A gravity type seawater desalination pretreatment device and process thereof

Abstract

The present application relates to the field of seawater desalination treatment, in particular to a gravity type seawater desalination pretreatment device and process. The gravity type seawater desalination pretreatment device comprises a tank body and a platform railing fixedly installed outside the tank body, the bottom of the tank body is provided with a water distribution reaction mechanism, and the lower portion of the water distribution reaction mechanism is further provided with a sludge discharge mechanism, the middle portion of the tank body is provided with a gas washing gas distribution mechanism, and the upper portion of the gas washing gas distribution mechanism is further provided with a nanoscale separation mechanism, and the top of the tank body is provided with a clean water discharge mechanism. The seawater is sucked into the tank body through the integrated design of the tank body, the sucked seawater and impurities are layered, the sludge is discharged downward, and the water rises upward. The water can be filtered through the membrane tube during the rising process. The filtered water finally flows into the surrounding frame through the overflow weir and is then discharged by the drain pipe. The integrated pretreatment device solves the problems of multiple pretreatment structures, large land occupation and high cost.

Description

Technical Field

[0001] This invention relates to the field of seawater desalination, specifically to a gravity-type seawater desalination pretreatment device and its process. Background Technology

[0002] Currently, the main pretreatment processes for seawater desalination include:

[0003] 1. Coagulation sedimentation, V-type filter, ultrafiltration;

[0004] 2. Air flotation, V-type filter, ultrafiltration;

[0005] 3. Coagulation sedimentation, air flotation, V-type filter, ultrafiltration.

[0006] The above process flow is long, requires a large investment and land area, the process parameters of each individual process have a great influence on each other, the operation and management are difficult, it is greatly affected by human factors, and the quality and quantity of the effluent are unstable.

[0007] Coagulation sedimentation and flotation processes are significantly affected by the quality and temperature of the incoming water, as well as the dosage of chemicals, directly impacting the effluent quality and severely hindering the normal operation of subsequent desalination processes. Therefore, we propose a gravity-type seawater desalination pretreatment device and its process. Summary of the Invention

[0008] The purpose of this invention is to provide a gravity-type seawater desalination pretreatment device and process to solve the problems mentioned in the background art.

[0009] To achieve the above objectives, the present invention provides the following technical solution: a gravity-type seawater desalination pretreatment device, comprising a tank and a platform railing fixedly installed outside the tank, a water distribution reaction mechanism at the bottom of the tank, a sludge discharge mechanism below the water distribution reaction mechanism, an air washing and air distribution mechanism in the middle of the tank, a nanoscale separation mechanism above the air washing and air distribution mechanism, and a purified water discharge mechanism at the top of the tank.

[0010] Preferably, the water distribution reaction mechanism includes a conical hopper fixedly disposed on the lower inner side of the tank body, and a water inlet intermediate pipe horizontally disposed above the conical hopper. One end of the water inlet intermediate pipe is fixedly inserted through the tank body, and the other end of the water inlet intermediate pipe faces the center of the conical hopper. A water inlet distributor is also fixedly disposed at the end of the water inlet intermediate pipe facing the conical hopper. The cone top of the conical hopper is open. Two manholes are also connected to the outer wall of the tank body, and the manholes are located on the upper and lower sides of the conical hopper, respectively. Seawater that needs to be pretreated for desalination is transported to the inside of the tank body through the water inlet intermediate pipe and the water inlet distributor by a suction pump.

[0011] Preferably, the sludge discharge mechanism includes a three-way pipe fixedly connected to the bottom end of the conical hopper. The other two ends of the three-way pipe are respectively connected to a sludge discharge pipe and a high-pressure water inlet pipe. The ends of the sludge discharge pipe and the high-pressure water inlet pipe away from the three-way pipe both extend to the outside of the tank body. The high-pressure water inlet pipe can be connected to a high-pressure water source to flush the sludge inside the sludge discharge pipe.

[0012] Preferably, the gas washing and air distribution mechanism includes an annular pipe disposed above the conical hopper, and the annular pipe is coaxially installed with the conical hopper. An air distribution pipe is fixedly connected to the outer side of the annular pipe, and the other end of the air distribution pipe extends to the outside of the tank body. Several air outlet pipes are fixedly connected to the upper and lower ends of the annular pipe in a circumferentially equidistant manner. By designing several air outlet pipes on the surface of the annular pipe, high-pressure gas can be uniformly used to wash and flush the membrane tube and the conical hopper.

