Clean production process of blended fertilizer

Abstract

The invention discloses a clean production process of a blended fertilizer, which comprises the following steps: preparing and selecting raw materials; performing primary granulation on different raw materials to obtain uniform granular raw materials; performing closed ventilation storage on the granular raw materials; proportioning and metering the granular raw materials; mixing and stirring; finally, packaging is carried out, 4-5 mm particles obtained after the raw materials are subjected to extrusion forming through a pair of rollers and subjected to primary granulation are consistent in appearance state, air in the raw materials is removed through extrusion, gaps are compressed, the density and specific gravity of the formed particles tend to be uniform, and the product quality is improved. Blending layering caused by particle size, density difference and different adsorption capacities cannot occur when the raw materials are blended, the blended compound fertilizer meets the international general blending fertilizer proportioning principle, the completely-homogenized blending fertilizer quality requirement can be met, the processing cost is saved, the production efficiency is improved, and the production cost is reduced. And the problem of caking of the raw materials is effectively solved.

Description

Technical Field

[0001] The invention relates to the field of fertilizer production, in particular to a clean production process of blended fertilizer. Background Art

[0002] Blended fertilizer, also known as BB fertilizer or dry mixed fertilizer, is a chemical fertilizer containing any two or three of the three nutrients of nitrogen, phosphorus and potassium. It is made from unit fertilizer or compound fertilizer through simple mechanical mixing. There is no significant chemical reaction during the mixing process. Blended fertilizer has the advantages of flexible nutrient allocation and low cost.

[0003] The production process of blended fertilizer mainly includes raw material selection, batching, mixing, packaging, etc. The production process is relatively simple, but the physical properties of different fertilizer raw materials are different. For example, the particle size and density of different fertilizer raw materials are different. These differences may cause agglomeration during storage, affecting the use of fertilizers. In addition, after mixing, there will be uneven nutrients. For example, large-particle fertilizer raw materials are located at the bottom, and small-particle fertilizer raw materials are located at the top, resulting in upper and lower stratification, which leads to excessive nutrients in some areas and insufficient nutrients in other areas during fertilization. Further improvement is needed. Summary of the invention

[0004] In order to further reduce the agglomeration of raw materials and the phenomenon of upper and lower stratification, the present application provides a clean production process for blended fertilizers.

[0005] The present application provides a clean production process for blended fertilizers, which adopts the following technical solutions: A clean production process for blended fertilizers comprises the following steps: S1, raw material preparation and selection; S2, granulating different raw materials once to obtain uniform granular raw materials; S3, the granular raw materials are stored in a closed and ventilated manner; S4, batching and metering the granular raw materials; S5, mixing and stirring; S6, packaging.

[0006] Optionally, step S2 uses a double-roll granulator to perform granulation, and the diameter of the granular raw material after one granulation is 4-5 mm.

[0007] Optionally, in step S3, a silo is used to store the granular raw material, and the silo is provided with a ventilation device and a dehumidification device.

[0008] Optionally, the stirring speed in step S5 is 8-30 rpm, and the stirring time is 8-15 minutes.

[0009] Optionally, the silo includes a silo body, a feed port is provided on a top side of the silo body, a discharge port is provided at the bottom of the silo body, a stop valve is provided at the discharge port, and a vibration motor is provided at the silo body corresponding to the discharge port.

[0010] Optionally, a spiral buffering drop chute is provided in the silo, the top end of the buffering drop chute is close to the feed port, the bottom end of the buffering drop chute is close to the discharge port, one side of the buffering drop chute is fixed to the inner wall of the silo, and the other side is provided with a guard edge.

[0011] Optionally, the dehumidification device adopts a dehumidifier, and the ventilation device includes a wind ball, which is arranged on the top of the warehouse body. The wind ball has a ventilation hole extending into the warehouse body, and a cloth bag is arranged at the ventilation hole. The cloth bag is used to suppress the dispersion of dust in the warehouse body.

[0012] Optionally, a chute gas conveying mechanism is used to feed materials between each step and process, and the chute gas conveying mechanism includes an inclined pipeline, one end of the pipeline is provided with a feed pipe, and the other end is provided with a discharge end, an isolation layer is provided in the pipeline, the upper part of the isolation layer is a material flow layer, and the lower part of the isolation layer is a compressed air flow layer, and the isolation layer is provided with evenly distributed through holes.

