Fertilizer granulation equipment and method
By introducing equipment and methods for screening followed by crushing into the potash fertilizer granulation process, the problems of small production scale and over-crushing have been solved, improving the quality and yield of potash fertilizer granulation and achieving more efficient production capacity.
Patent Information
- Application Number
- CN202511605240.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-11-04
- Publication Date
- 2025-12-19
AI Technical Summary
The existing potash fertilizer granulation process has a small production scale, low granulation quality, and serious over-crushing, resulting in a low yield of qualified products.
The system employs a sequentially arranged powder fertilizer conveying device, roller granulation device, flake crusher, primary screening device, secondary screening device, and post-processing device. By screening before crushing, over-crushing is avoided, thus improving the separation efficiency of qualified products.
The single-line production capacity was increased to 320,000 tons/year, achieving a granulation capacity of one million tons of potash fertilizer per year, improving the quality and yield of qualified products, and expanding the overall production scale.
Smart Images
Figure CN121155428A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of fertilizer manufacturing technology, and in particular relates to a fertilizer granulation equipment and method. Background Technology
[0002] A common fertilizer granulation method is extrusion granulation, which uses mechanical force to compress powdered fertilizer into shape. The following explanation uses potash fertilizer as an example, but it's not limited to potash fertilizer. Current single-line production lines for potassium chloride granulation can have a maximum capacity of 250,000 tons / year. Existing potash fertilizer granulation processes can be implemented as follows... Figure 1 As shown, Figure 1 This is a schematic diagram of the existing potash fertilizer granulation process. Specifically, the steps are as follows:
[0003] (1) Powdered potassium chloride is directly fed from the previous drying section to the roller press for granulation. The temperature of the inlet powder is about 80℃ and the particle size is less than 1mm.
[0004] (2) Granulation is carried out using a roller press to compress powdered potassium chloride into lumps;
[0005] (3) Use a flask crusher to crush the lumpy potassium chloride into flask potassium chloride with a particle size of <40mm;
[0006] (4) Use an impact crusher to crush the <40mm flake potassium chloride into <4mm granular potassium chloride as much as possible, with the maximum particle size being 10mm.
[0007] (5) Using the primary screening process, potassium chloride particles with a diameter greater than 4 mm are screened out and returned to the impact crusher for further crushing;
[0008] (6) Using a two-stage screening process, potassium chloride particles smaller than 2 mm are screened out and returned to the roller press for granulation, while particles with a diameter of 2 mm to 4 mm are sent to the subsequent packaging process as the final product.
[0009] However, the existing processes still have the following drawbacks: the production scale is still relatively small, the granulation quality is not high enough, and the over-crushing phenomenon is relatively serious, resulting in a low yield of qualified products. Summary of the Invention
[0010] To address the aforementioned problems, this invention provides a fertilizer granulation equipment and method that can avoid over-crushing, improve the quality and yield of qualified products, and increase the overall production scale.
[0011] The present invention provides a fertilizer granulation equipment, comprising a powder fertilizer conveying device, a roller granulation device, a flake crusher, a primary screening device, a secondary screening device, and a post-processing device arranged in sequence.
[0012] The roller granulation device is used to press powdered fertilizer into block-shaped flakes;
[0013] The sheet crusher is used to crush the blocky sheet material into small pieces smaller than a first preset size and then feed them into the primary screening device;
[0014] The discharge end of the primary screening device is connected to the feed end of the primary crushing device. The primary crushing device is used to crush the small pieces larger than the second preset size into materials smaller than the second preset size. The second preset size is smaller than the first preset size. The discharge end of the primary crushing device is connected to the feed end of the primary screening device.
[0015] The undersize discharge end of the primary screening device is connected to the feed end of the secondary screening device, and is used to transport materials smaller than the second preset size to the secondary screening device;
[0016] The secondary screening device is a two-stage double-layer screen. The discharge end of the upper screen of the secondary screening device is connected to the inlet end of the secondary crushing device. It is used to transport materials larger than the third preset size to the secondary crushing device. The third preset size is smaller than the second preset size. The secondary crushing device is used to crush the material into materials smaller than the third preset size. The discharge end of the secondary crushing device is connected to the inlet end of the primary screening device.
