Tower top ammonia removal and dust fall recovery device of urea prilling tower

Abstract

The utility model relates to the technical field of urea prilling towers, and particularly provides a urea prilling tower top ammonia removal and dust fall recovery device which comprises a carbon dioxide storage tank, a Venturi ejector, a spray pipe, a stainless steel wire net, a filter cloth bag, an induced draft fan, a back flushing pipeline and a factory air buffer tank. Carbon dioxide gas in the carbon dioxide storage tank enters the venturi ejector, process condensate enters the venturi ejector to form a gas-liquid mixture with carbon dioxide, the gas-liquid mixture enters the spraying pipe to be sprayed out, and a water mist film containing the carbon dioxide gas is formed on the stainless steel wire net. And the water mist film is in contact reaction with air containing free ammonia and urea dust from the prilling tower on the stainless steel wire mesh, so that the effects of fixing ammonia and reducing dust are achieved. The induced draft fan above the filter cloth bag has the suction effect, and the gas is filtered by the filter cloth bag, so that the effect of further reducing dust is achieved. The back flushing pipeline is used for washing and back flushing and drying the filter cloth bag, and the effect that the filter cloth bag can be repeatedly used for dust falling is achieved.

Description

Technical Field

[0001] The utility model relates to the technical field of urea granulation towers, in particular to an ammonia removal and dust recovery device at the top of a urea granulation tower. Background Art

[0002] At present, there are many kinds of dust recovery devices on the top of granulation towers in urea production enterprises, but the recovery effects are not very ideal.

[0003] The dust recovery device on the top of the urea granulation tower, whether it is dry dust removal or wet dust removal, has an unstable operation cycle, serious deviation of the fan on the top of the tower, frequent flushing, and uneven distribution of the bags on the top of the tower, resulting in different bag adhesion and uneven air volume.

[0004] Furthermore, the existing urea granulation tower top dust recovery device is not equipped with an ammonia removal device at the same time. Ammonia is a toxic and harmful gas, and if it is not removed, it will seriously pollute the environment. Utility Model Content

[0005] The utility model aims to overcome the defects in the prior art and provide a device for recovering dust from the top of a urea granulation tower and fixing free ammonia at the same time, so as to prevent the gaseous ammonia and dust discharged from the top of the urea granulation tower from polluting the environment.

[0006] In order to achieve the above purpose, the technical solution adopted by the utility model is:

[0007] A urea granulation tower top ammonia removal and dust reduction recovery device, comprising: a filter area, an induced draft fan, a carbon dioxide storage tank, a venturi ejector, a spray pipe and a stainless steel wire mesh;

[0008] The carbon dioxide storage tank is connected to the Venturi injector, the Venturi injector is connected to the spray pipe, the spray pipe is arranged on the stainless steel wire mesh, and the stainless steel wire mesh is arranged on the top of the urea granulation tower;

[0009] The filter area is arranged above the stainless steel wire mesh, and the induced draft fan is arranged above the filter area;

[0010] The carbon dioxide storage tank is provided with a carbon dioxide solenoid valve and a carbon dioxide pressure regulating valve, the carbon dioxide storage tank is connected to the carbon dioxide gas through the carbon dioxide pressure regulating valve, and the carbon dioxide gas in the carbon dioxide storage tank is connected to the Venturi injector through the carbon dioxide solenoid valve;

[0011] The venturi ejector is provided with a process condensate regulating valve 1, and the venturi ejector is connected to the process condensate through the process condensate regulating valve 1, so that the process condensate and carbon dioxide form a gas-liquid mixture;

[0012] The spray pipe is used to spray the gas-liquid mixture toward the stainless steel wire mesh to form a water mist film or water curtain containing carbon dioxide gas on the stainless steel wire mesh;

[0013] The filtration area includes: filter bags, filter bag frames, bag fixing plates, and filter cartridge flower plates; the filter cartridge flower plates are flat and have several holes; there are several filter bag frames, and the upper ends of the filter bag frames are respectively connected to the holes of the filter cartridge flower plates to form filter bag frame outlets, and the lower ends of the filter bag frames are fixed by bag fixing plates to prevent the filter bag frames from drifting back and forth; there are several filter bags, which are respectively wrapped around the outside of the filter bag frames.