[0013] Optionally, the chute gas delivery mechanism also includes an air storage tank, an air intake pipe connecting the air storage tank and the pipeline is provided between the two, the air intake pipe is connected to the air storage tank and the compressed air flow layer, a return air pipe is provided at the lower end of the pipeline, one end of the return air pipe is connected to the compressed air flow layer, and the other end is connected to the air intake pipe, and both the air intake pipe and the return air pipe are provided with a one-way valve.

[0014] Optionally, the pipeline is a high-pressure vinyl chloride pipe or a high-pressure polypropylene pipe.

[0015] In summary, the present application includes at least one of the following beneficial technical effects: 1. The storage form of the new process can store granular raw materials in large quantities. The contact area between particles is reduced, the volume compression density is increased, and it is not easy for humid gas to enter. In addition, the use of ventilation and dehumidification devices not only greatly overcomes the problem of raw materials absorbing moisture and hardening due to bagging permeability, but also enhances the fluidity of raw materials, creating a foundation for the automation system of computer batching and electronic metering feeding; 2. The raw materials are extruded by rollers to form 4-5mm particles with uniform appearance. The air in the raw materials is removed by extrusion, and the gaps are compressed, so that the density and specific gravity of the formed particles tend to be uniform. This kind of raw materials will not cause stratification due to particle size, density difference and different adsorption capacity. The compound fertilizer after blending meets the internationally accepted principle of blended fertilizer ratio and can meet the quality requirements of fully homogenized blended fertilizer, which not only saves processing costs and improves production efficiency, but also enables the subsequent simple compound fertilizer to be realized, which may form a new fertilizer production model; 3. The new process has made a thorough improvement on the stubborn environmental pollution problem in the current production and transportation links. That is, a closed high-pressure vinyl chloride pipe or high-pressure polypropylene pipe is used as the main conveying body, and an isolation layer is lined inside. Compressed air is introduced to produce directional flow, driving the granular materials to flow smoothly along the set inclination angle. This new inclined trough inclination pipeline structure transportation overcomes the material blockage and solves the corrosion and environmental pollution problems commonly existing in inorganic salts in the raw materials of compound fertilizer production; 4. The new process can well meet the requirements of green factories and clean production, and effectively overcome a series of practical problems in the three traditional production methods (high tower granulation, agglomeration granulation, roller extrusion granulation), such as material overflow, dust splashing, material moisture absorption and adhesion to production equipment to form corrosion; 5. The new one-time granulation mode overcomes the product defects caused by various drawbacks of previous blended fertilizers and can fully realize the automated blended fertilizer production. From foreign examples, blended fertilizers are the most economical compound fertilizer production mode. This method may bring about beneficial changes in compound fertilizer production and promote the realization of intensive, simplified, low-energy and diversified compound fertilizer production; 6. This process is simple and efficient, with relatively few granulation equipment and auxiliary facilities, and the energy consumption is significantly lower than other types of production energy consumption, which directly reduces the production cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a flow chart of Example 1.

[0017] Figure 2 It is a structural diagram of the silo in Example 1.

[0018] Figure 3 It is a structural diagram of the buffering drop chute in Example 1.

[0019] Figure 4 It is a schematic diagram of the structure of the feeding device in Example 1.

[0020] Figure 5 It is a structural diagram of the chute gas delivery mechanism in Example 1.

[0021] Figure 6This is a partial structural diagram of the interior of the chute gas delivery mechanism in Example 2.

[0022] Figure 7 It is a cross-sectional view of the blockage clearing member in Example 2.

[0023] Figure 8 It is a structural diagram of the wind ball in Example 2.

[0024] Description of reference numerals: 1. Silo; 2. Silo body; 3. Feed port; 4. Discharge port; 5. Stop valve; 6. Buffer drop slide; 7. Sidewall; 8. Base frame; 9. Reinforcement rod; 10. Vibration motor; 11. Wind ball; 12. Bag; 13. Shell; 14. Elevator; 15. Chute gas conveying mechanism; 16. Pipeline; 17. Feed pipe; 18. Discharge end; 19. Isolation layer; 20. Material flow layer; 21. Compressed air flow layer; 2 2. Through hole; 23. Inlet pipe; 24. Air storage tank; 25. Return pipe; 26. One-way valve; 27. Pressure relief valve; 28. Clearing plate; 29. ​​Telescopic member; 30. Clearing rod; 31. Connecting spring; 32. Wind wheel; 33. Cam; 34. Conical tip; 35. Scraper; 36. Groove; 37. Return spring; 38. Fan blade; 39. Inclined surface; 40. Cylinder; 41. Mounting part; 42. Fan; 43. Rod. DETAILED DESCRIPTION

[0025] The following is combined with Figure 1-8 This application is described in further detail.