[0017] The lower screen discharge end of the secondary screening device is connected to the powdered fertilizer conveying device, which is used to convey materials smaller than the fourth preset size to the powdered fertilizer conveying device and return them to the roller granulation device for regranulation. The fourth preset size is smaller than the third preset size.
[0018] The discharge end of the screen of the secondary screening device is connected to the post-processing device, which is used to transport materials with dimensions between the third preset size and the fourth preset size to the post-processing device for post-processing to obtain the final product.
[0019] Preferably, the above-mentioned fertilizer granulation equipment includes at least two sets of the secondary screening device and the secondary crushing device, and the undersize discharge end of the primary screening device is connected to multiple secondary screening devices by a first distributor.
[0020] Preferably, in the above-mentioned fertilizer granulation equipment, the powdered fertilizer conveying device includes a first bucket elevator.
[0021] Preferably, in the above-mentioned fertilizer granulation equipment, the powdered fertilizer conveying device further includes an iron remover connected to the first bucket elevator.
[0022] Preferably, in the above-mentioned fertilizer granulation equipment, the powdered fertilizer conveying device further includes a first scraper conveyor disposed below the iron remover. The first scraper conveyor is provided with at least three first gate valves, and a corresponding roller press granulation device is disposed below each first gate valve. The end of the first scraper conveyor is also connected to the end of the overflow bin and the end of the first screw device respectively via a second distributor. The lower part of the overflow bin is connected to the beginning of the first screw device via a second gate valve, and the first screw device is connected to the first bucket elevator.
[0023] Preferably, in the above-mentioned fertilizer granulation equipment, the post-processing device includes a polishing device connected to the discharge end of the screen of the secondary screening device.
[0024] Preferably, in the above-mentioned fertilizer granulation equipment, the post-processing device further includes a drying and cooling device connected to the polishing device.
[0025] Preferably, in the above-mentioned fertilizer granulation equipment, the post-processing device further includes a coating device connected to the drying and cooling device.
[0026] Preferably, in the above-mentioned fertilizer granulation equipment, the post-processing device further includes a packaging device connected to the coating device.
[0027] The present invention provides a fertilizer granulation method, utilizing the fertilizer granulation equipment as described in any of the above claims, comprising:
[0028] The powdered fertilizer is pressed into lumps or flakes using the roller granulation device.
[0029] The flask crusher is used to crush the flask into small pieces smaller than the first preset size and then convey them to the primary screening device.
[0030] The material on the screen of the primary screening device is conveyed to the feed end of the primary crushing device. The primary crushing device crushes the small pieces larger than the second preset size into materials smaller than the second preset size and then conveys them to the feed end of the primary screening device.
[0031] The material passing through the primary screening device is conveyed to the secondary screening device;
[0032] The material is fed from the upper screen of the secondary screening device, which is larger than the third preset size, to the secondary crushing device. The secondary crushing device crushes the material into a size smaller than the third preset size and then feeds it to the primary screening device.
[0033] The material screened by the lower screen of the secondary screening device, which is smaller than the fourth preset size, is conveyed to the powdered fertilizer conveying device and then returned to the roller granulation device for regranulation.
[0034] The material in the screen of the secondary screening device, whose size is between the third preset size and the fourth preset size, is transported to the post-processing device for post-processing to obtain the final product.