[0014] As a further technical solution, the bottom of the filter bag frame has a stainless steel round steel, which is used to connect and fix with the cloth bag fixing plate; the filter bag frame and the filter cartridge plate are fixed with threads to prevent the filter bag frame from falling off.

[0015] As a further technical solution, the filter bag is a polyester film.

[0016] As a further technical solution, the ammonia removal and dust recovery device at the top of a urea granulation tower also includes: a backflush pipeline and a factory air buffer tank; the factory air buffer tank is connected to the backflush pipeline; the factory air buffer tank is provided with a factory air pressure regulating valve and a factory air regulating valve, the factory air buffer tank is connected to the factory air through the factory air pressure regulating valve, and the factory air is connected to the backflush pipeline through the factory air regulating valve; the backflush pipeline is also connected to a second process condensate regulating valve to connect the process condensate; the backflush pipeline is provided with a backflush pipe port corresponding to the filter bag, and the backflush pipeline is also provided with a backflush air solenoid valve, and the backflush air solenoid valve is used to control the air or process condensate in the backflush pipeline to be discharged from the backflush pipe port.

[0017] As a further technical solution, the filter cartridge flower plate is a circular flat plate, and several holes distributed thereon are arranged in a fan shape; the filter bags are arranged in a fan shape and are divided into a plurality of fan-shaped areas; each fan-shaped area is independently provided with two or more induced draft fans; each fan-shaped area is independently provided with the back-blowing pipeline, and the back-blowing pipelines are all connected by detachable short tubes, and each short tube has a back-blowing pipe opening corresponding to the filter bag, and the distance between the back-blowing pipe opening and the filter bag skeleton outlet on the filter cartridge flower plate is 20-50mm; each fan-shaped area is divided into four or more groups, and each group of each fan-shaped area is provided with the back-blowing air solenoid valve control.

[0018] As a further technical solution, the pipeline connecting the factory air buffer tank to the backflush pipeline is configured to be an inverted U-shape.

[0019] As a further technical solution, the spray pipe is a ring pipe with spray holes on it.

[0020] As a further technical solution, the air velocity of the spray hole is 1 m / s.

[0021] As a further technical solution, the ammonia removal and dust recovery device at the top of a urea granulation tower also includes: a water holding layer, arranged at the lower part of the stainless steel wire mesh; a stainless steel wire mesh support is provided at the upper end of the water holding layer, and the stainless steel wire mesh support is connected to the lower end of the stainless steel wire mesh to support the stainless steel wire mesh.

[0022] As a further technical solution, the ammonia removal and dust reduction recovery device at the top of the urea granulation tower also includes: a top fan, which is arranged at the uppermost end of the top of the urea granulation tower.

[0023] The beneficial effects of the utility model are:

[0024] The utility model is provided with a carbon dioxide storage tank, a venturi ejector, a spray pipe and a stainless steel wire mesh. The carbon dioxide gas in the carbon dioxide storage tank enters the venturi ejector, and the process condensate enters the venturi ejector to form a gas-liquid mixture with the carbon dioxide and enters the spray pipe for spraying, thereby forming a water mist film containing carbon dioxide gas on the stainless steel wire mesh. The water mist film contacts and reacts with the air containing free ammonia and urea dust from the granulation tower on the stainless steel wire mesh, thereby achieving the effect of fixing ammonia and reducing dust.

[0025] The utility model arranges filter bags on the top of the granulation tower in a fan-shaped distribution, and the gas is filtered by the filter bags through the suction action of the induced draft fan above the filter bags, which has the effect of further reducing dust.

[0026] The utility model is provided with a back-blowing pipeline, which is used for washing the filter bag with water and can also back-blow and dry the filter bag, so that the filter bag can be repeatedly used for dust reduction. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 A schematic diagram of the structure of the ammonia solidification and dust reduction part and the filter bag part of an embodiment of the utility model;

[0028] Figure 2 A schematic diagram of the fan-shaped arrangement of filter bags in one embodiment of the utility model;

[0029] Figure 3 Schematic diagram of the fan-shaped area backwashing and flushing structure of the filter bag and the backwashing filter bag area grouping structure in one embodiment of the utility model;

[0030] Figure 4 A schematic diagram of the overall structure of an embodiment of the utility model.

[0031] Figure 5 A schematic diagram of the connection between a filter bag frame and a bag fixing plate according to an embodiment of the utility model.