[0013] Preferably, the nanoscale separation mechanism includes a porous plate fixedly installed on the top of the tank, and a plurality of membrane tubes are embedded inside the porous plate. The top of each membrane tube is fixedly connected to the porous plate by a gasket. An exhaust pipe is also fixedly installed at the center of the porous plate, with the two ends of the exhaust pipe located above and below the porous plate, respectively. The membrane tubes are made of PTFE material. Because the surface of the PTFE membrane is very smooth, particles attached to the surface of the membrane tube will automatically fall off and sink into the lower sludge discharge area when they grow to a certain size.

[0014] Preferably, the water purification discharge mechanism includes an overflow weir fixedly installed on the top of the tank, and the drainage height of the overflow weir is greater than the height of the upper end of the membrane tube extending out of the perforated plate. A frame is also fixedly fitted around the top periphery of the tank, and the lower end face of the frame is lower than the lower end face of the perforated plate. A drain pipe is also fixedly installed at the bottom of the frame, that is, the purified water will flow out through the overflow weir and finally be discharged through the drain pipe.

[0015] Preferably, a sludge scraping assembly is provided between the conical bucket and the three-way pipe, and a driving assembly is provided on the outside of the sludge scraping assembly, and an auxiliary flushing assembly is provided inside the sludge discharge pipe;

[0016] The sludge scraping assembly includes a central shaft coaxially disposed inside the three-way pipe. The central shaft rotatably passes through the three-way pipe, and the bottom of the central shaft is rotatably embedded inside the tank body. The upper end face of the conical hopper is provided with several arc-shaped sludge scraping blades distributed equidistantly in a circle. The end of the arc-shaped sludge scraping blade near the central shaft is fixedly connected to the central shaft with a connecting rod. The outer surface of the central shaft is also fixedly provided with a spiral blade, and the spiral blade is generally shuttle-shaped. The end of the arc-shaped sludge scraping blade away from the central shaft has a large bend angle. During the sludge scraping process, the sludge will flow back and slide down the conical hopper.

[0017] Preferably, the drive assembly includes a worm gear fixedly sleeved at the bottom of the central shaft, and a worm is meshed with the outside of the worm gear. An electric motor is fixedly installed on the outside of the tank, and a drive rod is provided at the output end of the electric motor. The drive rod rotatably passes through the tank, and the worm is fixedly sleeved on the outside of the drive rod. The electric motor drives the worm to rotate, thereby causing the worm gear to rotate with the central shaft.

[0018] Preferably, the auxiliary flushing assembly includes a plurality of columns fixed axially inside the sludge discharge pipe, each column having an extension component inside and a trigger component at its lower end;

[0019] The extension component includes a receiving slot inside the column, and two symmetrically distributed blocking blocks are placed inside the receiving slot. Each blocking block has a missing gear fixedly installed at its bottom, and the missing gear is hinged to the column. A rack is meshed between the two missing gears. A slider that is slidably embedded inside the column is fixedly installed at the bottom of the rack. A spring is provided between the upper part of the slider and the column, and an actuating rod that slides through the column is fixedly installed at the lower part of the slider. When the rack moves upward, the two blocking blocks can be opened simultaneously through the meshing of the rack and the missing gear.

[0020] The triggering component includes a turntable located below each trigger rod. Each turntable and trigger rod are eccentrically positioned. An arc-shaped lifting block is fixedly installed at the upper end of each turntable, and a rotating shaft that is rotatably embedded inside the tank is fixedly installed at the bottom of each turntable. A synchronous gear is fixedly sleeved on the outer surface of several rotating shafts and the central shaft, and a synchronous toothed belt is provided for transmission among the several synchronous gears. The rotation of the central shaft can drive the rotating shafts and turntables to rotate through the synchronous gears and synchronous toothed belt.

[0021] A pretreatment process for a gravity-type seawater desalination pretreatment device includes the following steps:

[0022] S1. During the water intake stage, the seawater that needs to be desalinated is pumped through the intermediate water intake pipe into the tank. As the seawater enters the tank, the silt and sand mixed in with it will be deposited at the top of the conical bucket, while the water will rise slowly step by step.