[0035] As described above, the fertilizer granulation equipment provided by the present invention includes, in sequence, a powdered fertilizer conveying device, a roller press granulation device, a flake crusher, a primary screening device, a secondary screening device, and a post-processing device; the roller press granulation device is used to press the powdered fertilizer into lumps; the flake crusher is used to crush the lumps into small pieces smaller than a first preset size and feed them into the primary screening device; the discharge end of the primary screening device is connected to the feed end of the primary crushing device, and the primary crushing device is used to crush the small pieces larger than a second preset size. The material is crushed into pieces smaller than the second preset size, which is smaller than the first preset size. The discharge end of the primary crushing device is connected to the feed end of the primary screening device. The undersize discharge end of the primary screening device is connected to the feed end of the secondary screening device, used to convey materials smaller than the second preset size to the secondary screening device. The secondary screening device is a two-stage double-layer screen, and the discharge end of the upper screen of the secondary screening device is connected to the feed end of the secondary crushing device, used to convey materials larger than the third preset size to the secondary crushing device. In the crushing device, the third preset size is smaller than the second preset size. The secondary crushing device is used to crush the material into particles smaller than the third preset size. The discharge end of the secondary crushing device is connected to the feed end of the primary screening device. The discharge end of the lower screen of the secondary screening device is connected to the powdered fertilizer conveying device, used to convey materials smaller than the fourth preset size to the powdered fertilizer conveying device and return them to the roller granulation device for re-granulation. The fourth preset size is smaller than the third preset size. The discharge end of the screen of the secondary screening device is connected to the post-processing device, used to convey materials with sizes between the third and fourth preset sizes to the post-processing device for post-processing to obtain the final product. It can be seen that this scheme adopts a screening-then-crushing method, which reduces the crushing ratio of the secondary crusher. It can separate the qualified particle size products from the material as much as possible without over-crushing, reducing the amount of over-crushing. Therefore, it can increase the capacity of qualified products on a single line. Thus, this equipment can avoid over-crushing problems, improve the quality and output of qualified products, and increase the overall production scale. The fertilizer granulation method provided by the present invention has the same advantages as the fertilizer granulation equipment described above. Attached Figure Description
[0036] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.
[0037] Figure 1 A schematic diagram of the existing potash fertilizer granulation process;
[0038] Figure 2 This is an overall schematic diagram of an embodiment of a fertilizer granulation device provided by the present invention;
[0039] Figure 3 A schematic diagram of the post-processing device composition of an embodiment of a fertilizer granulation equipment provided by the present invention;
[0040] Figure 4 This is a schematic diagram of an embodiment of a fertilizer granulation method provided by the present invention. Detailed Implementation
[0041] The core of this invention is to provide a fertilizer granulation equipment and method that can avoid the problem of over-crushing, improve the quality and yield of qualified products, and increase the overall production scale.
[0042] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0043] An example embodiment of the fertilizer granulation equipment provided by the present invention Figure 2 As shown, Figure 2This is a schematic diagram of an embodiment of a fertilizer granulation device provided by the present invention. The fertilizer granulation device may include, in sequence, a powdered fertilizer conveying device 1, a roller press granulation device 2, a flake crusher 3, a primary screening device 4, a secondary screening device 5, and a post-processing device 6. The powdered fertilizer conveying device 1 is used to convey powdered fertilizer into the fertilizer granulation device. This powdered fertilizer may be, but is not limited to, potassium fertilizer, and its source can be at least two types: one is powdered fertilizer added directly, and the other is powdered fertilizer returned from the granulation device. Furthermore, the entire device and its pipelines can be covered with a physical insulation layer to minimize temperature loss of the material during the conveying process and ensure... The temperature of the mixed powder entering the machine is between 120℃ and 140℃. This roller granulation device 2 is used to press the powdered fertilizer into lumps and flakes. After top degassing and spiral pre-compression, the powdered fertilizer enters two opposing rotating rollers and is instantly pressed into dense flakes under a linear pressure of 120MPa to 300MPa, which can take into account the advantages of energy saving, high purity and high strength. The aforementioned flake crusher 3 is used to crush the lumps and flakes into small pieces smaller than the first preset size and enter the primary screening device 4. Specifically, the lumps and flakes can be subjected to two impacts and shearing by a dual-shaft differential speed spiked bar or sawtooth moving knife + fixed knife to complete "coarse crushing → primary granulation". The first preset size can be, but is not limited to, 40mm. The aforementioned primary screening device The discharge end 401 of the screening device 4 is connected to the feed end 701 of the primary crushing device 7. This primary crushing device 7 is used to crush small pieces larger than the second preset size into materials smaller than the second preset size. This second preset size is smaller than the first preset size mentioned above, and it is the screen aperture size of the primary screening device 4. Moreover, the second preset size can be, but