[0032] Figure 6 A schematic diagram of the connection between the filter cartridge flower plate and the filter bag frame in one embodiment of the utility model.

[0033] Reference numerals:

[0034] 1. Carbon dioxide storage tank, 2. Venturi ejector, 3. Carbon dioxide solenoid valve, 4. Carbon dioxide pressure regulating valve, 5. Process condensate regulating valve one, 6. Spray pipe, 7. Stainless steel wire mesh, 8. Stainless steel wire mesh support, 9. Stainless steel wire mesh vertical angle, 10. Filtration area, 11. Bag fixing plate, 12. Filter cartridge plate, 13. Draft fan, 14. Back-blowing solenoid valve, 15. Factory air regulating valve, 16. Process condensate regulating valve two, 17. Factory air buffer tank, 18. Factory air pressure regulating valve, 19. Tower top fan. DETAILED DESCRIPTION

[0035] The utility model is further described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0036] like Figure 1-4 As shown, an embodiment of the utility model is a urea granulation tower top ammonia removal and dust recovery device, which includes: a filtering area 10, an induced draft fan 13, a carbon dioxide storage tank 1, a venturi injector 2, a spray pipe 6 and a stainless steel wire mesh 7.

[0037] The carbon dioxide storage tank 1 is connected to the venturi injector 2, the venturi injector 2 is connected to the spray pipe 6, the spray pipe 6 is arranged on the stainless steel wire mesh 7, and the stainless steel wire mesh 7 is arranged on the top of the urea granulation tower.

[0038] The filter area 10 is arranged above the stainless steel wire mesh 7 at the top of the urea granulation tower. The induced draft fan 13 is arranged above the filter area 10.

[0039] The carbon dioxide storage tank 1 is provided with a carbon dioxide solenoid valve 3 and a carbon dioxide pressure regulating valve 4. The carbon dioxide storage tank 1 is connected to the carbon dioxide gas through the carbon dioxide pressure regulating valve 4, and the carbon dioxide gas in the carbon dioxide storage tank 1 is connected to the venturi injector 2 through the carbon dioxide solenoid valve 3; the venturi injector 2 is provided with a process condensate regulating valve 5, and the venturi injector 2 is connected to the process condensate through the process condensate regulating valve 5, so that the process condensate and carbon dioxide form a gas-liquid mixture; the gas-liquid mixture enters the spray pipe 6, and the spray pipe 6 is used to spray the gas-liquid mixture onto the stainless steel wire mesh 7 to form a water mist film or water curtain containing carbon dioxide gas on the stainless steel wire mesh 7.

[0040] The filter area 10 includes: a filter bag, a filter bag frame, a filter bag fixing plate 11 and a filter cartridge flower plate 12 .

[0041] The filter cartridge flower plate 12 is flat and has several holes distributed thereon; there are several filter bag frames, the upper ends of each filter bag frame are respectively connected to the holes of the filter cartridge flower plate to form a filter bag frame outlet, and the lower ends of each filter bag frame are fixed by a bag fixing plate 11 to prevent the filter bag frame from drifting back and forth; there are several filter bags, which are respectively wrapped around the outside of each filter bag frame.

[0042] The filter bag is made of polyester film with excellent permeability. The filter bag is fixed on the filter bag frame by buckles.

[0043] like Figure 5 As shown, there is a stainless steel round steel at the bottom of the filter bag frame, and the head of the round steel can be a thread or a round hole to facilitate connection and fixation with the bag fixing plate 11.

[0044] like Figure 6 As shown, the filter bag frame and the filter cartridge plate 12 are fixed by threads to prevent the filter bag frame from falling off. The filter cartridge plate is an internal thread, and the top of the filter bag frame is an external thread.

[0045] There may be two, four or more carbon dioxide storage tanks 1; there may be two, four or more venturi ejectors 2; there may be two, four or more carbon dioxide solenoid valves 3.

[0046] The number of the spray pipes 6 can be two, three or more. The spray pipe 6 is an annular pipe with spray holes. The air velocity of the spray holes is preferably about 1 m / s. The air velocity must be controlled to ensure that the carbon dioxide gas moves downward along the mesh surface of the stainless steel wire mesh 7 with water mist droplets to form a water mist film or water curtain of water + carbon dioxide on the mesh surface. The spray pipes 6 can be arranged on the stainless steel wire mesh 7 in layers.