[0023] S2, the sewage discharge stage, the conical bucket guides the deposited silt and sand into the interior of the three-way pipe, and finally discharges it through the sludge discharge pipe;

[0024] S3, the fine filtration stage, the rising seawater enters the interior of the membrane tube. The membrane layer of the membrane tube can filter nanoscale dirt, allowing the filtered water to overflow through the overflow weir and finally be discharged through the drain pipe.

[0025] Compared with the prior art, the beneficial effects of the present invention are:

[0026] 1. This invention uses an integrated tank design to draw seawater into the tank. The drawn seawater and impurities are separated into layers. The mud and sludge are discharged downwards, while the water rises. During the rising process, the water can be filtered through a membrane tube. The filtered water finally flows into the interior of the enclosure through an overflow weir and is then discharged through a drain pipe. The integrated pretreatment device solves the problems of numerous pretreatment structures, large land area, and high cost.

[0027] 2. The present invention can also accelerate the discharge of mud and sludge and improve the cleanliness of the inside of the mud discharge pipe by using the mud scraping component and the auxiliary flushing component. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the overall structure of the present invention;

[0029] Figure 2 This is a cross-sectional view of the present invention;

[0030] Figure 3 This is a schematic diagram of the internal structure of the tank body of the present invention;

[0031] Figure 4 This is a schematic diagram of the conical bucket structure of the present invention;

[0032] Figure 5 This is a schematic diagram of the electric motor structure of the present invention;

[0033] Figure 6 For the present invention Figure 5 Enlarged view of point A in the middle;

[0034] Figure 7 This is a schematic diagram of the internal structure of the tee pipe and the sludge discharge pipe of the present invention;

[0035] Figure 8 This is a schematic diagram of the internal structure of the column of the present invention.

[0036] In the diagram: 1. Exhaust pipe; 2. Overflow weir; 3. Perforated plate; 4. Platform railing; 5. Tank body; 6. Inlet intermediate pipe; 7. Inlet water distributor; 8. Air distribution pipe; 9. Sludge discharge pipe; 10. Membrane pipe; 11. Gasket; 12. Enclosure frame; 13. Drain pipe; 14. Manhole; 15. Conical hopper; 16. T-joint; 17. High-pressure water inlet pipe; 18. Ring pipe; 19. Air outlet pipe; 20. Sludge scraper assembly; 21. Drive assembly; 22. Extension component; 23. Actuating component; 24. Electric motor; 25. Drive rod; 26. Worm gear; 27. Worm; 28. Arc-shaped scraper; 29. ​​Connecting rod; 30. Central shaft; 31. Spiral blade; 32. Column; 33. Receiving slot; 34. Block; 35. Gear missing; 36. Rack; 37. Slider; 38. Spring; 39. Actuating rod; 40. Turntable; 41. Arc-shaped lifting block; 42. Rotating shaft. Detailed Implementation

[0037] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0038] Example 1

[0039] Please see Figures 1-4 The gravity-type seawater desalination pretreatment device shown in the figure includes a tank 5 and a platform railing 4 fixedly installed on the outside of the tank 5. The bottom of the tank 5 is provided with a water distribution reaction mechanism, and a sludge discharge mechanism is provided below the water distribution reaction mechanism. The middle of the tank 5 is provided with an air washing and air distribution mechanism, and a nanoscale separation mechanism is provided above the air washing and air distribution mechanism. The top of the tank 5 is provided with a purified water discharge mechanism.

[0040] The water distribution reaction mechanism includes a conical hopper 15 fixedly installed on the lower inner side of the tank body 5, and a water inlet intermediate pipe 6 horizontally placed above the conical hopper 15. One end of the water inlet intermediate pipe 6 is fixedly inserted through the tank body 5, and the other end of the water inlet intermediate pipe 6 faces the center of the conical hopper 15. A water inlet distributor 7 is also fixedly installed at the end of the water inlet intermediate pipe 6 facing the conical hopper 15. The cone top of the conical hopper 15 is open. Two manholes 14 are also connected to the outer wall of the tank body 5, and the manholes 14 are located on the upper and lower sides of the conical hopper 15, respectively. Seawater that needs to be desalinated and pretreated is transported to the interior of the tank body 5 through the water inlet intermediate pipe 6 and the water inlet distributor 7 by a suction pump.

