Large granular urea drum granulation method

Abstract

The invention discloses a large granular urea drum granulation method which is implemented by adopting integrated drum granulation equipment, the equipment comprises an integrated drum cylinder, a granulation cabin and a cooling cabin are sequentially arranged in the integrated drum cylinder along the material advancing direction, and a material curtain control structure is arranged between the two cabins. The method comprises the following steps: adding seed crystals into a granulation cabin to form a material curtain; spraying molten urine and introducing granulation air with controllable temperature, so that the urine is crystallized and grows on the surface of the seed crystal; the granulated urea enters the cooling cabin through the material curtain control structure; and cooling air with controllable temperature is introduced, a micro-negative pressure environment is kept for cooling, and finally the temperature of the urea particles is reduced to 60-75 DEG C. Through the integrated granulation-cooling process, the problems of particle adhesion and deformation caused by high discharge temperature of a traditional rotary drum are solved, the roundness and the yield of products are improved, meanwhile, dust dissipation is reduced through uniform air distribution, and the device has the advantages of being low in energy consumption, low in investment and small in occupied space.

Description

Technical Field

[0001] This invention relates to the field of large-particle urea production, specifically to a method for rotary drum granulation of large-particle urea. Background Technology

[0002] The main production processes for large-particle urea currently include atomized fluidized bed, jet fluidized bed, and dual-drum fluidized bed processes. While atomized and jet fluidized beds can achieve efficient granulation, they suffer from high technology import costs, large equipment investments, high energy consumption, and poor particle sphericity, limiting market acceptance. The dual-drum fluidized bed process improves particle sphericity and energy consumption, but its granulation drum discharge temperature is typically above 85℃, even exceeding 95℃. High-temperature particles are prone to adhesion and deformation in subsequent processes such as bucket elevator, screening, and crushing, severely impacting yield, product quality, and particle appearance. Furthermore, uneven air distribution in existing drum processes leads to severe dust emission, increasing environmental pollution and subsequent treatment costs.

[0003] Therefore, there is an urgent need for a large-particle urea production process that can achieve efficient granulation, effectively control the discharge temperature, and reduce dust emissions. Summary of the Invention

[0004] The present invention aims to provide a rotary drum granulation method for large-particle urea to solve the problems of high temperature of urea particles in the discharge of the granulation rotary drum in the prior art, which easily causes particle adhesion and deformation during bucket elevator, screening and crushing processes, affecting the yield, quality and roundness of finished products.

[0005] The basic concept of the technical solution adopted in this invention is as follows: A method for rotary drum granulation of large-particle urea, implemented using an integrated rotary drum granulation device, the device comprising an integrated rotary drum body with a granulation chamber and a cooling chamber arranged sequentially along the material travel direction inside, and a material curtain control structure provided between the granulation chamber and the cooling chamber; the method includes the following steps: S1: Seed crystals are continuously added to the granulation chamber, forming a material curtain under the rotation of the integrated rotary drum. S2: Molten urine is sprayed into the granulation chamber and temperature-controlled granulation air is introduced into it, so that the urine is wrapped, crystallized and grown into large urea particles on the surface of the seed crystals. S3: After granulation, the large urea particles are formed into a material curtain with controllable thickness through the material curtain control structure and enter the cooling chamber; S4: Temperature-controlled cooling air is introduced into the cooling chamber to cool the large urea particles, and at the same time, a slightly negative pressure environment is formed and maintained in the cooling chamber by exhaust gas outlet. S5: Control the cooling process parameters to reduce the temperature of the urea particles discharged from the cooling chamber to 60-75°C.

[0006] As an example, the material curtain control structure includes an adjustable urea guide plate and a flow control plate; in step S3, the thickness of the material curtain and the flow state of the urea particles are controlled by adjusting the angle between the urea guide plate and the horizontal direction to 35° to 55° and the angle between the flow control plate and the vertical direction to 5° to 15°.

