (3), the lower portion of the partition screen (2) is a gas transport area (4), an air inlet (5) and an air outlet (6) are respectively provided at both ends of the transport pipe (1), the air inlet (5) and the air outlet (6) are both communicated with the gas transport area (4), a material feed port (7) and a material outlet (8) are respectively provided at both ends of the top of the transport pipe (1), and the air inlet (5) is connected to a high-pressure gas source.

10. The production process of a slow-release compound fertilizer according to claim 5, characterized in that: A gas guide (9) is provided in the gas delivery area (4) of the delivery pipe (1). The gas guide (9) comprises guide plates (10) hinged to each other. The guide plates (10) are all tilted.

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