[0047] The stainless steel wire mesh 7 is provided with a fixing device to be fixed on the top of the urea granulation tower. The flow area of ​​the stainless steel wire mesh 7 can meet the maximum ventilation volume in the urea granulation tower. The stainless steel wire mesh 7 is a woven mesh, and the mesh holes can be square holes or long holes.

[0048] The upper end of the stainless steel wire mesh 7 is fixedly connected to the vertical wall at the top of the urea granulation tower. The angle between the upper end of the stainless steel wire mesh 7 and the vertical wall at the top of the urea granulation tower is a vertical angle 9 of the stainless steel wire mesh. The vertical angle 9 of the stainless steel wire mesh is preferably 30-60°. The vertical angle 9 of the stainless steel wire mesh is used to ensure that the water sprayed from the upper spray pipe 6 in the parking state will not flow into the granulation tower by gravity.

[0049] The utility model arranges a stainless steel wire mesh on the top of a urea granulation tower, forms a water mist film on the stainless steel wire mesh, and contains carbon dioxide gas in the water mist film. The wet carbon dioxide gas contacts and reacts with air containing free ammonia and urea dust from the urea granulation tower on the stainless steel wire mesh. Therefore, after the air containing free ammonia and urea dust in the urea granulation tower passes through the wet stainless steel wire mesh dissolved with carbon dioxide, most of the free ammonia and dust are fixed, which has the effect of fixing ammonia and reducing dust.

[0050] The utility model arranges a filter area above the stainless steel wire mesh, and the induced draft fan above the filter area has a suction effect, so that the moist gas enters the filter area, and the moist gas is filtered by the filter bag in the filter area, thereby having a further dust reduction effect.

[0051] The utility model embodiment of a urea granulation tower top ammonia removal and dust recovery device also includes: a water storage layer, which is arranged at the lower part of the stainless steel wire mesh 7 to carry the water sprayed from the spray pipe 6 and the water flowing down from the stainless steel wire mesh 7.

[0052] A stainless steel wire mesh support 8 is provided at the upper end of the water storage layer, and the stainless steel wire mesh support 8 is connected to the lower end of the stainless steel wire mesh 7 to support the stainless steel wire mesh 7.

[0053] The ammonia removal and dust reduction recovery device for the top of a urea granulation tower according to the embodiment of the utility model further includes: a backflush pipeline and a factory air buffer tank 17 .

[0054] The factory air buffer tank 17 is connected to the backflush pipeline. The factory air buffer tank 17 is provided with a factory air pressure regulating valve 18 and a factory air regulating valve 15. The factory air buffer tank 17 is connected to the factory air through the factory air pressure regulating valve 18, and the factory air is connected to the backflush pipeline through the factory air regulating valve 15.

[0055] The backflush pipeline is also connected to the process condensate regulating valve 2 16 to access the process condensate.

[0056] The backflush pipeline is provided with a backflush pipe port corresponding to the filter bag, and is also provided with a backflush air solenoid valve 14, which is used to control the air or process condensate in the backflush pipeline to be discharged from the backflush pipe port.

[0057] When the backflush pipeline is connected to the process condensate, the filter bags can be washed with water through the backflush pipe port; after washing, the backflush pipeline is connected to the factory air, and the filter bags can be backflush dried through the backflush pipe port.

[0058] The pipeline connecting the plant air buffer tank 17 to the backwash pipeline is designed in an inverted U shape to prevent the process condensate in the backwash pipeline from entering the plant air buffer tank 17 .

[0059] The filter cartridge plate 12 is a circular flat plate, and several holes distributed thereon are arranged in a fan shape, so the filter bags are arranged in a fan shape at the top of the tower. The filter bags are arranged in a fan shape at the top of the tower, and the entire circular tower top is divided into multiple fan-shaped areas, which can be 4, 8, 12 or more. Each fan-shaped area is individually provided with a minimum of two induced draft fans or according to design requirements. Each fan-shaped area is individually provided with a back-blowing pipeline, and the back-blowing pipelines are connected by detachable short tubes, and each short tube has a back-blowing pipe opening corresponding to the filter bag, and the distance between the back-blowing pipe opening and the filter bag skeleton outlet on the filter cartridge plate 12 is between 20-50mm. The back-blowing of each fan-shaped area can be divided into four or more groups of back-blowing, and the back-blowing group of each fan-shaped area is controlled by a back-blowing gas solenoid valve, and each fan-shaped area has 4 or more back-blowing gas solenoid valves.

