A pneumatic lifting system and a pneumatic lifting method for seabed ore.

Abstract

This invention discloses a pneumatic lifting system and a method for pneumatically lifting seabed ore. The pneumatic lifting system includes a lift pipe and an air compressor. The compressed air outlet of the air compressor is connected to the lift pipe via a main air supply pipe. A back pressure cylinder is connected to the outlet of the lift pipe. When the lift pipe discharges a solid-gas-liquid three-phase fluid into the back pressure cylinder, the back pressure cylinder maintains a first pressure, which is positive. The back pressure cylinder is provided with a gas outlet, and a first valve is provided at the gas outlet to adjust the magnitude of the first pressure within the back pressure cylinder to control the flow velocity of the solid-gas-liquid three-phase fluid in the lift pipe. The pneumatic lifting system and method of this invention, by adding a back pressure cylinder at the outlet of the lift pipe, reduces the expansion of the compressed air and can significantly reduce the flow velocity of the solid-gas-liquid three-phase fluid at the lift pipe outlet.

Description

Technical Field

[0001] This invention belongs to the field of deep-sea mining technology, and particularly relates to a pneumatic lifting system and method for transporting minerals. Background Technology

[0002] Mineral resources, as an important natural resource, are a crucial material foundation for human society's production and development. In deep-sea mining systems, pneumatic hoisting and hydraulic hoisting are widely recognized as promising methods for ore hoisting with industrial applications. Compared to hydraulic hoisting, pneumatic hoisting, with its air compressor installed on the mining vessel and no moving parts underwater, offers advantages such as convenient operation and maintenance, and a simple and reliable process.

[0003] In deep-sea mining pneumatic lifting systems, the lower part of the air inlet exhibits a solid-liquid two-phase flow, while the upper part exhibits a solid-liquid-gas three-phase flow. The air inlet depth is typically between 2000-2500 meters, where the seawater temperature is approximately 2-3°C. Under such high pressure and low temperature conditions, the compression, expansion, and dissolution of air in seawater become particularly pronounced. During the three-phase flow ascent, as the pressure gradually decreases, the rising bubbles continuously expand, leading to a continuous increase in the flow velocity within the pipe, especially near the sea surface, where the three-phase flow velocity becomes very high. Based on existing data, the air velocity at the outlet of the lift pipe in deep-sea mining pneumatic lifting systems is approximately 30-50 m / s. Excessively high velocities accelerate pipe and equipment wear, severely fragment and pulverize nodules, negatively impacting pipe service life and slurry settling on board, and increasing lifting energy consumption and costs.

[0004] Therefore, measures must be taken to reduce the three-phase flow velocity within the lift pipe. Existing technologies employ a stepped reducer pipe in the upper part of the pneumatic lifting system to increase the pipe diameter. However, this measure has drawbacks: larger pipe diameters increase pipeline manufacturing costs, require more deck space on the ship, and increase the difficulty of deployment, retrieval, and maintenance. Therefore, it is necessary to propose a new measure to reduce the three-phase flow velocity within the lift pipe of a pneumatic lifting system. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to overcome the deficiencies and defects mentioned in the background art above, and to provide a pneumatic lifting system with a back pressure device for reducing the three-phase fluid velocity at the outlet of the riser pipe and a pneumatic lifting method for seabed ore.

[0006] To solve the above-mentioned technical problems, the technical solution proposed by this invention is as follows:

[0007] A pneumatic lifting system with a back pressure device includes a lifting pipe and an air compressor. The compressed air outlet of the air compressor is connected to the lifting pipe through a main air supply pipe. The outlet of the lifting pipe is connected to a back pressure cylinder. When the lifting pipe discharges a solid-gas-liquid three-phase fluid into the back pressure cylinder, the back pressure cylinder maintains a first pressure, which is a positive pressure. The back pressure cylinder is provided with a gas outlet. A first valve is provided at the gas outlet to adjust the magnitude of the first pressure in the back pressure cylinder to control the flow rate of the solid-gas-liquid three-phase fluid in the lifting pipe.

