Closed low-tower granulation process device

Abstract

The invention relates to the technical field of granulation, in particular to a closed low-tower granulation process device. The system comprises a granulation tower, a granulator, a forced ventilation system, a circulating air system, a tail gas treatment system and a temperature regulation and control module, a tower body of the granulation tower is made of a metal material, the height of the tower body is 35-45m, and the tower body is divided into a working cavity and a cooling cavity by a division plate; the forced ventilation system forcibly forms upflow in the cooling cavity; the circulating air system guides part of tail gas of the working cavity back to the tower bottom; the tail gas treatment system treats gas in the working cavity and partially guides the gas back to the tower bottom; the temperature regulation and control module regulates the temperature in the tower, and a plurality of regulating valves, sensors and a controller are arranged in the system for matched regulation. The technical effects that the temperature, the gas flow and the air inlet proportion in the granulation tower can be effectively controlled, tail gas recycling and treatment are achieved, and meanwhile it is guaranteed that the granulation process is efficiently and stably carried out through the structures such as the special air distributor and the scraping plate are achieved.

Description

Technical Field

[0001] This application relates to the technical field of granulation, and in particular to a closed-type low-tower granulation process apparatus. Background Technology

[0002] Granulation technology for ammonium nitrate and compound fertilizers plays a vital role in the chemical production field. With the continuous development of the chemical industry, the optimization and innovation of granulation processes are crucial for improving production efficiency, reducing costs, and enhancing product quality. Efficient granulation processes ensure the uniformity and stability of ammonium nitrate and compound fertilizer particles, meeting the diverse needs of agricultural production. Furthermore, a rational granulation process helps reduce resource waste and environmental pollution during production.

[0003] In the production of ammonium nitrate and compound fertilizers, the conventional method to solve the granulation problem has been high-tower granulation. Granulation towers are generally quite tall, and the tower body is usually made of concrete. The granulation process relies on open natural ventilation, where atmospheric air naturally enters the tower and comes into contact with the slurry droplets coming down from the granulator at the top, and the exhaust gas is directly discharged at the top. Cooling during granulation mainly relies on natural ventilation, and the product at the bottom of the tower is discharged by gravity. This granulation method can, to a certain extent, complete the granulation production of ammonium nitrate and compound fertilizers.

[0004] However, existing high-tower granulation technology has significant drawbacks. The excessive height of the tower leads to high investment and operating costs; open natural ventilation makes it difficult to collect and treat dust in the exhaust gas at the top of the tower; moreover, granulation cooling relies on natural ventilation, and with seasonal changes, the temperature of the product particles at the bottom of the tower is difficult to control, directly affecting product quality. Summary of the Invention

[0005] In order to reduce investment costs and achieve exhaust gas dust recovery, this application provides a closed-loop low-tower granulation process device.

[0006] The closed-loop low-tower granulation process device provided in this application adopts the following technical solution: A closed-loop low-tower granulation process device includes a granulation tower, a granulator, a forced ventilation system, a circulating air system, an exhaust gas treatment system, and a temperature control module; The granulation tower body is made of metal and has a height of 35 to 45 meters. A dividing plate is provided near the top of the granulation tower, which divides the granulation tower into a working chamber and a cooling chamber. A mounting groove for installing the granulator is provided in the center of the dividing plate, and multiple ventilation holes are provided around the mounting groove on the dividing plate. The forced ventilation system includes multiple blowers located at the bottom of the granulation tower and air distributors connected to the air outlets of the blowers. The forced ventilation system is used to force an upward airflow to be formed in the cooling chamber. The exhaust gas treatment system includes an exhaust gas recovery pipe, an exhaust gas scrubber, a Venturi scrubber separator, and an exhaust gas return pipe connected in sequence. The exhaust gas recovery pipe is connected to the vent hole to collect the gas at the top of the cooling chamber. The exhaust gas return pipe reintroduces part of the exhaust gas treated by the Venturi scrubber separator back into the bottom of the granulation tower. The circulating air system includes a circulating air duct, which is used to re-introduce a portion of the exhaust gas from the cooling chamber near the working chamber back into the bottom of the granulation tower through the exhaust gas return pipe. The temperature control module adjusts the temperature inside the granulation tower by controlling the operating parameters of the blower unit and the reflux ratio of the exhaust gas return pipe.