[0026] Example 1 A clean production process for blended fertilizers, such as Figure 1 As shown, it mainly includes the following steps: S1, preparation and selection of raw materials; The raw materials for the production of blended fertilizers or compound fertilizers are mostly inorganic salts, such as potassium sulfate, ammonium sulfate, potassium chloride, ammonium phosphate, potassium magnesium phosphate, ammonium bicarbonate, urea, etc. For example, the classic nitrogen, phosphorus and potassium nutrient combination ratio of compound fertilizer is 18-18-18, which means that it contains 18% nitrogen, 18% phosphorus pentoxide and 18% potassium oxide.

[0027] S2, primary granulation; Various raw materials are granulated by a double-roll granulator to obtain granular raw materials, and the diameter of the granular raw materials is 4-5 mm.

[0028] S3, closed and ventilated storage; The granular raw materials are transported to the silo 1 for sealed storage. The silo 1 is provided with a ventilation device and a dehumidification device to achieve ventilation and dehumidification of the silo 1.

[0029] S4, ingredient measurement; A computer-controlled automatic batching system is used to accurately feed the simple granular raw materials in the simple raw material warehouse into the batching storage box to form a basic weight unit. For example, the nitrogen, phosphorus and potassium nutrient ratio is 18-18-18. The computer batches the raw materials from the simple raw material warehouse that has undergone a single granulation of 4-5mm, and the electronic meter outputs 30 parts of urea, 42 parts of monoammonium phosphate, and 30 parts of potassium chloride.

[0030] S5, mixing and stirring; One basic weight unit of granular raw materials is conveyed into a mixer for stirring and mixing. The stirring time is 10 minutes and the stirring speed is 8-30 revolutions per minute.

[0031] S6, packaging; The evenly mixed granular raw materials are transferred to the packaging section for packaging, or they can be transferred to the finished product warehouse to be packed into bags according to demand.

[0032] like Figure 2 and Figure 3 As shown, the silo 1 in step S3 includes a vertical cylindrical silo body 2, the volume of the silo body 2 is generally within tens of cubic meters or even hundreds of cubic meters, a feed port 3 is opened on one side of the top of the silo body 2, the bottom of the silo body 2 is conical and is provided with a discharge port 4, a stop valve 5 is provided at the discharge port 4, and a spiral downward buffering drop chute 6 is provided inside the silo body 2, one side of the buffering drop chute 6 is fixed to the inner wall of the silo body 2, and the other side is provided with a retaining edge 7, the retaining edge 7 prevents the granular raw materials from escaping from the buffering drop chute 6 midway, so that the granular raw materials entering the silo body 2 can slowly fall to the bottom of the silo body 2 along the buffering drop chute 6, avoiding the situation where the granular raw materials are broken due to vertical falling, and when discharging is needed, only the stop valve 5 needs to be opened to discharge from the discharge port 4.

[0033] like Figure 2 and Figure 3 As shown, a base frame 8 for supporting the silo 2 is provided at the bottom, and a reinforcing rod 9 connecting the base frame 8 and the bottom of the silo 2 is provided. A vibration motor 10 is provided on the reinforcing rod 9. Through the design of the vibration motor 10, the vibration motor 10 generates vibration during discharging to prevent the problem of material accumulation at the discharge port 4 and resulting in poor discharging.

[0034] like Figure 2 and Figure 3As shown, a ventilation device and a dehumidification device are provided on the warehouse body 2. The dehumidification device adopts a dehumidifier, and dehumidification is performed inside the warehouse body 2 in the dehumidifier, so as to avoid the situation where the humidity inside the warehouse body 2 is too high. The ventilation device adopts a wind ball 11. The top of the warehouse body 2 is also designed in a cone shape. The wind ball 11 is arranged on the top of the warehouse body 2. With the help of the wind ball 11, good ventilation between the warehouse body 2 and the outside world is achieved, so as to achieve a good ventilation effect. In addition, a cloth bag 12 is arranged at the end of the wind ball 11 extending into the warehouse body 2. The cloth bag 12 is used to block the discharge of dust inside the warehouse body 2, so as to effectively prevent dust.