is not limited to, 10mm. The discharge end 702 of the primary crushing device 7 is connected to the feed end 402 of the primary screening device 4, so that screening is continued using the primary screening device 4. The discharge end 403 of the primary screening device 4 is connected to the feed end 501 of the secondary screening device 5, and is used to transport materials smaller than the second preset size to the secondary screening device. In device 5, this ensures that the size of the material entering the secondary screening device 5 is smaller than the second preset size, which can be 10mm. The secondary screening device 5 is a two-stage double-layer screen. The discharge end 502 of the upper screen of the secondary screening device 5 is connected to the feed end 801 of the secondary crushing device 8, which is used to transport materials larger than the third preset size to the secondary crushing device 8. The third preset size is smaller than the second preset size, and the third preset size can be 4mm. This secondary crushing device 8 is used to crush the material into materials smaller than the third preset size. The discharge end 802 of the secondary crushing device 8 is connected to the feed end 402 of the primary screening device 4, so as to screen it again.The lower screen discharge end 502 of the secondary screening device 5 is connected to the powdered fertilizer conveying device 1. It is used to convey materials smaller than the fourth preset size to the powdered fertilizer conveying device 1 and return them to the roller granulation device for re-granulation. The fourth preset size is smaller than the third preset size, and this fourth preset size can be 2mm. In other words, materials smaller than the fourth preset size do not meet product requirements and therefore must be returned to the granulation equipment for re-granulation. The middle screen discharge end 503 of the secondary screening device 5 is connected to the post-processing device 6. It is used to convey materials with sizes between the third and fourth preset sizes to the post-processing device 6 for post-processing to obtain the final product. It should be noted that the upper screen of this secondary screening device 5 has a third preset size, and the lower screen has a fourth preset size. This allows materials between these two sizes to be screened out as meeting the size requirements of the final product. These materials are then post-processed to obtain the final product.
[0044] It should also be noted that the primary crushing unit 7 and the secondary crushing unit 8 can use toothed roller crushers instead of impact crushers, thereby reducing over-crushing of materials. This is mainly because the crushing principles of toothed roller crushers and impact crushers are different. Impact crushers use a high-speed rotating rotor to drive hammers, which impact the material at high speed, causing the material to repeatedly collide and crush between the hammers and the impact plates, ultimately achieving the desired particle size. Toothed roller crushers use two relatively rotating toothed rollers (or a single toothed roller and a liner) to compress, split, and shear the material. For lumpy potassium chloride to be extruded and granulated, the collision and impact of impact crushers are more likely to cause over-crushing of potassium chloride. With the above equipment, the single roller granulation capacity can be increased from 250,000 tons / year to 320,000 tons / year. By integrating three roller granulation lines and a post-processing system, a granulation capacity of one million tons of potash fertilizer per year can be achieved.
[0045] As described above, the fertilizer granulation equipment provided by the present invention includes, in sequence, a powdered fertilizer conveying device, a roller press granulation device, a flake crusher, a primary screening device, a secondary screening device, and a post-processing device. The roller press granulation device is used to press the powdered fertilizer into lumps and flakes. The flake crusher is used to crush the lumps and flakes into small pieces smaller than a first preset size and feed them into the primary screening device. The discharge end of the primary screening device is connected to the feed end of the primary crushing device. The primary crushing device is used to crush small pieces larger than a second preset size into materials smaller than the second preset size, where the second preset size is smaller than the first preset size. The discharge end of the primary crushing device is connected to the feed end of the primary screening device. The discharge end of the primary screening device is connected to the feed end of the secondary screening device, used to convey materials smaller than the second preset size to the secondary screening device. The secondary screening device is a two-stage double-layer screen, and the discharge end of the upper screen of the secondary screening device is connected to the feed end of the secondary crushing device. The first-stage screening unit has a discharge end for conveying materials larger than the third preset size to the second-stage crushing unit. The third preset size is smaller than the second preset size. The second-stage crushing unit crushes the materials into particles smaller than the third preset size. The discharge end of the second-stage crushing unit is connected to the feed end of the first-stage screening unit. The discharge end of the lower screen of the second-stage screening unit is connected to the powdered fertilizer conveying unit, which conveys materials smaller than the fourth preset size to the powdered fertilizer conveying unit and returns them to the roller granulation unit for re-granulation. The fourth preset size is smaller than the third preset size. The discharge end of the screen of the second-stage screening unit is connected to the post-processing unit, which conveys materials with sizes between the third and fourth preset sizes to the post-processing unit for post-processing to obtain the final product. It can be seen that this scheme adopts a screening-then-crushing method, which can separate the qualified particle size products from the material as much as possible without over-crushing. Thus, this equipment can avoid the problem of over-crushing, improve the quality and output of qualified products, and increase the overall production scale.