[0007] By adopting the above technical solutions, the granulation tower is made of metal and has a height of 35-45 meters, which reduces investment and operating costs and shortens the construction period. The dividing plate divides the granulation tower into a working chamber and a cooling chamber, which facilitates exhaust gas recovery and granulation cooling. The forced ventilation system forms an upward airflow in the cooling chamber, which can better contact the slurry droplets coming down from the granulator. The circulating air system reintroduces part of the exhaust gas near the working chamber of the cooling chamber back to the bottom of the tower, which can replenish the gas volume and stabilize the gas temperature. The exhaust gas treatment system performs two-stage washing of the exhaust gas, which solves the difficulties in exhaust gas collection and treatment, and part of the treated exhaust gas can be reused. The temperature control module regulates the temperature inside the tower by controlling the blower operating parameters and the exhaust gas recirculation ratio, which can control the temperature of the particles at the bottom of the tower, thereby producing a variety of granular products and realizing "one tower for multiple uses".

[0008] Optionally, the forced ventilation system further includes a frequency converter connected to the blower, the frequency converter being used to adjust the speed of the blower and the number of times it starts and stops to control the gas flow rate in the granulation tower.

[0009] By adopting the above technical solution and using a frequency converter to adjust the speed and number of blowers, the gas flow rate in the granulation tower can be flexibly controlled, and the forced ventilation in the granulation tower can be precisely controlled. This is beneficial for controlling the temperature of the particles at the bottom of the tower, solving the problems of gas temperature at the bottom of the granulation tower and product quality. At the same time, the operating load of the device can be adjusted according to actual production needs.

[0010] Optionally, it also includes a return flow distribution system, which includes a first three-way regulating valve. The first air inlet and the air outlet of the first three-way regulating valve are connected to the exhaust gas return pipe. One end of the circulating air pipe is connected to the cooling chamber near the working chamber, and the other end is connected to the second air inlet of the first three-way regulating valve. The end of the exhaust gas return pipe away from the Venturi scrubbing separator is connected to the air distributor.

[0011] By adopting the above technical solution, the reflux distribution system guides a portion of the exhaust gas near the working chamber of the cooling chamber back through the circulating air duct. Combined with the treated exhaust gas in the exhaust gas reflux pipeline, the exhaust gas is recycled, reducing direct emissions, improving energy utilization, and reducing environmental pressure. The first three-way regulating valve can flexibly control the mixing ratio of the circulating air and the treated exhaust gas. The temperature characteristics of the reflux gas, combined with the temperature control module, can assist in regulating the temperature inside the tower, solving the problem of difficult temperature control of the product at the bottom of the tower, and improving product quality. The reflux gas is evenly distributed through the annular air distributor and the Λ-shaped guide hole, forming a stable upward airflow, enhancing the contact effect with the slurry droplets, and improving cooling efficiency and particle uniformity.

[0012] Optionally, a second three-way regulating valve is provided on the exhaust gas return pipe. The second three-way regulating valve is located upstream of the first three-way regulating valve. The air inlet and the first air outlet of the second three-way regulating valve are connected to the exhaust gas return pipe. An exhaust gas discharge pipe is provided at the second air outlet of the second three-way regulating valve.

[0013] By adopting the above technical solution, a second three-way regulating valve is installed on the exhaust gas return pipeline, and the second three-way regulating valve is located upstream of the first three-way regulating valve. Its air inlet and first air outlet are connected to the exhaust gas return pipeline, and an exhaust gas discharge pipe is installed at the second air outlet. The exhaust gas return ratio and discharge volume can be flexibly adjusted to achieve effective control of exhaust gas circulation and discharge. This ensures that there is a suitable gas environment in the granulation tower to maintain the normal operation of the process, and also discharges excess and qualified exhaust gas through the exhaust gas discharge pipe. This improves the flexibility and controllability of exhaust gas treatment and reduces the adverse impact on the production environment.

[0014] Optionally, the inlet of the exhaust gas scrubber is connected to a cooling water source; the inlet of the Venturi scrubber is connected to a cooling water source.