[0035] like Figure 2 and Figure 3 As shown, the inner wall of the bin body 2 and the surface of the buffer drop chute 6 are coated with a resin coating or a gas barrier coating to prevent moisture absorption and reduce friction. This storage method solves a series of drawbacks caused by the traditional fertilizer production enterprises storing bagged raw materials on high racks, which are very easy to absorb moisture, and the environment has been greatly improved.

[0036] This storage method for granular raw materials solves a series of drawbacks caused by the traditional fertilizer production enterprises storing bagged raw materials on high racks, which are very easy to absorb moisture, and the environment has been greatly improved.

[0037] like Figure 4 and Figure 5 As shown, the above steps and processes involve the transmission and delivery of granular raw materials. In this embodiment, a conveying device is used to transport the granular raw materials. The conveying device includes a shell 13 and an elevator 14 and a chute gas conveying mechanism 15 inside. The elevator 14 and the chute gas conveying mechanism 15 are located in the shell 13, so that the granular raw material transportation environment is in the closed shell 13, avoiding dust and effectively improving the workshop production environment. The elevator 14 and the chute gas conveying mechanism 15 are alternately connected and used. The elevator 14 mainly realizes lifting the granular raw materials from a low place to a high place, and then the granular raw materials fall from a high place into the chute gas conveying mechanism 15. The granular raw materials slide down to a low place under the action of their own gravity. This cycle can achieve closed transportation of the granular raw materials.

[0038] like Figure 5As shown, the chute gas delivery mechanism 15 includes an inclined pipeline 16, a feed pipe 17 is provided at one end of the pipeline 16 at a high position, a discharge end 18 is provided at one end of the pipeline 16 at a low position, and an isolation layer 19 is horizontally provided in the middle of the pipeline 16, a material flow layer 20 is provided above the isolation layer 19, and a compressed air flow layer 21 is provided below the isolation layer 19, and vertical through holes 22 are provided on the isolation layer 19, and the through holes 22 are evenly distributed on the isolation layer 19; in addition, an air inlet pipe 23 connected to the compressed air flow layer 21 is provided on the pipeline 16, and the air inlet pipe 23 is connected to the compressed air flow layer 21 at one end of the pipeline 16 at a high position, and the chute gas delivery mechanism 15 also includes a gas storage tank 24 Compressed gas is stored in the gas tank 24. The end of the air inlet pipe 23 away from the pipeline 16 is connected to the gas tank 24. The compressed air is continuously provided to the compressed air flow layer 21 through the gas tank 24. The flow of compressed air is used to promote the flow of particulate materials in the material flow layer 20. The pipeline 16 adopts a high-pressure vinyl chloride pipe or a high-pressure polypropylene pipe. This new type of inclined trough angle pipeline transportation overcomes the material blockage and solves the corrosion and environmental pollution problems commonly existing in inorganic salts in the raw materials of compound fertilizer production. On the one hand, the material can fall under the action of its own gravity, and on the other hand, the compressed air plays a further role in assisting the transportation of the material, ensuring that the particulate material can fall well and be transported forward.

[0039] like Figure 5 As shown, a return air pipe 25 connected to the lower end of the pipeline 16 is connected thereto, one end of the return air pipe 25 is in circulation with the compressed air flow layer 21 at the lower end of the pipeline 16, and the other end is connected to the intake pipe 23, so that part of the compressed air can be recycled and utilized, waste can be reduced, and the purpose of energy saving can be further achieved; in this embodiment, a one-way valve 26 is provided on the intake pipe 23 and the return air pipe 25, so that the compressed air can only flow in one direction to avoid backflow.

[0040] like Figure 4 As shown, a pressure relief valve 27 is provided on the shell 13. Since the compressed air in the air storage tank 24 is continuously provided to the pipeline 16, the pressure in the shell 13 will continue to increase. After reaching a certain pressure, the pressure can be released with the help of the pressure relief valve 27, so as to avoid the situation where the internal pressure of the shell 13 is too high. At the same time, a filter cloth for filtering dust is provided at the pressure relief valve 27. The filter cloth blocks the discharge of internal dust, so as to discharge the internal pressure while effectively preventing dust.