[0046] In one specific embodiment of the above-mentioned fertilizer granulation equipment, refer to... Figure 2 The equipment may include at least two sets of secondary screening devices 5 and secondary crushing devices 8, and the under-screen discharge end 403 of the primary screening device 4 is connected to multiple secondary screening devices 5 by the first distributor 9, which can further improve the efficiency of secondary screening and increase output. Moreover, it can be set to two, three or more sets according to actual needs, which is not limited here.
[0047] In another specific embodiment of the above-mentioned fertilizer granulation equipment, please continue to refer to... Figure 2The aforementioned powdered fertilizer conveying device 1 may include a first bucket elevator 101, specifically a raw material bucket elevator, which can efficiently transport materials. Furthermore, the powdered fertilizer conveying device 1 may also include an iron remover 102 connected to the first bucket elevator 101. This iron remover 102 can remove impurities from the material, preventing them from being introduced into the final fertilizer and causing pollution.
[0048] In another specific embodiment of the above-mentioned fertilizer granulation equipment, please refer to... Figure 2 The powdered fertilizer conveying device 1 may also include a first scraper conveyor 103 located below the iron remover 102. The first scraper conveyor 103 is provided with at least three first gate valves 104, and a corresponding roller press granulation device 2 is provided below each first gate valve 104. The end of the first scraper conveyor 103 is also connected to the overflow bin 106 and the end 1071 of the first screw device 107 respectively via a second distributor 105. The lower part of the overflow bin 106 is connected to the beginning 1072 of the first screw device 107 via a second gate valve 108, and the first screw device 107 is connected to the first bucket elevator 101. In this case, one first scraper conveyor 103 can transport the material to at least three roller presses. Excess material is transported to the overflow chamber 106, and then sent back to the inlet of the roller press granulation device 2 after the second gate valve 108 of the overflow chamber 106 is opened. It can be seen that this realizes the recycling of excess material, which is conducive to the smooth progress of the entire granulation process and will not cause abnormal material blockage.
[0049] refer to Figure 3 , Figure 3 This is a schematic diagram of the post-processing device composition of an embodiment of a fertilizer granulation equipment provided by the present invention. In the above-mentioned fertilizer granulation equipment, the post-processing device 6 may include a polishing device 601 connected to the discharge end 503 of the secondary screening device 5. Further, the post-processing device 6 may also include a drying and cooling device 602 connected to the polishing device 601. Even further, the post-processing device 6 may also include a coating and wrapping device 603 connected to the drying and cooling device 602. Still further, the post-processing device 6 may also include a packaging device 604 connected to the coating and wrapping device 603.
[0050] In this process, the finished granular material from the crushing and screening system is fed into a polishing drum via a belt conveyor. After water-spray polishing, the wear resistance and smoothness of the granular material increase. It is then sent to a rotary drying system to dry the product's moisture content to <0.2%. The dried granular product is cooled to <65°C by a vertical cooler and then fed into a coating roller via a belt conveyor. A mixed solution of anti-caking agent and anti-powdering agent is added for coating treatment, and then the product is discharged from the drum discharge port as the final granular product, which is sent to the subsequent packaging process. By setting up a polishing process, a small amount of water is sprayed to fill and dissolve the surface gaps of the granules. Then, the surface of the granules is polished by rolling to remove the sharp edges. Finally, the surface is dried to recrystallize and form a dense crystalline layer. This further improves the quality of the product and prevents the granular potassium chloride from easily breaking and producing fine powder during storage and transportation, as is the case in existing technologies.