[0015] By adopting the above technical solution, during the treatment of granulation tail gas, the cooling water source provides washing liquid to the tail gas scrubber and Venturi scrubber separator, enabling fine washing of the tail gas. The tail gas scrubber performs pre-washing, washing relatively large dust particles from the gas phase into the liquid phase. The pre-washed dust-laden tail gas enters the inlet pipe of the Venturi scrubber separator through a pipeline. Subsequently, the gas velocity gradually increases in the contraction tube, reaching its maximum at the throat. Simultaneously, cooling water is sprayed into the gas phase through nozzles, atomized into fine droplets by the high-speed gas phase at the throat. Relying on the relative velocity between the gas and the droplets, efficient dust collection is achieved, removing fine micron-sized dust from the tail gas and ensuring that the tail gas meets emission standards. Simultaneously, it also reduces the tail gas temperature, which helps lower the temperature inside the granulation tower when the tail gas is returned. Furthermore, the increased concentration of the washing liquid, returned to the concentration process, reduces raw material consumption.

[0016] Optionally, the temperature control module includes a temperature sensor disposed in the cooling chamber and a control system. The control system is simultaneously connected to the temperature sensor, the first three-way regulating valve, the second three-way regulating valve and the frequency converter. The control system adjusts the operating parameters of the blower unit, the recirculation ratio of the exhaust gas recirculation pipe and the recirculation ratio of the circulating air duct based on the detection value of the temperature sensor.

[0017] By adopting the above technical solution, the granulation tower height is reduced and a metal tower body is used, increasing the degree to which the temperature inside the tower is affected by the environment. The temperature sensor can detect the temperature inside the cooling chamber, and the control system adjusts the operating parameters of the blower unit, the recirculation ratio of the exhaust gas return pipe, and the recirculation ratio of the circulating air duct based on the detected value, thereby accurately controlling the temperature inside the granulation tower. This solves the problems of gas temperature at the bottom of the granulation tower and product quality, and realizes the control of the air volume and temperature at the bottom of the tower. In this way, it can produce a variety of granular products and achieve the purpose of "one tower for multiple uses".

[0018] Optionally, the air distributor is an annular air distributor with an inner cavity. The outer ring wall of the air distributor fits with the inner wall of the granulation tower. The inner ring wall surface of the air distributor is provided with a plurality of inclined Λ-shaped guide holes. The axis of the Λ-shaped guide holes is set at an angle to the central axis of the granulation tower to guide the airflow upward.

[0019] By adopting the above technical solution, the outer ring wall of the annular air distributor is matched with the inner wall of the granulation tower, and the surface of the inner ring wall is provided with inclined Λ-shaped guide holes with its axis forming an angle with the central axis of the granulation tower. This allows the air distributor to better guide the airflow to rise in the granulation tower, improve the uniformity of airflow distribution, and thus enhance the contact effect between the material and the airflow in the granulation tower. This helps to optimize the granulation process and improve granulation quality and efficiency.

[0020] Optionally, the mounting groove is provided with a flange interface at its edge.

[0021] By adopting the above technical solution, the granulator can be stably connected to the granulation tower through the flange interface on the edge of the mounting groove, which facilitates the installation and disassembly of the granulator. Moreover, the flange interface can be used for granulators of different specifications, achieving the purpose of "one tower for multiple uses".

[0022] Optionally, the granulation tower is provided with a discharge port at the bottom, and a screw conveyor is connected to the discharge port.

[0023] By adopting the above technical solution, a discharge port is set at the bottom of the granulation tower and connected to a screw conveyor, which can facilitate the discharge of products from the granulation tower and achieve efficient product discharge.

[0024] Optionally, a scraper is provided at the bottom of the cooling chamber, and a drive motor is provided at the center of the bottom of the granulation tower. The drive motor is driven to the scraper to drive the scraper to rotate around the axis of the granulation tower.

[0025] By adopting the above technical solution, the material at the bottom of the cooling chamber can be scraped to the discharge port, which facilitates the discharge of the material and improves the discharge efficiency.

[0026] In summary, this application includes at least one of the following beneficial technical effects: 1. The granulation tower is made of metal and its height is reduced to 35-45 meters, which reduces construction costs, difficulty and time; 2. The forced ventilation system and the exhaust gas treatment system work together to collect the exhaust gas and perform two-stage washing, which solves the problem of difficult collection and treatment of exhaust gas in high towers; 3. The temperature control module regulates the temperature inside the granulation tower by controlling the operating parameters of the blower unit and the tail gas recirculation ratio, which solves the problem of difficult temperature control of the product particles at the bottom of the tower and improves product quality. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the granulation tower provided in the embodiments of this application, wherein the power source and circulating air duct of the granulator are not shown.

