Urea granulator, granulation system and process based on spiral material distribution spray head

Abstract

The invention discloses a urea granulator based on a spiral material distribution nozzle, a granulation system and a process, the granulator comprises a fluidized bed shell, the top of the fluidized bed shell is provided with the material distribution nozzle, the material distribution nozzle is communicated with a nozzle feed pipe, the inner wall surface of the fluidized bed shell is sequentially provided with multiple layers of urea nozzles from top to bottom, and the urea nozzles are communicated with the nozzle feed pipe. An air inlet and a discharge hole are formed in the bottom of the fluidized bed; a plurality of layers of spiral material curtain cavities are sequentially arranged in the material distribution spray head from top to bottom, and the spiral material curtain cavities are communicated with the spray head feeding pipe; through the synergistic effect of the multiple layers of spiral conical material curtain material distribution nozzles and the multiple layers of urine nozzles which are distributed in a staggered mode, efficient wrapping and uniform growth of urea particles are achieved.

Description

Technical Field

[0001] The present invention belongs to the technical field of large - particle chemical fertilizer production, and specifically relates to a urea spiral cloth - spraying nozzle, a granulator, a granulation system and a process. Background Art

[0002] The statements here only provide background art related to the present invention and do not necessarily constitute prior art.

[0003] In the production process of large - particle urea chemical fertilizer, the choice of granulation process directly affects product quality, energy consumption and production efficiency. At present, the industry mainly adopts three processes: pan granulation, drum granulation and fluidized - bed granulation. However, all of them have technical defects to varying degrees, which restrict production efficiency and energy utilization rate.

[0004] Among them, pan granulation is one of the earliest processes applied to urea particle forming. Its core equipment is an inclined - rotating disc granulator. Seed particles (small - particle urea) roll in the disc, and at the same time, urine is sprayed to make the particles gradually agglomerate and increase. However, due to the difficult - to - accurately - control movement trajectory of materials in the disc, the particle uniformity is poor and the qualified product rate is low. In addition, the adjustment ranges of the disc rotation speed and urine spraying amount are limited, and the production capacity of a single device is usually low. Drum granulation is a currently widely - applied large - particle urea production technology. It uses a large rotary cylinder, and through internal lifters, the seed particles are mixed with urine and rolled into particles. Although this process has improvements compared with pan granulation, there are still the following problems: the driving motor power of the drum is as high as hundreds of kilowatts, and the running power consumption is extremely high. In addition, the particles in the drum mainly rely on rolling agglomeration, the internal structure is loose, and the compressive strength is relatively low, and it is easy to break during transportation. Fluidized - bed granulation technology suspends seed particles through air flow and sprays urine to make it coat and grow. In theory, it can improve particle uniformity and strength. However, the existing fluidized - bed granulation devices still have the following technical bottlenecks: the traditional single - layer nozzle design is prone to cause the urine spray to penetrate the material curtain, and part of the urine directly contacts the wall to form scale, with the utilization rate less than 70%; when the seed distribution is uneven, the urine spray may locally penetrate the material curtain, resulting in incomplete particle forming; the tail gas containing dust and urea discharged from the fluidized bed needs to be washed through multiple stages, otherwise it is easy to block the pipeline, increasing the environmental protection treatment cost.

[0005] In summary, the current large - particle urea production processes generally face the following challenges:

[0006] 1. Traditional nozzles can only form a single - layer or simple multi - layer material curtain, with low urine wrapping efficiency and insufficient seed utilization rate. 2. The power consumption of equipment such as drum drive and fluidized - bed fan accounts for more than 30% of the production cost. 3. Problems such as equipment scaling and nozzle blockage lead to frequent shutdowns, and the annual effective production time is less than 80%. 4. It is difficult to completely recover the urea dust and ammonia emissions in the tail gas, increasing the burden of wastewater treatment. Summary of the Invention

[0007] The object of the present invention is to provide a urea granulator, granulation system and process based on a spiral cloth spray head. Through the synergistic effect of a multi-layer spiral conical material curtain cloth spray head and multi-layer urine nozzles with staggered distribution, efficient wrapping and uniform growth of urea particles are achieved.