[0007] As an example, in step S2, the granulation air is uniformly distributed by a perforated air distribution plate installed on the granulation air pipeline before being introduced into the granulation chamber. The perforated plate has an opening ratio of 4.5% to 5.5%, and the channels are set at an inclination of 30° to 45° in the opposite direction of material movement.

[0008] As an example, in step S2, the temperature of the granulation air is controlled at 135℃±3℃ by an independent temperature control system; in step S4, the temperature of the cooling air is controlled at 25℃~40℃.

[0009] As an example, in step S4, the gauge pressure of the micro-negative pressure environment is -100 Pa to -500 Pa.

[0010] As an example, the rotational speed of the integrated drum body is adjusted to 5-10 rpm, and the inclination angle of the urea guide plate and the flow control plate are adjusted in coordination to control the residence time and processing capacity of urea particles in the granulation chamber and the cooling chamber; wherein, increasing the angle between the flow control plate and the vertical direction is used to increase the thickness of the material curtain to produce urea particles with a larger particle size.

[0011] As an example, in step S4, the cooling air is uniformly distributed by a perforated air distribution plate before being introduced into the cooling chamber.

[0012] As an example, the large urea particles produced by the method have a particle size of 2 to 8 mm and a particle crushing strength of not less than 30 N.

[0013] Compared with the prior art, the present invention has the following advantages: 1. The large-particle urea rotary drum granulation method of the present invention is an integrated granulation-cooling process, which integrates granulation and cooling in the same rotary drum and directly controls the discharge temperature at 60-75°C. This fundamentally avoids the adhesion and deformation of high-temperature particles in subsequent processes, and significantly improves the yield, product quality and particle roundness.

[0014] 2. The present invention further achieves uniform distribution of granulation air and cooling air through a perforated air distribution plate, improves airflow uniformity, reduces local overheating or overcooling, reduces dust generation and dispersion, and reduces the burden of exhaust gas treatment.

[0015] 3. The method of the present invention does not require additional configuration of fluidized bed heat exchangers or plate cooling equipment, which reduces equipment investment and floor space. At the same time, through precise temperature control and micro negative pressure operation, the system energy consumption is reduced.

[0016] 4. The process of this invention is flexible and controllable. By adjusting parameters such as drum speed, angle between guide plate and flow control plate, air temperature and air pressure, flexible production of different particle sizes and capacities can be achieved to meet diverse market demands.

[0017] 5. The method of the present invention is environmentally friendly. The micro-negative pressure operation effectively guides dust into the exhaust gas treatment system, reduces on-site dust pollution, and improves the operating environment.

[0018] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention may be realized and obtained by means of the structures particularly pointed out in the description, claims, and drawings. Attached Figure Description

[0019] The accompanying drawings are provided to further understand the technical solutions of the present invention and constitute a part of the specification. They are used together with the embodiments of this application to explain the technical solutions of the present invention and do not constitute a limitation on the technical solutions of the present invention.

[0020] Figure 1 This is a schematic diagram of the overall structure of the large-particle urea rotary drum granulation equipment described in this invention.

[0021] Figure 2 yes Figure 1 AA cross-section view.

[0022] Figure 3 yes Figure 1 BB cross-section.

[0023] Figure 4 yes Figure 1 CC cross-section view.

[0024] Figure 5 This is a schematic diagram of a perforated plate.

[0025] Figure 6 This is a partial structural diagram of the integrated drum body and the support roller assembly.