[0041] The sludge discharge mechanism includes a three-way pipe 16 fixedly connected to the bottom of the conical bucket 15. The other two ends of the three-way pipe 16 are respectively connected to a sludge discharge pipe 9 and a high-pressure water inlet pipe 17. The ends of the sludge discharge pipe 9 and the high-pressure water inlet pipe 17 away from the three-way pipe 16 extend to the outside of the tank body 5. The high-pressure water inlet pipe 17 can be connected to a high-pressure water source to flush the sludge inside the sludge discharge pipe 9.

[0042] The air washing and air distribution mechanism includes an annular pipe 18 located above the conical bucket 15, and the annular pipe 18 is installed coaxially with the conical bucket 15. An air distribution pipe 8 is fixedly connected to the outer side of the annular pipe 18, and the other end of the air distribution pipe 8 extends to the outside of the tank body 5. Several air outlet pipes 19 are fixedly connected to the upper and lower ends of the annular pipe 18 in a circularly equidistant manner. By designing several air outlet pipes 19 on the surface of the annular pipe 18, high-pressure gas can be uniformly used to wash and flush the membrane tube 10 and the conical bucket 15.

[0043] The nanoscale separation mechanism includes a porous plate 3 fixedly installed on the top of the tank 5, and several membrane tubes 10 are embedded inside the porous plate 3. The top of each membrane tube 10 is fixedly connected to the porous plate 3 through a gasket 11. An exhaust pipe 1 is also fixedly installed at the center of the porous plate 3. The two ends of the exhaust pipe 1 are located above and below the porous plate 3, respectively. The membrane tubes 10 are made of PTFE material. Since the surface of the PTFE membrane is very smooth, the particles attached to the surface of the membrane tubes 10 will automatically fall off and sink into the lower sludge discharge area when they grow to a certain size.

[0044] The water purification discharge mechanism includes an overflow weir 2 fixedly installed on the top of the tank 5, and the drainage height of the overflow weir 2 is greater than the height of the perforated plate 3 extending from the upper end of the membrane tube 10. A frame 12 is also fixedly fitted around the top of the tank 5, and the lower end of the frame 12 is lower than the lower end of the perforated plate 3. A drain pipe 13 is also fixedly installed at the bottom of the frame 12. The purified water will flow out through the overflow weir 2 and finally be discharged through the drain pipe 13.

[0045] A pretreatment process for a gravity-type seawater desalination pretreatment device includes the following steps:

[0046] S1. During the water intake stage, the seawater that needs to be desalinated is pumped through the intermediate water intake pipe 6 to the inside of the tank 5. As the seawater enters the tank 5, the silt and sand mixed in with it will be deposited on the upper part of the conical bucket 15, while the water will rise slowly step by step.

[0047] S2, during the sewage discharge stage, the conical hopper 15 guides the deposited silt and gravel into the interior of the three-way pipe 16, and finally discharges them through the sludge discharge pipe 9.

[0048] S3, Fine filtration stage: The rising seawater enters the interior of membrane tube 10. The membrane layer of membrane tube 10 can filter nanoscale dirt, allowing the filtered water to overflow through overflow weir 2 and finally be discharged through drain pipe 13.

[0049] Working principle: In this scheme, water intake, sludge removal, filtration, and drainage are integrated into a single tank 5, which effectively reduces the footprint of the seawater desalination pretreatment device and facilitates subsequent maintenance. During operation, the pretreatment device in this scheme uses a pump to deliver seawater into the tank 5 through the intermediate inlet pipe 6 and the inlet distributor 7. After the seawater enters the tank 5, the silt and sand mixed in will be deposited on the upper part of the conical hopper 15. The deposited silt and sand are guided by the conical hopper 15 and discharged through the three-way pipe 16 and the sludge discharge pipe 9. As the seawater is drawn up, it will be filtered through the membrane tube 10. The membrane tube 10 performs nano-level filtration of the seawater, which can isolate small particles. The filtered seawater overflows upward and finally overflows the overflow weir 2, flows into the enclosure 12, and is discharged through the drain pipe 13. This is the complete pretreatment process of the seawater pretreatment device in this scheme.