[0060] like Figure 4 In the illustrated embodiment, the back-blowing of each sector-shaped area is divided into four groups. Each back-blowing group of each sector-shaped area is controlled by a back-blowing solenoid valve. There are four back-blowing solenoid valves in each sector-shaped area.

[0061] The filter bags are arranged in a fan-shaped pattern. The advantage of grouping each fan-shaped area is that the filter bags can be set to be washed and back-blown and dried simultaneously. The washing and back-blown drying of the filter bags can also be carried out simultaneously with filtering, and there is no need to stop the machine to wash and back-blown the filter bags separately. Therefore, the filtering function of the filter bags is not affected when the filter bags are washed and back-blown and dried. For example, some fan-shaped filter bags are filtered, some fan-shaped filter bags are washed, and other fan-shaped filter bags are back-blown and dried; in a fan-shaped area, the filter bags of fan-shaped areas can be washed and back-blown and dried in groups, such as group 1, group 2, group 3, and group 4 are washed in turn, and then group 1, group 2, group 3, and group 4 are back-blown and dried in turn, so as to ensure the washing flow of the filter bags in a group of fan-shaped areas, or the ventilation air volume during back-blown drying.

[0062] The embodiment of the utility model provides a urea granulation tower top ammonia removal and dust reduction recovery device, which further includes: a tower top fan 19, which is arranged at the top of the urea granulation tower. The air in the urea granulation tower is filtered by a bag and then drawn out by the tower top fan 19 and sent into the atmosphere.

[0063] The operation mode of the utility model is as follows:

[0064] Solid ammonia dust reduction: The carbon dioxide gas of about 1.0MPaA from the outside is pressurized into the carbon dioxide storage tank 1 through the carbon dioxide pressure regulating valve 4, and the pressure of the carbon dioxide storage tank 1 is controlled between 0.3-0.5MPaA. The gas in the carbon dioxide storage tank 1 enters the venturi injector 2 through the carbon dioxide solenoid valve 3, and the process condensate enters the venturi injector 2 through the process condensate regulating valve 5, forms a gas-liquid mixture with carbon dioxide and enters the spray pipe 6, and is sprayed out through the small holes on the pipe. The process condensate forms a water mist film on the stainless steel wire mesh 7, and the water mist film contains carbon dioxide gas. The moist carbon dioxide gas contacts and reacts with the air containing free ammonia and urea dust from the granulation tower on the stainless steel wire mesh 7, which has the effect of solid ammonia dust reduction.

[0065] Dust reduction: The filter bags at the top of the granulation tower are distributed in a fan shape. After passing through the moistened stainless steel wire mesh 7 dissolved with carbon dioxide, most of the free ammonia and dust have been fixed. The moist gas is attracted by the induced draft fan 13 and enters the filtration area for filtration, which has the effect of dust reduction. Finally, the gas is filtered by the bag and then sucked out by the tower top fan 19 into the atmosphere.

[0066] The above embodiments are only for illustrating the technical concept and features of the utility model, and their purpose is to enable people familiar with the technology to understand the content of the utility model and implement it accordingly, and they cannot be used to limit the protection scope of the utility model. Any equivalent changes or modifications made according to the spirit of the utility model should be included in the protection scope of the utility model.