[0026] Marked in the image: 1-Integrated rotary drum body; 2-Pelletizing chamber; 3-Cooling chamber; 4-Urea guide plate; 5-Flow control plate; 6-Urea inlet; 7-Pelletizing air inlet; 7.1-Pelletizing air pipe; 8-Pelletizing air nozzle; 9-Lifting plate; 10-Exhaust gas outlet; 11-Pellet outlet; 12-Urea nozzle; 13-Variable frequency motor drive mechanism; 14-Transmission mechanism; 15-Support mechanism; 16-Pelletizing air support; 17-Cooling air inlet; 17.1-Cooling air pipe; 18-Cooling air support; 19-Seed inlet; 20-Cooling air nozzle; 21-Drum front enclosure; 22-Cooling chamber end enclosure; 23-Perforated air distribution plate; 23.1-Channel; 23.2-Plate body; 24-Urea pipe support; 25-Roller assembly; 25.1-Roller assembly connecting rod; 25.2-Roller assembly base; 25.3-Roller; 25.4-Roller outer support; 25.5-Rolling ring. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, 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, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the described embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0028] This invention relates to a large-particle urea rotary drum granulation device integrating urea granulation, cooling, and temperature control. The invention divides the drum into a granulation chamber 2 (high-temperature zone) and a cooling chamber 3 (low-temperature zone). Particle forming and cooling are completed within the integrated drum body 1, preventing the high-temperature urea particles from sticking or deforming during secondary transfer and subsequent processes (such as bucket elevators, screening, and crushing). A perforated air distribution plate 23 is simultaneously installed in both the granulation chamber 2 and the cooling chamber 3. This ensures uniform material distribution and air supply during the granulation process, reducing excessive local seed crystal flow and air volume, which could lead to uneven spraying and excessive urea dust. Furthermore, it ensures uniform cooling of the granulated urea particles in the cooling chamber 3.

[0029] Example 1 Provides a rotary drum granulation device for large-particle urea, with reference to Figure 1-6 It includes: An integrated rotary drum body 1 has a granulation chamber 2 and a cooling chamber 3 arranged sequentially inside along the material travel direction; a granulation system is set in the granulation chamber 2, including a seed inlet 19, a urine spray device (specifically a urine nozzle 12), and a granulation air distribution device; a cooling system is set in the cooling chamber 3, including a cooling air distribution device; and a drive and support mechanism for driving and supporting the rotation of the integrated rotary drum body 1; wherein, both the granulation air distribution device and the cooling air distribution device include a perforated air distribution plate 23 set in the air supply path, and the tail end of the cooling chamber 3 is provided with an exhaust gas outlet 10 connected to the induced draft fan, so as to form a micro negative pressure zone (the pressure value of the micro negative pressure zone is -100 to -500 Pa (gauge pressure)) in the cooling chamber 3.

[0030] The core component is an integrated rotary drum body 1, which is made of carbon steel rolled and welded. Its interior is divided into two functional compartments along its axial direction (i.e. the material travel direction): the front granulation compartment 2 and the rear cooling compartment 3. The core material curtain control structure controls the granulation particle size to meet production requirements (e.g., control the particle size to 2-4mm or 4-8mm).

[0031] As an example of optimization, the length ratio of the granulation chamber 2 to the cooling chamber 3 is 1:(0.8-1.2) to ensure that the granules have sufficient cooling time.

[0032] Taking a capacity of 100,000 tons / year / set as an example, the granulation chamber 2 is approximately φ3600mm×11000mm, and the cooling chamber 3 is approximately φ3600mm×9500mm.

[0033] As an example, the material curtain control structure specifically includes: The urea guide plate 4 is inclinedly installed inside the integrated drum body 1, with its high end located on one side of the granulation chamber 2, and is used to receive and guide the urea particles falling from the lifting plate 9. The flow control plate 5 is located below the lower outlet of the urea guide plate 4 and is inclined at an acute angle to the vertical direction to form a urea granule curtain with controllable thickness.

[0034] The lifting plates 9 are located on the inner wall of the integrated drum body 1. They are used to lift and sprinkle material as the drum rotates, so that the falling urea particles are received and guided by the urea guide plate 4. When the integrated drum body 1 rotates, the lifting plates 9 continuously lift the material from the bottom to the top, and then, under the action of gravity, evenly disperse the material on the urea guide plate 4. The specific number of lifting plates 9 is calculated based on the inner diameter of the integrated drum body 1 and product requirements.