[0050] Backwashing is performed when the system's inlet and outlet pressure difference exceeds 0.05 MPa. Backwashing includes water backwashing and compressed air scrubbing. Water backwashing utilizes the permeate from other units, and its intensity is equal to the permeate output of one unit; therefore, this system requires at least two units per set. Water backwashing primarily removes smaller particles adhering to the membrane surface and larger particles captured in the middle. Compressed air scrubbing removes small particulate impurities and organic matter that are difficult to remove with water backwashing, adhering to the membrane micropores. Compressed air is introduced through the air distribution pipe 8 and finally ejected through the ring pipe 18 and the outlet pipe 19. The compressed air is sprayed onto the outer surfaces of the conical hopper 15 and the membrane tube 10. During air scrubbing, the membrane fibers rub and collide with each other, more effectively cleaning the adhering substances on the micropores. After backwashing is complete, the system can be put into the next cycle. If the system resistance still exceeds the standard after backwashing, chemical cleaning must be performed. This system can use strong acids, strong alkalis, or strong oxidants for cleaning. Almost all contaminants adhering to the membrane surface can be removed, ensuring that the membrane flux remains constant. After chemical cleaning, the waste liquid in the tank is discharged and replaced before the tank is put back into operation.

[0051] Example 2

[0052] Please see Figure 5 and Figure 6 This embodiment further illustrates Example 1, wherein a sludge scraping assembly 20 is provided between the conical bucket 15 and the three-way pipe 16, and a driving assembly 21 is provided on the outside of the sludge scraping assembly 20, and an auxiliary flushing assembly is provided inside the sludge discharge pipe 9.

[0053] The sludge scraping assembly 20 includes a central shaft 30 coaxially disposed inside the three-way pipe 16. The central shaft 30 rotatably passes through the three-way pipe 16, and the bottom of the central shaft 30 is rotatably embedded inside the tank body 5. The upper end face of the conical bucket 15 is provided with several arc-shaped sludge scraping blades 28 distributed circumferentially. A connecting rod 29 is fixedly connected between the end of the arc-shaped sludge scraping blade 28 near the central shaft 30 and the central shaft 30. A spiral blade 31 is also fixedly provided on the outer surface of the central shaft 30. The spiral blade 31 is generally shuttle-shaped. The end of the arc-shaped sludge scraping blade 28 away from the central shaft 30 has a large bend angle. During the sludge scraping process, the sludge will flow back and slide down the conical bucket 15.

[0054] The drive assembly 21 includes a worm gear 26 fixedly sleeved at the bottom of the central shaft 30, and a worm 27 meshing with the outside of the worm gear 26. An electric motor 24 is fixedly installed on the outside of the tank body 5, and a drive rod 25 is provided at the output end of the electric motor 24. The drive rod 25 rotates through the tank body 5, and the worm 27 is fixedly sleeved on the outside of the drive rod 25. The electric motor 24 drives the worm 27 to rotate, thereby causing the worm gear 26 to rotate with the central shaft 30.

[0055] In this embodiment: considering that the silt and sand mixed in the seawater are easy to adhere to the upper wall of the conical bucket 15, and the long-term accumulation will make it impossible to clean the inside of the tank 5 during the backwashing process. Therefore, in this solution, when the pretreatment device is started, the motor 24 is also started, and the worm gear 27 drives the worm wheel 26 to rotate, so that the central shaft 30 slides along the upper wall of the conical bucket 15 with the arc-shaped scraper 28.

[0056] After the pumped seawater and mixed silt impurities are transported to the top of the conical bucket 15, the transport speed is not very aggressive. This is because the silt needs to settle down quickly so that the seawater can rise in layers. The silt accumulates slowly. Therefore, by scraping the silt with the curved end of the arc-shaped scraper 28, the silt impurities can be guided to move faster and prevent the silt from sticking for a long time, which would make it impossible to clean it properly later.

[0057] Among them, the shuttle-shaped spiral blades 31 on the surface of the central shaft 30 can also feed the sludge that enters the three-way pipe 16, allowing the sludge to quickly enter the sludge discharge pipe 9 for discharge.

[0058] Example 3

[0059] Please see Figure 7 and Figure 8 This embodiment further illustrates other embodiments: the auxiliary flushing assembly includes a plurality of columns 32 axially fixed inside the sludge discharge pipe 9, each column 32 having an extension component 22 inside, and a triggering component 23 at the lower end of the column 32.

[0060] The extension component 22 includes a receiving slot 33 opened inside the column 32, and two symmetrically distributed blocking blocks 34 are placed inside the receiving slot 33. Each blocking block 34 has a missing gear 35 fixedly installed at its bottom, and the missing gear 35 is hinged to the column 32. A rack 36 is meshed between the two missing gears 35. A slider 37 is fixedly installed at the bottom of the rack 36 and is slidably embedded inside the column 32. A spring 38 is provided between the upper part of the slider 37 and the column 32, and an actuating rod 39 is fixedly installed at the lower part of the slider 37 and slides through the column 32. When the rack 36 moves upward, the two blocking blocks 34 can be opened simultaneously through the meshing of the rack 36 and the missing gear 35.