[0008] To achieve the above object, the present invention is realized through the following technical solutions:

[0009] In a first aspect, an embodiment of the present invention provides a urea granulator based on a spiral cloth spray head, including a fluidized bed housing. A cloth spray head is provided at the top of the fluidized bed housing, and the cloth spray head is communicated with a spray head feed pipe. On the inner wall surface of the fluidized bed housing, multiple layers of urine nozzles are sequentially arranged from top to bottom. An air inlet and a discharge port are provided at the bottom of the fluidized bed; multiple layers of spiral material curtain cavities are sequentially arranged from top to bottom in the cloth spray head, and the spiral material curtain cavities are communicated with the spray head feed pipe.

[0010] As a further technical solution, adjacent spiral material curtain cavities are separated by baffles. The baffles are inclined, the top of the baffle extends into the spray head feed pipe, and the lengths of multiple baffles extending into the spray head feed pipe increase sequentially from top to bottom.

[0011] As a further technical solution, the spiral material curtain cavities include a first spiral material curtain cavity, a second spiral material curtain cavity, a third spiral material curtain cavity and a central material curtain cavity. The first spiral material curtain cavity and the second spiral material curtain cavity are separated by a first baffle, the second spiral material curtain cavity and the third spiral material curtain cavity are separated by a second baffle, and the third spiral material curtain cavity and the central material curtain cavity are separated by a third baffle.

[0012] As a further technical solution, the inlets of the first spiral material curtain cavity, the second spiral material curtain cavity and the third spiral material curtain cavity are all communicated with the outlets on the pipe wall of the spray head feed pipe, and the inlet of the central material curtain cavity is communicated with the outlet at the bottom of the spray head feed pipe.

[0013] As a further technical solution, the cloth spray head is fixedly connected to the spray head feed pipe. The spray head feed pipe is connected to the output shaft of a material curtain spray head motor through a gear transmission mechanism. The material curtain spray head motor is located outside the fluidized bed housing, and a seed feed pipe extends into the interior of the spray head feed pipe.

[0014] As a further technical solution, adjacent two layers of urine nozzles among the multiple layers of urine nozzles are staggered in the vertical direction, and the distance between adjacent two layers of spray heads is greater than the maximum spray angle of the urine nozzles.

[0015] In a second aspect, an embodiment of the present invention provides a urea granulation system, which includes the urea granulator described in the first aspect, and further includes a tail gas scrubbing tower, an intermediate bucket elevator, a screening device, and a return bucket elevator; the tail gas scrubbing tower is connected to the air outlet at the top of the fluidized bed housing through a draft fan, the inlet of the intermediate bucket elevator is connected to the discharge port at the bottom of the fluidized bed housing, the outlet of the intermediate bucket elevator is connected to the screening device, the granular outlet of the screening device is connected to the granular packaging device, and the return material outlet of the screening device is connected to the nozzle feed pipe at the top of the fluidized bed housing through the return bucket elevator.

[0016] As a further technical solution, the air inlet at the bottom of the fluidized bed housing is connected to a blower, and the urine nozzles on the inner wall surface of the fluidized bed housing are connected to the molten urea supply device through pipelines.

[0017] In a third aspect, an embodiment of the present invention provides a urea granulation process, including:

[0018] The seed granular urea forms a multi-layer spiral conical material curtain under the action of the cloth spraying nozzle. During the falling process of the granular urea, it forms large particles under the wrapping action of the urine sprayed by the multi-layer urine nozzles and falls to the bottom of the fluidized bed. After being cooled by the air inlet at the bottom of the fluidized bed, it is discharged through the discharge port.

[0019] The discharged material is lifted by the intermediate bucket elevator and enters the screening device for screening. The finished large particles enter the finished product packaging system through the conveyor belt; the small particles after being screened by the screening device are lifted by the return bucket elevator and enter the seed bin and fresh seeds together and enter the cloth spraying nozzle to achieve continuous production.

[0020] As a further technical solution, the hot air and dust of the granulator are sent to the tail gas scrubbing tower by the draft fan for washing, and when the urine concentration reaches the requirement, it is pumped back to the evaporation system of the urea plant by the washing pump.