[0051] An example of the fertilizer granulation method provided by this invention. Figure 4 As shown, Figure 4 This is a schematic diagram of an embodiment of a fertilizer granulation method provided by the present invention. The method utilizes the fertilizer granulation equipment as described in any of the above claims and may include the following steps:
[0052] S1: Use a roller granulation device to press powdered fertilizer into block-shaped flakes;
[0053] Specifically, powdered fertilizer can be degassed at the top and pre-compressed by a spiral before entering two opposing rotating rollers. Under a linear pressure of 120MPa to 300MPa, it is instantly pressed into dense sheets, which can take into account the advantages of energy saving, high purity and high strength.
[0054] S2: Use a shredder to crush the lumpy material into smaller pieces than the first preset size and then convey them to the primary screening device;
[0055] Specifically, the blocky sheet material can be subjected to two impacts and shearing processes by a dual-axis differential speed spike bar or sawtooth moving blade + fixed blade to complete "coarse crushing → primary granulation". The first preset size can be, but is not limited to, 40mm.
[0056] S3: The material on the screen of the primary screening device is conveyed to the feed end of the primary crushing device. The primary crushing device crushes small pieces larger than the second preset size into materials smaller than the second preset size and conveys them to the feed end of the primary screening device.
[0057] This second preset size is smaller than the first preset size mentioned above. It is the screen aperture size of the primary screening device 4, and the second preset size can be, but is not limited to, 10mm. Moreover, it is conveyed to the feed end of the primary screening device, so that screening can continue using the primary screening device.
[0058] S4: Convey the material under screening from the primary screening device to the secondary screening device;
[0059] This ensures that the size of the material entering the secondary screening device is smaller than the second preset size, which can be 10mm.
[0060] S5: The material from the upper screen of the secondary screening device, which is larger than the third preset size, is conveyed to the secondary crushing device. The secondary crushing device crushes the material into a size smaller than the third preset size and then conveys it to the primary screening device.
[0061] The third preset size is smaller than the second preset size, and the third preset size can be 4mm. When it is conveyed to the primary screening device, it can be screened again.
[0062] S6: The material screened by the lower screen of the secondary screening device that is smaller than the fourth preset size is conveyed to the powdered fertilizer conveying device and returned to the roller granulation device for regranulation.
[0063] The fourth preset size is smaller than the third preset size, and the fourth preset size can be 2mm. In other words, materials smaller than the fourth preset size do not meet the product requirements, so they must be returned to the granulation equipment for regranulation.
[0064] S7: The material in the screen of the secondary screening device with dimensions between the third and fourth preset dimensions is transported to the post-processing device for post-processing to obtain the final product.
[0065] It should be noted that the upper screen of this two-stage screening device has a third preset screen size, and the lower screen has a fourth preset screen size. This allows materials between these two sizes to be screened out as the size that meets the requirements of the final product. These materials can then be post-processed to obtain the final product.
[0066] In summary, the fertilizer granulation method described above adopts a screening-then-crushing approach, which reduces the crushing ratio of the secondary crusher. This allows for the separation of qualified particle sizes from the material while avoiding over-crushing, thus reducing the amount of over-crushed material. Consequently, it can increase the production capacity of qualified products on a single production line. Therefore, this method can avoid over-crushing, improve the quality and yield of qualified products, and enhance the overall production scale.