[0035] As a more concrete example, the urea guide plate 4 is a long strip of 304 stainless steel plate. Its high end is hinged to two symmetrical supports welded to the inner wall of the integrated drum body 1 via a rotating shaft. One end of the rotating shaft extends to the outside of the drum body and is equipped with a locking nut with a handle. By loosening the nut, the tilt angle of the urea guide plate 4 can be adjusted by manually rotating the handle, with an adjustment range of 35°-55°. For example, when fixed at 45°, the lower end of the guide plate extends downward, leaving a gap of approximately 100mm between it and the inner wall of the drum body.

[0036] As a more concrete example, the flow control plate 5 is a narrow strip plate, mounted on a dedicated support directly below the lower end of the urea guide plate 4 via another rotating shaft. The support has multiple slots for adjusting angle settings (e.g., slots corresponding to angles of 5°, 7.5°, 10°, 12.5°, and 15° with respect to the vertical). The end of the rotating shaft of the flow control plate 5 can be inserted into different slots to form urea granules with controllable thickness. For example, a 10° slot can be selected for insertion, and a locating pin can be used to secure it through pin holes on the support and rotating shaft.

[0037] The aforementioned urea guide plate 4 and flow control plate 5, together with the inner wall of the cylinder, form a narrow channel whose cross-section first contracts (at guide plate 4) and then changes direction (at flow control plate 5). Urea particles can continuously slide down within this channel and form a material curtain with controllable width.

[0038] As an example, the granulation system set in the granulation chamber 2 includes: a seed inlet 19 and a urine spray nozzle 12 (which can be set in a conventional manner) and a granulation air distribution device.

[0039] As an example, the granulation air distribution device includes a granulation air pipe 7.1 arranged along the axis of the integrated drum body 1, which is fixed by a granulation air support 16. Multiple downward-discharging granulation air nozzles 8 are welded to the pipe. For better results, a perforated air distribution plate 23 can be further installed parallel to each nozzle at approximately 150 mm below its outlet. This perforated air distribution plate 23 is fixed to the inner wall of the integrated drum body 1 by an angle steel frame.

[0040] Specifically, such as Figure 5 As shown, in one embodiment, the plate body 23.2 of the perforated air distribution plate 23 is made of 304L stainless steel plate, and the diameter of the holes 23.1 opened on it is 2mm, with a center-to-center distance of 8mm; the perforation rate of the perforated air distribution plate 23 is 4.5%-5.5%, and the holes are opened at an angle of 30°-45° in the opposite direction of material falling.

[0041] As an example, the top of the granulation chamber 2 is equipped with a seed inlet 19 and multiple urine nozzles 12. A granulation air pipe 7.1 extends axially along the integral drum body 1 and is located on one side there. The downward-facing granulation air nozzles 8 are evenly installed on the pipe. A stainless steel perforated plate is covered below the granulation air nozzles 8 as an air distribution perforated plate 23. Granulation air enters through the inlet 7, and the temperature is stabilized at 135°C by the steam control system.

[0042] As an example, the cooling system installed in the cooling chamber 3 includes a cooling air distribution device, similar in structure to the granulation chamber 2, consisting of multiple parallel cooling air pipes 17.1 (fixed by cooling air supports 18) and corresponding cooling air nozzles 20 and perforated distribution plates 23. A regulating valve is provided at the cooling air inlet 17. The exhaust outlet 10 on the end cover 22 of the cooling chamber is connected to a centrifugal induced draft fan. By adjusting the speed of the centrifugal induced draft fan, the pressure near the exhaust outlet 10 of the cooling chamber 3 is controlled at -100 Pa (gauge pressure), forming a stable micro-negative pressure environment.