[0021] The beneficial effects of the above embodiments of the present invention are as follows:

[0022] The urea granulator provided by the present invention realizes the efficient wrapping and uniform growth of urea particles through the coordinated action of the multi-layer spiral conical material curtain cloth spraying nozzle and the multi-layer urine nozzles with staggered distribution. The cloth spraying nozzle is designed as a multi-layer spiral material curtain cavity (including the central material curtain), and the distribution of seeds is precisely controlled through baffles to form a spiral conical material curtain with adjustable thickness and uniform density. The multi-layer urine nozzles are staggered in the vertical direction, and the spacing is greater than the outer arc of the spray angle, ensuring that each layer of spray independently covers different areas of the material curtain. Fundamentally solving the key technical problems such as easy penetration of the material curtain and uneven wrapping existing in the traditional urea granulation process.

[0023] The urea granulation system provided by the present invention includes a fluidized bed, a screening device, a bucket elevator device, a washing device, etc. It realizes nearly zero waste through two-stage screening - return bucket elevator - tail gas washing. The hot air containing urea dust generated during the granulation process is drawn into the tail gas washing tower by an induced draft fan, and urine is recovered through water washing. After the concentration of the washing liquid reaches the standard, it is pumped back to the evaporation system for reuse. The air intake of the fluidized bed can also be interlocked and regulated with the urine nozzle. When the particle temperature is detected to be on the high side, the air volume is automatically increased and the number of nozzles opened is reduced, so that the energy consumption is always in the optimal range.

[0024] The inner wall of the fluidized bed of the present invention adopts a silicon carbide-based composite coating to reduce the scaling rate. At the same time, the variable-frequency speed-regulating cloth spraying nozzle can adjust the thickness of the material curtain in real time, and the redundant urine nozzles support online switching and maintenance. Brief Description of the Drawings

[0025] The specification drawings forming a part of the present invention are used to provide a further understanding of the present invention. The schematic embodiments and descriptions thereof of the present invention are used to explain the present invention and do not constitute an improper limitation to the present invention.

[0026] Figure 1 is a schematic structural diagram of a urea granulator based on a spiral cloth spraying nozzle of the present invention;

[0027] Figure 2 is a schematic structural diagram of the spiral cloth spraying nozzle of the present invention;

[0028] Figure 3 is a working principle diagram of the urea granulation system of the present invention.

[0029] The schematic diagrams are only for illustration;

[0030] Among them, 1. Motor of the material curtain spraying nozzle; 2. Seed feeding pipe; 3. Air intake; 4. Cloth spraying nozzle; 5. Urine nozzle; 6. Bottom of the fluidized bed; 7. Discharge port; 8. Air inlet; 9. Nozzle feeding pipe; 10. First spiral material curtain cavity; 11. Second spiral material curtain cavity; 12. Third spiral material curtain cavity; 13. Central material curtain cavity; 14. First baffle; 15. Second baffle; 16. Third baffle; 17. Urea granulator; 18. Blower; 19. Tail gas washing tower; 20. Induced draft fan; 21. Seed material bin; 22. First screening device; 23. Second screening device; 24. Return bucket elevator; 25. Intermediate bucket elevator. Detailed Description of the Embodiments

[0031] It should be noted that the following detailed descriptions are all exemplary and are intended to provide further explanations of the present invention. Unless otherwise specified, all technical and scientific terms used in the present invention have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present invention belongs.

[0032] Example 1

[0033] In a typical embodiment of the present invention, a urea granulator based on a spiral cloth spray head is provided. As shown in Figure 1 and Figure 2 , it includes a fluidized bed housing. A cloth spray head 4 is arranged at the top of the fluidized bed housing. The cloth spray head 4 is communicated with a spray head feed pipe 9. On the inner wall surface of the fluidized bed housing, multiple layers of urine nozzles 5 are arranged in sequence from top to bottom. An air inlet and a discharge port 7 are arranged at the bottom 6 of the fluidized bed. In the cloth spray head 4, multiple layers of spiral material curtain cavities are arranged in sequence from top to bottom. The spiral material curtain cavities are communicated with the spray head feed pipe 9.