[0041] Example 2 A clean production process for blended fertilizers, such as Figure 6As shown, the difference between this embodiment and embodiment 1 mainly lies in the difference in the internal structure of the pipeline 16. In this embodiment, a clearing plate 28 is provided in the compressed air flow layer 21 in the pipeline 16. The clearing plate 28 is vertically movably connected to the bottom wall of the pipeline 16 through telescopic members 29 at both ends. A clearing rod 30 corresponding to and cooperating with each through hole 22 on the isolation layer 19 is provided on the top of the clearing plate 28. A connecting spring 31 connecting the clearing plate 28 and the bottom wall of the pipeline 16 is provided between the clearing plate 28 and the bottom wall of the pipeline 16. The connecting spring 31 is used to drive the clearing plate 28 to move downward and reset, that is, the connecting spring 31 is used to drive the clearing plate 28 to reset to a state where the clearing rod 30 is separated from the through hole 22. In addition, a connecting spring 31 is provided in the pipeline 16 to drive the clearing plate 28 toward the isolation layer 19. The driving member moves in the direction of the isolation layer 19. In this embodiment, the driving member adopts a wind wheel 32, which is arranged at the compressed air flow layer 21. The wind wheel 32 is driven to rotate as the compressed air flows. A cam 33 is arranged at the central axis of the wind wheel 32, so that the cam 33 can be driven to rotate continuously as the wind wheel 32 rotates. The cam 33 abuts against the unblocking plate 28 to drive it to move toward the isolation layer 19. The unblocking rod 30 is inserted into the through hole 22 to achieve effective unblocking of the through hole 22. The unblocking plate 28 continuously moves back and forth in this way, and the unblocking operation of the isolation layer 19 is well achieved. The structure is simple and no manual operation is required for unblocking. It is simple and convenient, and the conveying effect of the particulate material is avoided to be affected by the blockage of the through hole 22.

[0042] like Figure 7 As shown, the clearing rod 30 includes a conical tip 34 at the top, and the conical tip 34 makes it easier for the clearing rod 30 to be inserted into the through hole 22 to clear the blockage. In addition, scraping strips 35 are symmetrically arranged on both sides of the clearing rod 30, and the scraping strips 35 are horizontally slidably connected to the clearing rod 30. The clearing rod 30 is provided with a groove 36 for the scraping strip 35 to move inward, and a return spring 37 is arranged in the groove 36 to drive the scraping strip 35 to move outward. In this embodiment, the clearing rod 30 is rotatably connected to the clearing plate 28, and the bottom end of the clearing rod 30 passes through the rear end of the clearing plate 28 to be provided with a fan blade 38, and the fan blade 38 is also located in the compressed air flow layer 21. When compressed air circulates, the fan blades 38 are driven to rotate, thereby synchronously driving the clearing rod 30 to rotate. In this way, the clearing rod 30 can not only penetrate into the through hole 22 in the vertical direction to clear the blockage, but also can scrape the inner wall of the through hole 22 with the help of the scraping strips 35 on both sides during the rotation process, thereby achieving better clearing efficiency for the through hole 22 and a more comprehensive clearing effect. The movable scraping strip 35 is designed to meet the use of through holes 22 with different apertures and has better applicability. The top end of the scraping strip 35 has an inclined surface 39, and the inclination angle of the inclined surface 39 is consistent with the conical top 34, which is convenient for the clearing rod 30 to be better inserted into the through hole 22.

[0043] like Figure 6As shown, the wind wheel 32 is vertically lifted and connected to the pipe 16, and a cylinder 40 is provided on the pipe 16 for driving the wind wheel 32 to vertically lift and lower, so that the position of the wind wheel 32 can be adjusted. When there is no need to clear the blockage, the wind wheel 32 can be driven downward by the cylinder 40 so that the cam 33 does not contact the isolation layer 19, thereby maintaining a good ventilation effect of the isolation layer 19 and reducing the situation where the cam 33 contacts the clearing plate 28 and continuously generates impact noise.