[0043] The integrated drum body 1 has a urea guide plate 4 and a flow control plate 5 fixed inside by a welded support frame, and a lifter plate 9 is also installed on the inner wall. The variable frequency motor drive mechanism 13 drives the integrated drum body 1 to rotate through the transmission mechanism 14 in a gear meshing manner. When rotating, the lifter plate 9 carries the urea particles to the upper space, and the urea particles fall freely onto the urea guide plate 4 under the action of gravity.

[0044] The urea guide plate 4 is equipped with a rotating shaft structure with a locking nut at its connecting shaft end. This rotating shaft structure is movably connected to the bracket on the inner wall of the integrated drum body 1. The urea guide plate 4 can rotate around the rotating shaft to adjust its angle with the horizontal direction. During adjustment, first loosen the locking nut, manually rotate the guide plate to the target angle between 35-55°, then tighten the nut to fix the rotating shaft. The angle is locked by the friction between the nut and the bracket, preventing the guide plate from shifting due to vibration during equipment operation. When the urea is collected and falls, it passes through a flow control plate 5 with an adjustable angle of 5-15° to the vertical direction. The mounting bracket of the flow control plate 5 has multiple slots (e.g., 2.5° or 5°) according to production needs. After the rotating shaft of the flow control plate 5 is inserted into the corresponding slot, a positioning pin is inserted to fix it. This allows for adjustment to form urea granule curtains of different thicknesses according to production capacity requirements. When producing smaller urea granules, the angle between the flow control plate 5 and the vertical direction tends to be 5°; conversely, when producing larger urea granules, it tends to be 15°.

[0045] In one manner, the urea guide plate 4 is inclinedly arranged inside the integrated drum body 1, and a rotating shaft structure with a locking nut is added to the end of its connecting shaft. Its high end is located on one side of the granulation chamber 2, which is used to receive and guide the urea particles falling from the lifting plate 9.

[0046] In one embodiment, the flow control plate 5 is positioned below the lower outlet of the urea guide plate 4, and is inclined at an acute angle to the vertical direction. The flow control plate 5 adjusts its tilt angle through a slot. When the machine stops, the rotating shaft of the control plate is inserted into the corresponding gear slot and then fixed by a positioning pin, which is used to form a urea granule curtain with controllable thickness.

[0047] The top of the cooling chamber 3 is equipped with multiple cooling air pipes 17.1, and cooling air nozzles 20 are installed at the bottom of the branch pipes, which are also covered with perforated air distribution plates 23. Cooling air enters through inlet 17 and the temperature is controlled at 40℃. The end of the cooling chamber 3 is equipped with an exhaust outlet 10, which is connected to an induced draft fan to maintain a slight negative pressure (e.g., about -100 Pa) near the exhaust outlet 10 of the cooling chamber 3.

[0048] To facilitate the rotation of the integrated drum body 1, the drive and support mechanism for driving and supporting the rotation of the integrated drum body 1 includes a gear transmission group, at least two sets of roller groups 25, and a support mechanism 15. The gear transmission group meshes with a gear ring disposed on the outer periphery of the integrated drum body 1 and is driven by a variable frequency motor drive mechanism 13; the roller groups 25 are symmetrically supported below the rolling ring 25.5 of the integrated drum body 1. An elastic damping pad with a thickness of 20mm is provided between the bearing seat of the roller 25.3 in the roller group 25 and the outer support 25.4 of the roller. This design can absorb the impact of materials and the vibration generated by the rotation of the integrated drum body 1, avoid the load being directly transmitted to the integrated drum body 1, and meet the functional requirements of stable support for heavy structures, allowing free rotation, bearing working loads, facilitating maintenance, compensating for installation errors and thermal expansion.

[0049] In one embodiment, the variable frequency speed regulation range of the variable frequency motor drive mechanism 13 corresponds to the rotational speed of the integrated drum body 1, which is 5-10 rpm.