[0034] Through the multiple layers of spiral material curtain cavities of the above-mentioned urea granulator's spiral cloth spray head, seed particles form a dense and uniform conical material curtain during the falling process. The spraying of the urine nozzles can fully wrap the seed particles, greatly reducing raw material loss. In addition, due to the more uniform distribution of the multiple layers of spiral material curtains, the wrapping of the seed particles by the urine spray is more complete, the particle size distribution of the produced urea particles is narrower, and the particle strength is significantly improved, reducing the breakage rate during transportation.

[0035] In this embodiment, adjacent spiral material curtain cavities are separated by baffles. The top of the baffle extends into the spray head feed pipe, and the lengths of multiple baffles extending into the spray head feed pipe increase in sequence from top to bottom. By setting the baffles, the seed flow can be accurately distributed, ensuring the stable supply of seeds for each layer of spiral material curtain, avoiding the phenomenon of "material curtain holes", and improving the granulation uniformity. The stepped extension structure of the baffle can make the seeds buffer and fall layer by layer, avoiding direct impact on the bottom cavity, reducing the probability of blockage. At the same time, the inclination angle of the baffle matches the fluidity of the seeds, ensuring that the particles smoothly enter each layer of material curtain cavity and maintaining continuous production. In addition, the baffle is not only used for flow splitting, but also can be used as a support structure, improving the overall mechanical strength of the cloth spray head, preventing deformation during high-speed rotation, and extending the service life of the equipment.

[0036] In this embodiment, the cloth spray head is overall conical. The number of spiral material curtain layers of the cloth spray head can be adjusted according to the production load (such as 2 - 4 layers), and the urine nozzles can also be controlled layer by layer, enabling the device to flexibly respond to different production capacity requirements and being applicable to small, medium-sized to large urea production devices.

[0037] In a specific implementation manner of this embodiment, the spiral material curtain cavities include a first spiral material curtain cavity 10, a second spiral material curtain cavity 11, a third spiral material curtain cavity 12, and a central material curtain cavity 13. The first spiral material curtain cavity 10 and the second spiral material curtain cavity 11 are separated by a first baffle 14. The second spiral material curtain cavity 11 and the third spiral material curtain cavity 12 are separated by a second baffle 15. The third spiral material curtain cavity 12 and the central material curtain cavity 13 are separated by a third baffle 16.

[0038] Through the combination of the three-layer spiral curtain chamber and the central curtain chamber, a solid conical curtain (with the central curtain chamber fully open) or a multi-layer spiral curtain (with the central curtain chamber partially closed) can be formed according to production requirements, to meet the granulation requirements of different particle sizes of seed crystals. Among them, the central curtain chamber can directly transport the seed crystals to the core area, forming a gradient wrapping with the peripheral spiral curtain, so that the urine spray adheres layer by layer from the outside to the inside, and the particle growth is more sufficient.

[0039] Furthermore, the inlets of the first spiral curtain chamber 10, the second spiral curtain chamber 11 and the third spiral curtain chamber 12 are all connected to the outlets on the pipe wall of the nozzle feed pipe, and the inlet of the central curtain chamber 13 is connected to the outlet at the bottom of the nozzle feed pipe 9. The outlets of the first spiral curtain chamber, the second spiral curtain chamber and the third spiral curtain chamber are all connected to the outlets on the side wall surface of the curtain nozzle, and the outlet of the central curtain chamber is connected to the outlet on the bottom surface of the curtain nozzle.

[0040] The first, second, and third spiral curtain chambers are fed through the side wall outlets of the nozzle feed pipe, while the central curtain chamber is fed through the bottom outlet, ensuring the balance of the seed crystal flow of each layer of the curtain and preventing the accumulation of seed crystals in the central area due to gravity. In addition, since the impact of the seed crystal particles on the pipe wall is mainly concentrated in the side wall outlet area, by optimizing the outlet angle and distribution, the problem of the pipe wall thinning caused by long-term friction can be reduced.