[0028] Figure 2 This is a schematic diagram of the internal structure of the granulation tower provided in the embodiments of this application, wherein the power source and circulating air duct of the granulator are not shown.

[0029] Figure 3 This is a simplified structural diagram of the closed-type low-tower granulation process device provided in the embodiments of this application.

[0030] Explanation of reference numerals in the attached drawings: 1-Granulation tower; 101-Divider plate; 1011-Installation groove; 1012-Ventilation hole; 102-Working chamber; 103-Cooling chamber; 104-Discharge port; 105-Feed pipe; 2-Granulator; 3-Blower; 4-Air distributor; 401-Λ-type guide hole; 5-Circulating air duct; 6-Tail gas recovery pipe; 7-Tail gas scrubber; 8-Venturi scrubber separator; 9-Tail gas return pipe; 10-First three-way regulating valve; 11-Second three-way regulating valve; 12-Screw discharge machine; 13-Scraper; 14-Drive motor; 15-First tail gas induced draft fan; 16-Second tail gas induced draft fan; 17-Third tail gas induced draft fan; 18-Tail gas discharge pipe. Detailed Implementation

[0031] The following is in conjunction with the appendix Figure 1-3 This application will be described in further detail.

[0032] This application discloses a closed-type low-tower granulation process apparatus.

[0033] like Figures 1-3 As shown, the closed-loop low-tower granulation process device includes a granulation tower 1, a granulator 2, a forced ventilation system, a circulating air system, an exhaust gas treatment system, and a temperature control module. The granulation tower 1 provides space for the entire granulation process, the granulator 2 is used to form granules from the slurry, the forced ventilation system can generate an upward airflow in the cooling chamber 103, the circulating air system can reintroduce some of the exhaust gas to the bottom of the tower, the exhaust gas treatment system treats the exhaust gas, and the temperature control module regulates the temperature inside the granulation tower 1. These components work together to achieve efficient and stable operation of the closed-loop low-tower granulation, reduce investment and operating costs, solve the exhaust gas treatment problem, and effectively control the temperature inside the tower to ensure product quality.

[0034] Specifically, the granulation tower 1 is constructed using metal materials, such as aluminum or stainless steel. Compared to traditional concrete structures, this material offers better corrosion resistance and higher strength, and is easier to install and maintain. The granulation tower 1 is 35-45 meters high, significantly reducing construction costs, difficulty, and time compared to traditional 95-110 meter towers. Near the top of the granulation tower 1 is a dividing plate 101, which divides the tower into a working chamber 102 and a cooling chamber 103. At the center of the dividing plate 101 is a mounting groove 1011 for installing the granulator 2. The mounting groove 1011 has flange interfaces along its edges, which can use standard flange connections. These flange interfaces facilitate the installation and disassembly of the granulator 2 while ensuring a tight seal. The working chamber 102 is equipped with a feed pipe 105 for supplying slurry to the granulator 2, and the feed pipe 105 is connected to the feed inlet of the granulator 2. The partition plate 101 is provided with multiple ventilation holes 1012 around the mounting groove 1011. The ventilation holes 1012 can be circular, square or other shapes, and their function is to enable the cooling chamber 103 to be connected to the exhaust gas treatment system.

[0035] Specifically, the forced ventilation system includes multiple blowers 3 located at the bottom of the granulation tower 1 and air distributors 4 connected to the air outlets of the blowers 3. In this embodiment, the number of blowers 3 is six, to reduce repetitive lines. Figure 3The diagram only shows the connection of one of the blowers 3. Six blowers 3 are equidistantly arranged around the granulation tower 1 along its axial direction. The blowers 3 can be centrifugal or axial flow blowers. Centrifugal blowers 3 have higher pressure and airflow, suitable for applications requiring higher pressure; axial flow blowers 3 have higher airflow and lower pressure, suitable for applications requiring larger airflow. The air distributor 4 is an annular air distributor 4 with an inner cavity. The outer ring wall of the air distributor 4 fits into the inner wall of the granulation tower 1, ensuring uniform airflow distribution. The inner ring wall surface of the air distributor 4 is provided with several inclined Λ-shaped guide holes 401. The axis of the Λ-shaped guide holes 401 is set at an angle to the central axis of the granulation tower 1 to guide the airflow upward. This design allows the airflow to be more evenly distributed within the cooling chamber 103, improving the cooling effect. The forced ventilation system also includes a frequency converter connected to the blower 3. The frequency converter can adjust the speed and number of times the blower 3 is started and stopped according to the actual needs in the granulation tower 1, thereby controlling the gas flow rate in the granulation tower 1.