[0050] In addition, by adjusting the speed of the variable frequency motor and the angle between the urea guide plate 4 and the flow control plate 5, the material residence time, processing capacity and product particle size can be flexibly adjusted to meet different production needs.

[0051] The large-particle urea rotary drum granulator is equipped with an independent temperature control system. Through temperature sensors, pressure gauges, flow meters, and pneumatic regulating valves installed on the granulation air pipeline and the cooling air pipeline, independent closed-loop control of the two air temperatures can be achieved. Specific settings can utilize existing technology. For example, on the pipeline before the granulation air inlet 7, a first steam heat exchanger, a first temperature sensor (PT100), and a first pneumatic regulating valve are installed sequentially. The granulation air temperature is set to 135℃. On the pipeline before the cooling air inlet 17, a second hot water heat exchanger (for winter use), a second temperature sensor, and a second pneumatic regulating valve are installed sequentially. The cooling air temperature is set to 25℃. The independent temperature control system includes a PLC controller. The first and second temperature sensors transmit the detected air temperature signals to the PLC. The PLC presets the target granulation air temperature (e.g., 135℃) and the target cooling air temperature (e.g., 25℃ or 40℃). The PLC compares the measured value with the target value using a built-in PID algorithm, and outputs a 4-20mA control signal to the first and second pneumatic regulating valves to regulate the flow rate of steam or hot water entering the heat exchanger, thereby achieving closed-loop stable control of air temperature.

[0052] The main process for producing large-particle urea using the large-particle urea rotary drum granulation equipment described in this invention is as follows: After the equipment is started, the integrated drum body 1 rotates at a preset speed (e.g., 5 rpm).

[0053] The seed crystals are added from the seed crystal inlet 19, lifted and scattered by the lifting plate 9 to form a material curtain.

[0054] Molten urine is atomized and sprayed through urine nozzle 12, and granulation air (e.g., 135℃) evenly penetrates the material curtain to complete particle encapsulation and initial solidification.

[0055] Then, the particles move with the material flow to the material curtain control structure, are gathered by the guide plate 4, and smoothly enter the cooling chamber 3 through the material curtain (e.g., at a 10° inclination angle) formed by the flow control plate 5.

[0056] Inside the cooling chamber 3, 40°C cooling air is evenly blown onto the particle layer for efficient heat exchange. At the same time, a slight negative pressure (e.g., -100Pa) forms a directional airflow, guiding the dust to the exhaust gas treatment system.

[0057] Finally, the temperature of the urea granules is reduced to about 68°C and discharged from granule outlet 11 to enter the subsequent packaging process.

[0058] The following is a detailed description of the working process of the large-particle urea rotary drum granulation equipment: The seed crystals enter the granulation chamber 2 through the seed inlet 19 and are uniformly coated layer by layer by small droplets formed by atomization through the urea nozzle 12. Preheated granulation air passes sequentially through the granulation air inlet 7 and the granulation air nozzle 8, and is then uniformly sprayed into the granulation chamber 2 through the perforated air distribution plate 23. The coated particles are repeatedly circulated by a control system consisting of the urea guide plate 4 and the flow control plate 5 to increase their size. Cooling air is uniformly distributed through the perforated air distribution plate 23 of the cooling air distribution device to cool the large particles. The exhaust gas generated during the cooling process is discharged through the exhaust gas outlet 10, and the cooled urea particles are discharged from the particle outlet 11 of the integrated drum body 1.

[0059] In this process, granulation air and cooling air exchange heat through a variable frequency fan and heat exchanger at the front end before entering the integrated rotary drum 1. Pressure gauges, flow meters, and thermometers are installed on the air pipeline to adjust the air flow rate according to production needs. The outlet temperatures of the granulation air and cooling air are controlled by a matching pneumatic control valve. For example, the inlet temperature of the granulation air is controlled at 135℃, the cooling air heat exchanger is only activated when the environment is humid and cold (recommended value ≤15℃), and the temperature entering the integrated rotary drum 1 is controlled at 25℃ to prevent problems such as decreased strength and increased dust production caused by excessive cooling of the urea. Due to the heat of crystallization and external heat exchange during granulation, the length of the cooling chamber 3 is appropriately set to ensure sufficient cooling residence time for large urea particles.