[0041] In this embodiment, the cloth nozzle 4 is fixedly connected to the nozzle feed pipe 9. The nozzle feed pipe 9 is connected to the output shaft of the curtain nozzle motor 1 through a gear transmission mechanism. The curtain nozzle motor is located outside the fluidized bed housing. The seed crystal feed pipe extends into the interior of the nozzle feed pipe, and the diameter of the seed crystal feed pipe is smaller than that of the nozzle feed pipe, and there is no contact between the seed crystal feed pipe and the nozzle feed pipe. Among them, the curtain nozzle motor and the gear transmission mechanism used are both existing structures. It can be understood that the gear transmission mechanism can also be replaced by other transmission mechanisms as long as the rotation of the cloth nozzle can be realized. The curtain nozzle motor drives the cloth nozzle to rotate through the nozzle feed pipe, so that the seed crystal particles are discharged from the spiral curtain chamber under the action of centrifugal force, and at the same time fall to the bottom of the fluidized bed in the form of a spiral curtain under the action of gravity.

[0042] The curtain nozzle motor adopts frequency conversion control, which can dynamically adjust the rotation speed according to the urine spray pressure to ensure that the curtain thickness matches the spray rate, avoiding being too thin (penetrating) or too thick (insufficient wrapping). The nozzle feed pipe and the cloth nozzle are detachably connected. When a certain layer of the spiral chamber is blocked, it can be quickly disassembled and cleaned to reduce the downtime.

[0043] In this embodiment, adjacent two layers of urine nozzles in the multi-layer urine nozzles are misaligned in the vertical direction, and the distance between adjacent two layers of nozzles is greater than the maximum spray angle of the urine nozzles. The adjacent two layers of nozzles are misaligned in the vertical direction, and the distance is greater than the maximum outer arc of the spray angle, ensuring that the urine spray has no overlapping coverage, improving the wrapping uniformity, and expanding the utilization rate of the granulation space; in addition, the misaligned distribution can make the spray cover the entire cross-section of the fluidized bed, reduce the "blind area", and make the particle growth more sufficient. The urine nozzles can be one layer, two layers, three layers or four layers, depending on the device load and equipment size. The vertical distance between the urine nozzles and the outermost conical material curtain is 250 - 300 mm. This distance ensures that the spray cone angle of the urine nozzles can completely cover the outermost side of the material curtain, enabling the seed particles to be fully wrapped. At the same time, the lower limit of the distance, 250 mm, provides a buffer space for the upward airflow in the fluidized bed, avoiding the destruction of the material curtain form by the airflow disturbance.

[0044] In this embodiment, the bottom of the fluidized bed shell has a certain inclination angle, approximately 5° - 10°. The inclination angle enables the particles to naturally slide along the inclined plane towards the discharge port under the action of the fluidizing air, avoiding the problem that the traditional flat-bottom fluidized bed requires an additional vibration or scraper mechanism to push, and reducing the mechanical failure rate. In addition, the inclination angle can ensure that the particles are discharged in time after cooling, avoiding uneven fluidization caused by local accumulation (such as the "dead bed" phenomenon), and is especially suitable for the fluidity requirements of high-humidity urea.

[0045] The working principle of the urea granulator provided in this embodiment is as follows:

[0046] Small-particle urea (seed, with a particle size usually of 1 - 2 mm) enters the cloth nozzle through the nozzle feed pipe, and the feed rate can be adjusted by a frequency conversion motor to ensure stable feeding. The seeds are divided by the multi-layer spiral material curtain cavities (such as the first, second, third layers and the central cavity) in the cloth nozzle to form a solid or multi-layer conical material curtain. The baffle structure ensures the uniform distribution of the seeds, avoiding local accumulation or cavities. The cloth nozzle is driven by a motor to rotate, and the seeds are sprinkled along the spiral cavity under the action of centrifugal force to form a continuous and dense falling material curtain, providing an ideal carrier for urine wrapping.

[0047] The multi-layer urine nozzles on the inner wall of the fluidized bed shell are misaligned. The number of nozzles in each layer is adjusted according to the device load, and the spray angle direction matches the falling trajectory of the material curtain. Urine (molten urea, with a temperature of about 140 °C) is sprayed out from the nozzle under high pressure, vertically penetrates the material curtain, and fully contacts and wraps the seed particles layer by layer. Since the distance between the nozzles is greater than the spray outer arc, the spray cross-interference is avoided, ensuring the wrapping uniformity.