[0036] Specifically, the exhaust gas treatment system includes an exhaust gas recovery pipe 6, an exhaust gas scrubber 7, a Venturi scrubbing separator 8, and an exhaust gas return pipe 9 connected in sequence. The exhaust gas recovery pipe 6 is connected to the vent 1012 and is used to collect the gas in the cooling chamber 103, introducing the dust-laden exhaust gas into the exhaust gas scrubber 7. In this embodiment, the exhaust gas recovery pipe 6 can be a ring structure near the top of the working chamber 102, with multiple branches extending from the ring structure corresponding one-to-one with the vent 1012, improving the exhaust gas collection efficiency while avoiding the power source (not shown in the figure) that provides power to the granulator 2. The exhaust gas scrubber 7 can be a packed-filler scrubber or a spray scrubber, and its function is to wash relatively large dust particles in the exhaust gas from the gas phase into the liquid phase. The Venturi scrubbing separator 8 can further wash away fine micron-sized dust in the exhaust gas. After two stages of washing, part of the exhaust gas meets the emission standards, and the other part is reintroduced to the bottom of the granulation tower 1 through the exhaust gas return pipe 9. The inlet ends of the exhaust gas scrubber 7 and the Venturi scrubber separator 8 are respectively connected to a cooling water source, which can provide the liquid required for cooling and scrubbing of the Venturi scrubber separator 8. In order to increase the exhaust gas recovery effect of the exhaust gas recovery pipe 6, a first exhaust gas induced draft fan 15 can be installed at the exhaust gas recovery pipe 6. The first exhaust gas induced draft fan 15 can promote the efficient collection of exhaust gas in the cooling chamber 103.

[0037] like Figure 3 As shown, the circulating air system includes a circulating air duct 5, which is used to reintroduce a portion of the exhaust gas from the cooling chamber 103 near the working chamber 102 back to the bottom of the granulation tower 1. Through the circulating air system, the exhaust gas at the top of the cooling chamber 103 can be fully utilized, improving energy efficiency while stabilizing the gas temperature at the bottom of the tower.

[0038] To achieve a reasonable distribution of circulating air and exhaust gas, the closed-loop low-tower granulation process unit also includes a reflux distribution system. The reflux distribution system includes a first three-way regulating valve 10. The first air inlet and air outlet of the first three-way regulating valve 10 are connected to the exhaust gas reflux pipe 9. One end of the circulating air pipe 5 is connected to the cooling chamber 103 near the working chamber 102, and the other end is connected to the second air inlet of the first three-way regulating valve 10. The end of the exhaust gas reflux pipe 9 away from the Venturi scrubbing separator 8 is connected to the air distributor 4.

[0039] The reflux distribution system guides a portion of the exhaust gas from the cooling chamber 103 near the working chamber 102 back through the circulating air duct 5. Combined with the treated exhaust gas from the exhaust gas return pipe 9, it achieves exhaust gas recycling, reduces direct emissions, improves energy utilization, and reduces environmental pressure. The first three-way regulating valve 10 can flexibly control the mixing ratio of the circulating air and the treated exhaust gas. The temperature characteristics of the reflux gas, combined with the temperature control module, can assist in adjusting the temperature inside the tower, solving the problem of difficult temperature control of the product at the bottom of the tower and improving product quality. The reflux gas is evenly distributed through the annular air distributor 4 and the Λ-shaped guide hole, forming a stable upward airflow, enhancing the contact effect with the slurry droplets, and improving cooling efficiency and particle uniformity.