[0060] Urea granules are gradually introduced into the cooling chamber 3. Cooling air is introduced through the cooling air inlet 17 and then evenly sprayed onto the urea granules by the cooling air nozzle 20 through the perforated air distribution plate 23, reducing the temperature to 60-75°C and eliminating the risk of adhesion. At the same time, an exhaust fan is installed at the rear end of the drum to draw a slight negative pressure at the exhaust outlet 10 of the drum cooling chamber 3 (creating a pressure difference of 5-10 kPa with the bottom of the drum and the granulation chamber 2), forming a gas phase flow driving force to carry the dust and exhaust gas generated during granulation and cooling into the exhaust outlet 10 for subsequent processing.

[0061] Example 2 A method for granulating large-particle urea using the equipment described in Embodiment 1 above is provided, comprising the following steps: S1: Seed crystals are continuously added to the granulation chamber 2, forming a material curtain under the rotation of the integrated drum body 1; S2: Molten urea and temperature-controlled granulation air are sprayed into the granulation chamber 2, causing the urea to coat, crystallize, and grow on the surface of the seed crystals; S3: Granulated urea particles enter the cooling chamber 3 through the material curtain control structure; S4: Temperature-controlled cooling air is introduced into the cooling chamber 3 to cool the urea particles, while exhaust gas outlet 10 is used to maintain a slight negative pressure in the cooling chamber 3; S5: Cooling process parameters are controlled to reduce the temperature of the urea particles discharged from the cooling chamber 3 to 60~75℃.

[0062] As an example, in step S2, the temperature of the granulation air is controlled at 135℃±3℃; in step S4, the temperature of the cooling air is controlled at 40℃; and the pressure value of the micro negative pressure is -100~-500 Pa (gauge pressure).

[0063] In practice, the residence time of urea granules and the thickness of the material curtain in the granulation chamber 2 and cooling chamber 3 are controlled by adjusting the rotation speed of the integrated drum body 1 and the tilt angles of the urea guide plate 4 and the flow control plate 5. Adjusting the rotation speed of the integrated drum body 1 to 5 rpm, the tilt angle of the urea guide plate 4 to 50°, and the tilt angle of the flow control plate 5 to 5° increases the material curtain thickness and throughput.

[0064] Meanwhile, the granulation air temperature was increased to 138℃, and the cooling air volume was increased by 20%. Through adjustment, the final discharge temperature was stabilized at around 68℃, the production capacity reached 105%, the average particle size was 2.42mm, the crushing strength was about 32N, and the product quality remained stable.

[0065] Example 3 The operation steps of Example 3 are the same as those of Example 2, only the operation parameters are changed.

[0066] As an example, in step S2, the temperature of the granulation air is controlled at 135°C; in step S4, the temperature of the cooling air is controlled at 25°C; and the pressure value of the micro-negative pressure is -100 to -500 Pa (gauge pressure).

[0067] In practice, the residence time of urea granules and the thickness of the material curtain in the granulation chamber 2 and cooling chamber 3 are controlled by adjusting the rotation speed of the integrated drum body 1 and the tilt angles of the urea guide plate 4 and the flow control plate 5. The rotation speed of the integrated drum body 1 is adjusted to 5 rpm, the tilt angle of the urea guide plate 4 is adjusted to 35°, and the tilt angle of the flow control plate 5 is adjusted to 10° to reduce the thickness of the material curtain and the throughput.