[0044] like Figure 8 As shown, in this embodiment, the bottom end of the wind ball 11 has a mounting portion 41 for extending into the silo 1, and a fan 42 is arranged in the mounting portion 41. The air outlet direction of the fan 42 is toward the wind ball 11. With the help of further design of the fan 42, the air flow efficiency can be improved, and the ventilation effect of the wind ball 11 can be improved. The bottom end of the mounting portion 41 is a ventilation port, and a cloth bag 12 is arranged at the ventilation port. The cloth bag 12 is used to block and suppress the discharge of dust in the silo body 2, and dust is effectively prevented; in addition, a vertical rod 43 is arranged on the fan 42, and the bottom end of the rod 43 abuts against the cloth bag 12. The vibration generated when the fan 42 is working can be transmitted to the cloth bag 12 through the rod 43, causing the cloth bag 12 to shake, so that the dust adhering to the cloth bag 12 can be shaken off, avoiding the clogging of the cloth bag 12 to affect the ventilation effect, and realizing automatic clearing of the cloth bag 12.

[0045] The above are all preferred embodiments of the present application, and the protection scope of the present application is not limited thereto. Therefore, any equivalent changes made according to the structure, shape, and principle of the present application should be included in the protection scope of the present application.

Claims

1. A clean production process for blended fertilizer, characterized in that: The following steps are involved: S1, raw material preparation and selection; S2, granulating different raw materials once to obtain uniform granular raw materials; S3, the granular raw materials are stored in a closed and ventilated manner; S4, batching and metering the granular raw materials; S5, mixing and stirring; S6, packaging.

2. A clean production process for blended fertilizer according to claim 1, characterized in that: In step S2, a double-roll granulator is used for granulation, and the diameter of the granular raw material after the first granulation is 4-5 mm.

3. The clean production process of a blended fertilizer according to claim 1, characterized in that: In step S3, a silo (1) is used to store the granular raw material, and a ventilation device and a dehumidification device are provided on the silo (1).

4. The clean production process of a blended fertilizer according to claim 1, characterized in that: The stirring speed in step S5 is 8-30 rpm, and the stirring time is 8-15 minutes.

5. The clean production process of a blended fertilizer according to claim 3, characterized in that: The silo (1) comprises a silo body (2), a feed port (3) is provided on one side of the top of the silo body (2), a discharge port (4) is provided at the bottom of the silo body (2), a stop valve (5) is provided at the discharge port (4), and a vibration motor (10) is provided at the silo body (2) corresponding to the discharge port (4).

6. A clean production process for blended fertilizer according to claim 5, characterized in that: A spiral buffering drop chute (6) is arranged in the silo body (2), the top end of the buffering drop chute (6) is close to the feed port (3), the bottom end of the buffering drop chute (6) is close to the discharge port (4), one side of the buffering drop chute (6) is fixed to the inner wall of the silo body (2), and the other side is provided with a retaining edge (7).

7. The clean production process of blended fertilizer according to claim 5, characterized in that: The dehumidification device adopts a dehumidifier, and the ventilation device includes a wind ball (11), the wind ball (11) is arranged on the top of the warehouse body (2), the wind ball (11) has a ventilation hole extending into the warehouse body (2), and a cloth bag (12) is arranged at the ventilation hole, and the cloth bag (12) is used to suppress the dispersion of dust in the warehouse body (2).

8. The clean production process of a blended fertilizer according to claim 1, characterized in that: A chute gas conveying mechanism (15) is used to convey materials between various steps and processes. The chute gas conveying mechanism (15) comprises an inclined pipeline (16). A feed pipe (17) is provided at one end of the pipeline (16), and a discharge end (18) is provided at the other end. An isolation layer (19) is provided in the pipeline (16). A material flow layer (20) is provided above the isolation layer (19), and a compressed air flow layer (21) is provided below the isolation layer (19). The isolation layer (19) is provided with evenly distributed through holes (22).

9. A clean production process for blended fertilizer according to claim 8, characterized in that: The chute gas delivery mechanism (15) further comprises an air storage tank (24); an air intake pipe (23) is provided between the air storage tank (24) and the pipeline (16) to connect the two; the air intake pipe (23) is connected to the air storage tank (24) and the compressed air flow layer (21); a return air pipe (25) is provided at one end of the lower part of the pipeline (16); one end of the return air pipe (25) is connected to the compressed air flow layer (21), and the other end is connected to the air intake pipe (23); and both the air intake pipe (23) and the return air pipe (25) are provided with a one-way valve (26).

10. The clean production process of blended fertilizer according to claim 8, characterized in that: The pipeline (16) is made of a high-pressure vinyl chloride pipe or a high-pressure polypropylene pipe.

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