Claims

1. A urea granulation tower top ammonia removal and dust recovery device, characterized in that: It includes: Filtration area, induced draft fan, CO2 storage tank, venturi ejector, spray pipe and stainless steel wire mesh; The carbon dioxide storage tank is connected to the Venturi injector, the Venturi injector is connected to the spray pipe, the spray pipe is arranged on the stainless steel wire mesh, and the stainless steel wire mesh is arranged on the top of the urea granulation tower; The filter area is arranged above the stainless steel wire mesh, and the induced draft fan is arranged above the filter area; The carbon dioxide storage tank is provided with a carbon dioxide solenoid valve and a carbon dioxide pressure regulating valve, the carbon dioxide storage tank is connected to the carbon dioxide gas through the carbon dioxide pressure regulating valve, and the carbon dioxide gas in the carbon dioxide storage tank is connected to the Venturi injector through the carbon dioxide solenoid valve; The venturi ejector is provided with a process condensate regulating valve 1, and the venturi ejector is connected to the process condensate through the process condensate regulating valve 1, so that the process condensate and carbon dioxide form a gas-liquid mixture; The spray pipe is used to spray the gas-liquid mixture toward the stainless steel wire mesh to form a water mist film or water curtain containing carbon dioxide gas on the stainless steel wire mesh; The filtration area includes: filter bags, filter bag frames, bag fixing plates, and filter cartridge flower plates; the filter cartridge flower plates are flat and have several holes; there are several filter bag frames, and the upper ends of the filter bag frames are respectively connected to the holes of the filter cartridge flower plates to form filter bag frame outlets, and the lower ends of the filter bag frames are fixed by bag fixing plates to prevent the filter bag frames from drifting back and forth; there are several filter bags, which are respectively wrapped around the outside of the filter bag frames.

2. The urea granulation tower top ammonia removal and dust reduction recovery device according to claim 1, characterized in that: The bottom of the filter bag frame is provided with a stainless steel round steel bar, which is used to connect and fix with the bag fixing plate; The filter bag frame and the filter cartridge plate are fixed with threads to prevent the filter bag frame from falling off.

3. The urea granulation tower top ammonia removal and dust reduction recovery device according to claim 2, characterized in that: The filter bag is a polyester film.

4. A urea granulation tower top ammonia removal and dust reduction recovery device as claimed in claim 1, 2 or 3, characterized in that: It also includes: backflush lines, plant air buffer tanks; The factory air buffer tank is connected to the backflush pipeline; The factory air buffer tank is provided with a factory air pressure regulating valve and a factory air regulating valve, the factory air buffer tank is connected to the factory air through the factory air pressure regulating valve, and the factory air is connected to the backflush pipeline through the factory air regulating valve; The backflush pipeline is also connected to a second process condensate regulating valve to access the process condensate; The back-blowing pipeline is provided with a back-blowing pipe port corresponding to the filter bag, and the back-blowing pipeline is also provided with a back-blowing air solenoid valve, and the back-blowing air solenoid valve is used to control the air or process condensate in the back-blowing pipeline to be discharged from the back-blowing pipe port.

5. The urea granulation tower top ammonia removal and dust reduction recovery device as claimed in claim 4, characterized in that: The filter cartridge flower plate is a circular flat plate, and a plurality of holes distributed thereon are arranged in a fan shape; The filter bags are arranged in a fan shape and divided into a plurality of fan-shaped areas; Each sector area is equipped with two or more induced draft fans; Each sector area is provided with a back-blowing pipeline separately, and the back-blowing pipelines are connected to each other with detachable short tubes, each short tube has a back-blowing pipe opening corresponding to the filter bag, and the distance between the back-blowing pipe opening and the filter bag skeleton outlet on the filter cartridge plate is 20-50mm; Each sector area is divided into more than four groups, and each group of each sector area is provided with the back-blowing solenoid valve control.

6. The urea granulation tower top ammonia removal and dust reduction recovery device according to claim 4, characterized in that: The pipeline connecting the factory air buffer tank to the backflush pipeline is configured in an inverted U shape.

7. A urea granulation tower top ammonia removal and dust reduction recovery device as claimed in claim 1, 2 or 3, characterized in that: The spray pipe is a ring pipe, and a spray hole is arranged on the ring pipe.

8. The urea granulation tower top ammonia removal and dust reduction recovery device according to claim 7, characterized in that: The air velocity of the spray hole is 1 m / s.

9. A urea granulation tower top ammonia removal and dust reduction recovery device as claimed in claim 1, 2 or 3, characterized in that: It also includes: a water-holding layer, which is arranged at the lower part of the stainless steel wire mesh; A stainless steel wire mesh support is provided at the upper end of the water-containing layer, and the stainless steel wire mesh support is connected to the lower end of the stainless steel wire mesh to support the stainless steel wire mesh.

10. A urea granulation tower top ammonia removal and dust reduction recovery device as claimed in claim 1, 2 or 3, characterized in that: It also includes: a tower top fan, which is arranged at the top of the urea granulation tower.

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