[0061] The actuating component 23 includes a turntable 40 located below each actuating rod 39. Each turntable 40 and the actuating rod 39 are eccentrically arranged. An arc-shaped lifting block 41 is fixedly installed at the upper end of each turntable 40, and a rotating shaft 42 is fixedly installed at the bottom of the turntable 40 and is rotatably embedded inside the tank body 5. A synchronous gear is fixedly sleeved on the outer surface of several rotating shafts 42 and the central shaft 30, and a synchronous toothed belt is provided for transmission among several synchronous gears. The rotation of the central shaft 30 can drive the rotating shafts 42 and the turntable 40 to rotate through the synchronous gears and the synchronous toothed belt.

[0062] In this embodiment: When flushing the mud and sludge inside the sludge discharge pipe 9 through the high-pressure water inlet pipe 17, since the water inlet of the high-pressure water inlet pipe 17 is direct, if some hard sand and gravel particles are adhered to the surface of the sludge discharge pipe 9, they cannot be cleaned. Therefore, in this solution, when flushing the sludge discharge pipe 9 with high-pressure water, the motor 24 can activate the rotating shaft 42 to make it rotate the turntable 40. During the rotation, the arc-shaped lifting block 41 can continuously push the trigger rod 39 upward. During the upward movement of the rack 36, through the meshing with the gear 35, the blocking block 34 can be deployed. That is, during the high-pressure water flow, the blocking block 34 can be deployed intermittently. When deployed, the obstruction of the high-pressure water flow will cause the high-pressure water flow flushing the inside of the sludge discharge pipe 9 to be separated and sprayed. The multi-angle dispersion and spraying of the water flow can effectively clean the impurities on the inner wall of the sludge discharge pipe 9 and improve the flushing and cleaning effect.

[0063] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0064] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A gravity-type seawater desalination pretreatment device, characterized in that: Includes a tank (5) and a platform railing (4) fixedly installed on the outside of the tank (5). The bottom of the tank (5) is provided with a water distribution reaction mechanism, and a sludge discharge mechanism is provided below the water distribution reaction mechanism. The middle part of the tank (5) is provided with an air washing and air distribution mechanism, and a nano-level separation mechanism is provided above the air washing and air distribution mechanism. The top of the tank (5) is provided with a clean water discharge mechanism. The water distribution reaction mechanism includes a conical bucket (15) fixedly installed on the lower inner side of the tank (5), and a water inlet intermediate pipe (6) is horizontally placed above the conical bucket (15). One end of the water inlet intermediate pipe (6) is fixedly inserted through the tank (5), and the other end of the water inlet intermediate pipe (6) faces the center of the conical bucket (15). A water inlet distributor (7) is also fixedly installed at the end of the water inlet intermediate pipe (6) facing the conical bucket (15). The cone top of the conical bucket (15) is open. Two manholes (14) are also connected to the outer wall of the tank (5), and the manholes (14) are located on the upper and lower sides of the conical bucket (15), respectively. The sludge discharge mechanism includes a three-way pipe (16) fixedly connected to the bottom end of the conical bucket (15). The other two ends of the three-way pipe (16) are respectively connected to a sludge discharge pipe (9) and a high-pressure water inlet pipe (17). The ends of the sludge discharge pipe (9) and the high-pressure water inlet pipe (17) away from the three-way pipe (16) both extend to the outside of the tank body (5). A sludge scraping assembly (20) is provided between the conical bucket (15) and the three-way pipe (16), and a drive assembly (21) is provided on the outside of the sludge scraping assembly (20), and an auxiliary flushing assembly is provided inside the sludge discharge pipe (9); The sludge scraping assembly (20) includes a central shaft (30) coaxially disposed inside the three-way pipe (16). The central shaft (30) rotatably passes through the three-way pipe (16), and the bottom of the central shaft (30) is rotatably embedded inside the tank body (5). The upper end face of the conical bucket (15) is provided with a number of arc-shaped sludge scraping blades (28) distributed equidistantly around the circumference. A connecting rod (29) is fixedly connected between the end of the arc-shaped sludge scraping blade (28) near the central shaft (30) and the central shaft (30). A spiral blade (31) is also fixedly disposed on the outer surface of the central shaft (30), and the spiral blade (31) is spindle-shaped in whole. The drive assembly (21) includes a worm gear (26) fixedly sleeved at the bottom of the central shaft (30), and a worm (27) is meshed on the outside of the worm gear (26). An electric motor (24) is fixedly installed on the outside of the tank (5), and a drive rod (25) is provided at the output end of the electric motor (24). The drive rod (25) rotates through the tank (5), and the worm (27) is fixedly sleeved on the outside of the drive rod (25). The auxiliary flushing assembly includes several columns (32) fixed axially inside the sludge discharge pipe (9). Each column (32) has an extension component (22) inside and a trigger component (23) at the lower end of the column (32). The extension component (22) includes a receiving slot (33) opened inside the column (32), and two symmetrically distributed blocking blocks (34) are placed inside the receiving slot (33). A missing gear (35) is fixedly installed at the bottom of each blocking block (34), and the missing gear (35) is hinged to the column (32). A rack (36) is meshed between the two missing gears (35). A slider (37) is fixedly installed at the bottom of the rack (36) and slides inside the column (32). A spring (38) is provided between the upper part of the slider (37) and the column (32), and an actuating rod (39) that slides through the column (32) is fixedly installed at the lower part of the slider (37). The triggering component (23) includes a turntable (40) located below each triggering rod (39). Each turntable (40) and the triggering rod (39) are eccentrically arranged. An arc-shaped lifting block (41) is fixedly installed at the upper end of each turntable (40). A rotating shaft (42) is fixedly installed at the bottom of the turntable (40) and is rotatably embedded inside the tank body (5). A synchronous gear is fixedly sleeved on the outer surface of several rotating shafts (42) and the central shaft (30). A synchronous toothed belt is provided for the common transmission between several synchronous gears.