[0068] Meanwhile, the granulation air temperature is precisely controlled at 135℃, and the cooling air volume operates at 100% load. Through adjustment, the final discharge temperature is stabilized at around 72℃, the production capacity reaches 85%, the average particle size is 4.68mm, the crushing strength is about 37N, and the product quality remains stable.

[0069] While the embodiments disclosed in this invention are as described above, the content is merely for the purpose of facilitating understanding of the invention and is not intended to limit the invention. Any person skilled in the art to which this invention pertains may make any modifications and changes to the form and details of the implementation without departing from the spirit and scope disclosed herein; however, the scope of patent protection of this invention shall still be determined by the scope defined in the appended claims.

Claims

1. A method for rotary drum granulation of large-particle urea, characterized in that, The method employs an integrated rotary drum granulation device, which includes an integrated rotary drum body (1) with a granulation chamber (2) and a cooling chamber (3) arranged sequentially along the material travel direction inside. A material curtain control structure is provided between the granulation chamber (2) and the cooling chamber (3). The method includes the following steps: S1: The seed crystals are continuously added to the granulation chamber (2), and a material curtain is formed under the rotation of the integrated drum body (1); S2: Molten urine is sprayed into the granulation chamber (2), and temperature-controlled granulation air is introduced into it, so that the urine is wrapped, crystallized and grown into large urea particles on the surface of the seed crystals. S3: After granulation, the large granulated urea particles are formed into a material curtain with controllable thickness through the material curtain control structure and enter the cooling chamber (3). S4: Temperature-controlled cooling air is introduced into the cooling chamber (3) to cool the large urea particles, and at the same time, a slightly negative pressure environment is formed and maintained in the cooling chamber (3) by exhausting air through the exhaust outlet. S5: Control the cooling process parameters to reduce the temperature of the urea particles discharged from the cooling chamber (3) to 60-75°C.

2. The method for rotary drum granulation of large-particle urea according to claim 1, characterized in that, The material curtain control structure includes an adjustable tilt angle urea guide plate (4) and a flow control plate (5); in step S3, the thickness of the material curtain and the flow state of the urea particles are controlled by adjusting the angle between the urea guide plate (4) and the horizontal direction to 35° to 55° and adjusting the angle between the flow control plate (5) and the vertical direction to 5° to 15°.

3. The method for rotary drum granulation of large-particle urea according to claim 1 or 2, characterized in that, In step S2, before the granulation air is introduced into the granulation chamber (2), it is first uniformly distributed by the perforated air distribution plate (23) set on the granulation air pipeline; The perforated plate (23) has an opening ratio of 4.5% to 5.5%, and the channels are set at an inclination of 30° to 45° in the opposite direction of material movement.

4. The method for rotary drum granulation of large-particle urea according to claim 1, characterized in that, In step S2, the temperature of the granulation air is controlled at 135℃±3℃ by an independent temperature control system; in step S4, the temperature of the cooling air is controlled at 25℃~40℃.

5. The method for rotary drum granulation of large-particle urea according to claim 1, characterized in that, In step S4, the gauge pressure of the micro-negative pressure environment is -100 Pa to -500 Pa.

6. The method for rotary drum granulation of large-particle urea according to claim 1, characterized in that, The rotational speed of the integrated drum body (1) is adjusted to 5-10 rpm, and the inclination angle of the urea guide plate (4) and the flow control plate (5) is adjusted in coordination to control the residence time and processing capacity of urea particles in the granulation chamber (2) and the cooling chamber (3); wherein, the angle between the flow control plate (5) and the vertical direction is increased to increase the thickness of the material curtain to produce urea particles with a larger particle size.

7. The method for rotary drum granulation of large-particle urea according to claim 1, characterized in that, In step S4, the cooling air is evenly distributed through the perforated air distribution plate (23) before entering the cooling chamber (3).

8. The method for rotary drum granulation of large-particle urea according to claim 1, characterized in that, The large-particle urea produced by the method has a particle size of 2-8 mm and a particle crushing strength of not less than 30 N.

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