[0048] The seeds gradually grow under the multi-layer urine wrapping to form dense high-strength particles (2.8 - 4.75 mm), and the internal structure of the particles is tight. The particles are discharged through the discharge port at the bottom of the fluidized bed shell.

[0049] 3. Fluidized Bed Cooling and Screening Cycle

[0050] Fluidized bed cooling: The formed particles fall into the fluidized bed with a 5° inclination at the bottom. The cold air (20 - 30°C) sent by the blower rapidly cools and solidifies the particles. At the same time, the air flow blows the fine powder back to the granulation area for re - wrapping.

[0051] Example 2

[0052] In a typical implementation of this example, a urea granulation system is provided. As Figure 3 shown, it further includes a tail gas scrubbing tower 19, an intermediate bucket elevator 25, a screening device, and a return bucket elevator 24; the tail gas scrubbing tower 19 is connected to the air outlet at the top of the fluidized bed shell through an induced draft fan, the inlet of the intermediate bucket elevator 25 is connected to the discharge port at the bottom of the fluidized bed shell, the outlet of the intermediate bucket elevator is connected to the screening device, the particle outlet of the screening device is connected to the particle packaging device, and the return material outlet of the screening device is connected to the nozzle feed pipe at the top of the fluidized bed shell through the return bucket elevator.

[0053] Furthermore, the air inlet at the bottom of the fluidized bed shell is connected to the blower 18, and the urine nozzle on the inner wall surface of the fluidized bed shell is connected to the molten urea supply device through a pipeline.

[0054] The working principle of the urea granulation system provided in this example is as follows:

[0055] The formed particles generated by the urea granulator fall to the bottom of the fluidized bed. The cold air sent by the blower rapidly cools and solidifies the particles. At the same time, the air flow blows the fine powder back to the granulation area for re - wrapping. The cooled particles enter the intermediate bucket elevator through the discharge port and are screened by the first screening device 22 and the second screening device 23. Then, the qualified products (2.8 - 4.75 mm) are transported to the packaging section, and the small particles (<2.8 mm) re - enter the seed material bin through the return bucket elevator for cyclic granulation, with the return material utilization rate >95%.

[0056] The hot air containing urea dust generated during the granulation process is drawn into the tail gas scrubbing tower by the induced draft fan 20. The urine is recovered through water washing, and after the concentration of the washing liquid meets the standard, it is pumped back to the evaporation system for reuse. The tail gas treatment system can reduce the dust emission to <10 mg / m 3 , meeting the environmental protection requirements and reducing raw material waste at the same time.

[0057] Example 3

[0058] In a typical implementation of the present invention, a urea granulation process is provided, including:

[0059] The seed granular urea forms a multi-layer spiral conical material curtain under the action of the cloth spraying nozzle. During the falling process of the granular urea, it forms large particles under the wrapping of the urine sprayed by the multi-layer urine spraying nozzles and falls to the bottom of the fluidized bed. After being cooled by the incoming air at the bottom of the fluidized bed, it is discharged through the discharge port.

[0060] The discharged materials are lifted by the intermediate bucket elevator and enter the screening device. After screening, the finished large particles enter the finished product packaging system through the conveyor belt; the small particles after being screened by the screening device are lifted by the return bucket elevator and enter the seed material bin, and enter the cloth spraying nozzle together with the fresh seeds, achieving continuous production.

[0061] Furthermore, the hot air and dust of the granulator are sent into the tail gas scrubbing tower by the induced draft fan for scrubbing. When the urine concentration meets the requirements, it is pumped back to the evaporation system of the urea plant through the scrubbing pump.