[0067] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims
1. A fertilizer granulation device, characterized in that, It includes a powdered fertilizer conveying device, a roller granulation device, a flake crusher, a primary screening device, a secondary screening device, and a post-processing device arranged in sequence; The roller granulation device is used to press powdered fertilizer into block-shaped flakes; The sheet crusher is used to crush the blocky sheet material into small pieces smaller than a first preset size and then feed them into the primary screening device; The discharge end of the primary screening device is connected to the feed end of the primary crushing device. The primary crushing device is used to crush the small pieces larger than the second preset size into materials smaller than the second preset size. The second preset size is smaller than the first preset size. The discharge end of the primary crushing device is connected to the feed end of the primary screening device. The undersize discharge end of the primary screening device is connected to the feed end of the secondary screening device, and is used to transport materials smaller than the second preset size to the secondary screening device; The secondary screening device is a two-stage double-layer screen. The discharge end of the upper screen of the secondary screening device is connected to the feed end of the secondary crushing device. It is used to transport materials larger than the third preset size to the secondary crushing device. The third preset size is smaller than the second preset size. The secondary crushing device is used to crush the material into materials smaller than the third preset size. The discharge end of the secondary crushing device is connected to the feed end of the primary screening device. The lower screen discharge end of the secondary screening device is connected to the powdered fertilizer conveying device, which is used to convey materials smaller than the fourth preset size to the powdered fertilizer conveying device and return them to the roller granulation device for regranulation. The fourth preset size is smaller than the third preset size. The discharge end of the screen of the secondary screening device is connected to the post-processing device, which is used to transport materials with dimensions between the third preset size and the fourth preset size to the post-processing device for post-processing to obtain the final product.
2. The fertilizer granulation equipment according to claim 1, characterized in that, It includes at least two sets of the secondary screening device and the secondary crushing device, and the undersize discharge end of the primary screening device is connected to multiple secondary screening devices by a first distributor.
3. The fertilizer granulation equipment according to claim 1, characterized in that, The powdered fertilizer conveying device includes a first bucket elevator.
4. The fertilizer granulation equipment according to claim 3, characterized in that, The powdered fertilizer conveying device also includes an iron remover connected to the first bucket elevator.
5. The fertilizer granulation equipment according to claim 4, characterized in that, The powdered fertilizer conveying device also includes a first scraper conveyor located below the iron remover. The first scraper conveyor is equipped with at least three first gate valves, and a corresponding roller granulation device is located below each first gate valve. The end of the first scraper conveyor is connected to the overflow bin and the end of the first screw device via a second distributor. The lower part of the overflow bin is connected to the beginning of the first screw device via a second gate valve, and the first screw device is connected to the first bucket elevator.
6. The fertilizer granulation equipment according to any one of claims 1-5, characterized in that, The post-processing device includes a polishing device connected to the discharge end of the screen of the secondary screening device.
7. The fertilizer granulation equipment according to claim 6, characterized in that, The post-processing device also includes a drying and cooling device connected to the polishing device.
8. The fertilizer granulation equipment according to claim 7, characterized in that, The post-processing device also includes a coating wrapping device connected to the drying and cooling device.
9. The fertilizer granulation equipment according to claim 8, characterized in that, The post-processing device also includes a packaging device connected to the coating wrapping device.
10. A method for granulating fertilizer, characterized in that, The fertilizer granulation equipment according to any one of claims 1-9 comprises: The powdered fertilizer is pressed into lumps or flakes using the roller granulation device. The flask crusher is used to crush the flask into small pieces smaller than the first preset size and then convey them to the primary screening device. The material on the screen of the primary screening device is conveyed to the feed end of the primary crushing device. The primary crushing device crushes the small pieces larger than the second preset size into materials smaller than the second preset size and then conveys them to the feed end of the primary screening device. The material passing through the primary screening device is conveyed to the secondary screening device; The material is fed from the upper screen of the secondary screening device, which is larger than the third preset size, to the secondary crushing device. The secondary crushing device crushes the material into a size smaller than the third preset size and then feeds it to the primary screening device. The material screened by the lower screen of the secondary screening device, which is smaller than the fourth preset size, is conveyed to the powdered fertilizer conveying device and then returned to the roller granulation device for regranulation. The material in the screen of the secondary screening device, whose size is between the third preset size and the fourth preset size, is transported to the post-processing device for post-processing to obtain the final product.