[0040] In addition, the exhaust gas recovery pipe 6 of the exhaust gas treatment system collects the gas in the cooling chamber 103, reducing the gas accumulation in the cooling chamber 103 and thus reducing the pressure in the area above the granulation tower 1. The circulating air system guides part of the exhaust gas in the cooling chamber 103 back to the bottom of the tower, further reducing the gas retention at the top of the cooling chamber 103 and helping to reduce the pressure above. The forced ventilation system sends airflow into the cooling chamber 103 through the bottom blower 3 and the air distributor 4, directly increasing the pressure at the bottom of the cooling chamber 103. The exhaust gas guided back by the circulating air system and part of the treated exhaust gas returned by the exhaust gas treatment system jointly replenish the air volume at the bottom of the cooling chamber 103, further increasing the pressure below. The increase in the pressure difference between the top and bottom makes it easier for the rising airflow in the cooling chamber 103 to form and become more stable, allowing it to contact the slurry droplets falling from the granulator 2 more fully, improving cooling efficiency and ensuring the uniformity and quality stability of the granulated particles. At the same time, the stable rising airflow helps to reduce the local accumulation of dust in the tower and optimize the granulation environment.

[0041] A second three-way regulating valve 11 is installed on the exhaust gas recirculation duct 9. The second three-way regulating valve 11 is located upstream of the first three-way regulating valve 10. The air inlet and the first air outlet of the second three-way regulating valve 11 are connected to the exhaust gas recirculation duct 9. An exhaust gas discharge pipe 18 is installed at the second air outlet of the second three-way regulating valve 11. In order to increase the exhaust gas recirculation effect of the exhaust gas recirculation duct 9, a second exhaust gas induced draft fan 16 and a third exhaust gas induced draft fan 17 can be installed at the exhaust gas recirculation duct 9. The second exhaust gas induced draft fan 16 and the third exhaust gas induced draft fan 17 are located upstream and downstream of the second three-way regulating valve 11, respectively, to coordinate and regulate the dynamic balance between exhaust gas recirculation and emission.

[0042] Specifically, the temperature control module regulates the temperature inside the granulation tower 1 by controlling the operating parameters of the three blower groups and the recirculation ratio of the exhaust gas return pipe 9. The temperature control module includes a temperature sensor installed in the cooling chamber 103 and a control system. The control system is simultaneously connected to the temperature sensor, the first three-way regulating valve 10, the second three-way regulating valve 11, and the frequency converter. The temperature sensor can monitor the temperature inside the cooling chamber 103 in real time and transmit the temperature signal to the control system. Based on the temperature sensor's detection value, the control system adjusts the operating parameters of the three blower groups, the recirculation ratio of the exhaust gas return pipe 9, and the recirculation ratio of the circulating air duct 5, thereby achieving precise temperature control inside the granulation tower 1.

[0043] The granulation tower 1 has a discharge port 104 at its bottom, and a screw conveyor 12 is connected to the discharge port 104 to transport the granulated product out of the granulation tower 1. A scraper 13 is located at the bottom of the cooling chamber 103, and a drive motor 14 is located at the center of the bottom of the granulation tower 1. The drive motor 14 is connected to the scraper 13 to drive the scraper 13 to rotate around the axis of the granulation tower 1. The function of the scraper 13 is to scrape the granules at the bottom of the cooling chamber 103 to the discharge port 104, ensuring smooth discharge.

[0044] The implementation principle of the closed-loop low-tower granulation process device in this embodiment is as follows: By reducing the height of the granulation tower 1 and using metal material, the investment cost and operating expenses are greatly reduced. The setting of the forced ventilation system, circulating air system, and exhaust gas treatment system realizes closed-loop forced ventilation, solving the problem of exhaust gas collection and treatment, while improving energy utilization. The temperature control module can flexibly adjust the operating parameters of each system according to the actual temperature inside the granulation tower 1, ensuring the stability of the temperature inside the tower, thereby improving product quality. In addition, by changing the model of the granulator 2, different specifications of products can be produced, achieving the purpose of "one tower for multiple uses", which has significant improvements and advantages compared with the existing technology.

[0045] The above are all preferred embodiments of this application and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape and principle of this application should be covered within the scope of protection of this application.