2. The gravity-type seawater desalination pretreatment device according to claim 1, characterized in that: The air washing and air distribution mechanism includes an annular pipe (18) located above the conical bucket (15), and the annular pipe (18) is installed coaxially with the conical bucket (15). An air distribution pipe (8) is fixedly connected to the outer side of the annular pipe (18), and the other end of the air distribution pipe (8) extends to the outside of the tank body (5). Several air outlet pipes (19) are fixedly connected to the upper and lower ends of the annular pipe (18) in a circumferentially equidistant manner.

3. The gravity-type seawater desalination pretreatment device according to claim 2, characterized in that: The nanoscale separation mechanism includes a porous plate (3) fixedly installed on the top of the tank (5), and a number of membrane tubes (10) are embedded inside the porous plate (3). The top of each membrane tube (10) is fixedly connected to the porous plate (3) through a gasket (11). An exhaust pipe (1) is also fixedly installed at the center of the porous plate (3), and the two ends of the exhaust pipe (1) are located above and below the porous plate (3) respectively.

4. The gravity-type seawater desalination pretreatment device according to claim 3, characterized in that: The water purification discharge mechanism includes an overflow weir (2) fixedly installed on the top of the tank (5), and the drainage height of the overflow weir (2) is greater than the height of the upper end of the membrane tube (10) extending out of the perforated plate (3). A frame (12) is also fixedly sleeved on the top periphery of the tank (5), and the lower end face of the frame (12) is lower than the lower end face of the perforated plate (3). A drain pipe (13) is also fixedly installed at the bottom of the frame (12).

5. The pretreatment process of a gravity-type seawater desalination pretreatment device according to claim 1, characterized in that: Includes the following steps: S1. During the water intake stage, the seawater that needs to be desalinated is pumped through the water intake intermediate pipe (6) to the inside of the tank (5). During the process of the seawater entering the tank (5), the silt and sand mixed in it will be deposited on the upper part of the conical bucket (15), while the water will rise slowly step by step. S2, during the sewage discharge stage, the conical bucket (15) guides the deposited silt and gravel into the interior of the three-way pipe (16), and finally discharges them through the sludge discharge pipe (9); S3, Fine filtration stage: The rising seawater will enter the interior of the membrane tube (10). The membrane layer of the membrane tube (10) can filter nanoscale dirt, so that the filtered water overflows through the overflow weir (2) and is finally discharged through the drain pipe (13).

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