[0062] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A urea granulator based on a spiral cloth spraying nozzle, characterized in that, It includes a fluidized bed shell, at the top of which a cloth spraying nozzle is arranged. The cloth spraying nozzle is communicated with a nozzle feed pipe. On the inner wall surface of the fluidized bed shell, multiple layers of urine nozzles are arranged successively from top to bottom. At the bottom of the fluidized bed, an air inlet and a discharge outlet are provided; inside the cloth spraying nozzle, multiple layers of spiral material curtain cavities are arranged successively from top to bottom. The spiral material curtain cavities are communicated with the nozzle feed pipe.

2. The urea granulator based on the spiral cloth nozzle according to claim 1, characterized in that Adjacent spiral material curtain cavities are separated by baffles. The baffles are inclined. The top of the baffle extends into the nozzle feed pipe, and the lengths of multiple baffles extending into the nozzle feed pipe increase successively from top to bottom.

3. The urea granulator based on the spiral cloth spraying nozzle according to claim 2, characterized in that, The spiral material curtain cavities include a first spiral material curtain cavity, a second spiral material curtain cavity, a third spiral material curtain cavity and a central material curtain cavity. The first spiral material curtain cavity and the second spiral material curtain cavity are separated by a first baffle. The second spiral material curtain cavity and the third spiral material curtain cavity are separated by a second baffle. The third spiral material curtain cavity and the central material curtain cavity are separated by a third baffle.

4. The urea granulator based on the spiral cloth spray head according to claim 3, characterized in that, The inlets of the first spiral material curtain cavity, the second spiral material curtain cavity and the third spiral material curtain cavity are all communicated with the outlets on the pipe wall of the nozzle feed pipe. The inlet of the central material curtain cavity is communicated with the outlet at the bottom of the nozzle feed pipe.

5. The urea granulator based on a spiral cloth spray head as claimed in claim 1, wherein, The cloth spraying nozzle is fixedly connected with the nozzle feed pipe. The nozzle feed pipe is connected with the output shaft of a material curtain spraying nozzle motor through a gear transmission mechanism. The material curtain spraying nozzle motor is located outside the fluidized bed shell, and the seed feed pipe extends into the interior of the nozzle feed pipe.

6. The urea granulator based on a spiral cloth spray head according to claim 1, wherein, Between adjacent two layers of urine nozzles in the multiple layers of urine nozzles, they are distributed with a vertical offset. The distance between adjacent two layers of nozzles is greater than the maximum spraying angle of the urine nozzles.

7. A urea granulation system, comprising the urea granulator according to any one of claims 1-6, characterized in that, It also includes a tail gas scrubbing tower, an intermediate bucket elevator, a screening device and a return bucket elevator; the tail gas scrubbing tower is connected with the air outlet at the top of the fluidized bed shell through a draft fan. The inlet of the intermediate bucket elevator is connected with the discharge outlet at the bottom of the fluidized bed shell. The outlet of the intermediate bucket elevator is connected with the screening device. The particle outlet of the screening device is connected with a particle packaging device. The return material outlet of the screening device is connected with the nozzle feed pipe at the top of the fluidized bed shell through the return bucket elevator.

8. The urea granulation system according to claim 7, characterized in that, The air inlet at the bottom of the fluidized bed shell is connected with a blower. The urine nozzles on the inner wall surface of the fluidized bed shell are connected with a molten urea supply device through pipelines.

9. A urea granulation process, which uses the urea granulation system as described in claim 8, is characterized in that, It includes: The seed granular urea forms multiple layers of spiral conical material curtains under the action of the cloth spraying nozzle. During the falling process of the granular urea, it forms large particles under the wrapping of the urine sprayed by the multiple layers of urine nozzles and falls to the bottom of the fluidized bed. After being cooled by the air inlet at the bottom of the fluidized bed, it is discharged through the discharge outlet. The discharged materials are lifted by the intermediate bucket elevator and enter the screening device for screening. The finished large particles enter the finished product packaging system through a conveyor belt; the small particles screened by the screening device are lifted by the return bucket elevator and enter the seed material bin and enter the cloth spraying nozzle together with the fresh seeds, achieving continuous production.

10. The urea granulation process according to claim 9, wherein, The hot air and dust of the granulator are sent into the tail gas scrubbing tower for washing by the draft fan. When the urine concentration reaches the requirement, it is pumped back to the evaporation system of the urea plant through a washing pump.

Images