Claims

1. A closed-loop low-tower granulation process apparatus, characterized in that, include: Granulation tower (1), granulator (2), forced ventilation system, circulating air system, exhaust gas treatment system and temperature control module; The granulation tower (1) is made of metal and has a height of 35 to 45 meters. The granulation tower (1) is provided with a dividing plate (101) near the top. The dividing plate (101) divides the granulation tower (1) into a working chamber (102) and a cooling chamber (103). The dividing plate (101) has an installation groove (1011) for installing the granulator (2) at the center. The dividing plate (101) has multiple ventilation holes (1012) around the installation groove (1011). The forced ventilation system includes a plurality of blowers (3) disposed at the bottom of the granulation tower (1) and an air distributor (4) connected to the air outlet of the blowers (3). The forced ventilation system is used to force an upward airflow to be formed in the cooling chamber (103). The exhaust gas treatment system includes an exhaust gas recovery pipe (6), an exhaust gas scrubber (7), a Venturi scrubber (8), and an exhaust gas return pipe (9) connected in sequence. The exhaust gas recovery pipe (6) is connected to the vent (1012) to collect the gas at the top of the cooling chamber (103). The exhaust gas return pipe (9) reintroduces part of the exhaust gas treated by the Venturi scrubber (8) back into the bottom of the granulation tower (1). The circulating air system includes a circulating air duct (5), which is used to re-introduce part of the exhaust gas from the cooling chamber (103) near the working chamber (102) into the bottom of the granulation tower (1) through the exhaust gas return pipe (9). The temperature control module adjusts the temperature inside the granulation tower (1) by controlling the operating parameters of the blower (3) and the reflux ratio of the exhaust gas reflux pipe (9).

2. The closed-loop low-tower granulation process apparatus according to claim 1, characterized in that, The forced ventilation system also includes a frequency converter connected to the blower (3), which is used to adjust the speed and number of starts and stops of the blower (3) to control the gas flow rate in the granulation tower (1).

3. The closed-loop low-tower granulation process apparatus according to claim 2, characterized in that, It also includes a return flow distribution system, which includes a first three-way regulating valve (10). The first air inlet and the air outlet of the first three-way regulating valve (10) are connected to the exhaust gas return pipe (9). One end of the circulating air pipe (5) is connected to the cooling chamber (103) near the working chamber (102), and the other end is connected to the second air inlet of the first three-way regulating valve (10). The end of the exhaust gas return pipe (9) away from the Venturi scrubbing separator (8) is connected to the air distributor (4).

4. The closed-loop low-tower granulation process apparatus according to claim 3, characterized in that, The exhaust gas return pipe (9) is provided with a second three-way regulating valve (11), which is located upstream of the first three-way regulating valve (10). The air inlet and the first air outlet of the second three-way regulating valve (11) are connected to the exhaust gas return pipe (9), and an exhaust gas discharge pipe (18) is provided at the second air outlet of the second three-way regulating valve (11).

5. The closed-loop low-tower granulation process apparatus according to claim 4, characterized in that, The inlet of the exhaust gas scrubber (7) is connected to a cooling water source; the inlet of the Venturi scrubber (8) is connected to a cooling water source.

6. The closed-loop low-tower granulation process apparatus according to claim 5, characterized in that, The temperature control module includes a temperature sensor and a control system installed in the cooling chamber (103). The control system is connected to the temperature sensor, the first three-way regulating valve (10), the second three-way regulating valve (11), and the frequency converter. The control system adjusts the operating parameters of the blower (3) group, the recirculation ratio of the exhaust gas recirculation pipe (9), and the recirculation ratio of the circulating air pipe (5) based on the detection value of the temperature sensor.

7. The closed-loop low-tower granulation process apparatus according to claim 1, characterized in that, The air distributor (4) is an annular air distributor (4). The air distributor (4) has an inner cavity. The outer ring wall of the air distributor (4) is fitted with the inner wall of the granulation tower (1). The inner ring wall surface of the air distributor (4) is provided with a plurality of inclined Λ-shaped guide holes (401). The axis of the Λ-shaped guide holes (401) is set at an angle to the central axis of the granulation tower (1) to guide the airflow upward.

8. The closed-loop low-tower granulation process apparatus according to claim 1, characterized in that, The mounting groove (1011) is provided with a flange interface at its edge.

9. The closed-loop low-tower granulation process apparatus according to claim 1, characterized in that, The granulation tower (1) is provided with a discharge port (104) at the bottom, and a screw conveyor (12) is connected to the discharge port (104).

10. The closed-loop low-tower granulation process apparatus according to claim 8, characterized in that, The bottom of the cooling chamber (103) is provided with a scraper (13), and the center of the bottom of the granulation tower (1) is provided with a drive motor (14). The drive motor (14) is driven to connect with the scraper (13) to drive the scraper (13) to rotate around the axis of the granulation tower (1).

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