[0008] In the aforementioned pneumatic lifting system, preferably, one end of the first valve is connected to the gas outlet, and the other end of the first valve is connected to the inlet of a booster compressor via a first gas supply pipe. The outlet of the booster compressor is connected to the main gas supply pipe via a second gas supply pipe, and a one-way valve is provided on the second gas supply pipe. This invention uses the first valve and the first gas supply pipe to deliver pressurized air to the booster compressor, and then sends it to the main gas supply pipe via the second gas supply pipe, achieving the recycling of pressurized air. The air compressor is used to supplement the compressed gas, further improving the efficiency of the air compressor and the pneumatic lifting system. Simultaneously, the reuse of compressed air avoids the discharge of air containing fine particles with polymetallic nodules, preventing environmental impact on mining vessels. The aforementioned one-way valve allows only unidirectional gas flow, permitting air to be delivered from the second gas supply pipe to the main gas supply pipe only, preventing reverse flow.

[0009] In the aforementioned pneumatic lifting system, preferably, one end of the first valve is connected to the gas outlet via a T-junction, and the other end of the T-junction is provided with a second valve for connecting the back pressure cylinder to the outside (or atmosphere). The opening or closing of the second valve can be used to control whether the back pressure cylinder is connected to the outside, facilitating the regulation of the pressure within the back pressure cylinder.

[0010] In the aforementioned pneumatic booster system, preferably, the first gas delivery pipe is equipped with a cleaning device for cleaning the gas. The cleaning device includes a refrigerated dryer and a filter in sequence according to the gas flow direction. Using a refrigerated dryer and a filter can clean the air discharged from the back pressure cylinder, preventing any impact on the booster compressor.

[0011] In the aforementioned pneumatic lifting system, preferably, the back pressure cylinder is equipped with a buffer to cushion the force of the solid-gas-liquid three-phase fluid discharged from the outlet of the lifting pipe. The buffer can buffer the force of the solid-gas-liquid three-phase fluid discharged from the lifting pipe, reduce the breakage rate of solid particles, and facilitate the separation of solid and liquid phases by sedimentation.

[0012] In the aforementioned pneumatic lifting system, preferably, the outlet of the lifting pipe is located in the middle of the back pressure cylinder, and the buffer is arranged opposite to the outlet of the lifting pipe. The buffer includes a metal disc, wear-resistant rubber, a buffer spring, a connecting rod, and a guide cylinder. The wear-resistant rubber is disposed on the surface of the metal disc, facing the outlet of the lifting pipe. The center of the metal disc and the center of the lifting pipe outlet are on the same axis. The guide cylinder is located on the outer wall of the back pressure cylinder. One end of the metal disc is connected to one end of the connecting rod, and the other end of the connecting rod is movably located in the guide cylinder. The buffer spring is sleeved on the connecting rod and is engaged between the metal disc and the inner wall of the back pressure cylinder. The solid polymetallic nodules in the solid-gas-liquid three-phase fluid are coarse-grained ore particles several centimeters in diameter. Severe crushing and pulverization of these polymetallic nodule particles affects the settling of the slurry in the storage tank of the mining vessel, and the discharge of fine particles will increase metal loss. In this invention, the buffer with the above-described structure allows the two-phase mixture of seawater and polymetallic nodules to act on a metal disc with wear-resistant rubber when the three-phase mixture of compressed air, seawater, and polymetallic nodules enters the back pressure cylinder from the riser outlet. Under the action of the buffer spring, the connecting rod reciprocates within the guide cylinder, reducing the impact force of the polymetallic nodule particles and minimizing their breakage and pulverization.

[0013] In the aforementioned pneumatic lifting system, preferably, the bottom outlet of the back pressure cylinder is connected to a storage tank via a connecting pipe. The diameter of the connecting pipe is 1.5-2 times the diameter of the lifting pipe. A seawater discharge pipe is connected to the connecting pipe via a third valve. During the lifting of seabed ore, the solid and liquid phases within the back pressure cylinder will enter the storage tank through the connecting pipe for further sedimentation and separation. Upon completion of the lifting operation, the third valve is opened, allowing the seawater in the back pressure cylinder and storage tank to be discharged through the seawater discharge pipe. The diameter of the bottom outlet pipe of the back pressure cylinder (i.e., the connecting pipe) is larger than the diameter of the lifting pipe, which facilitates the transfer of the solid and liquid phases within the back pressure cylinder. Generally, the diameter of the connecting pipe is 1.5-2 times the diameter of the lifting pipe. For example, if the diameter of the lifting pipe is 200 mm, the diameter of the connecting pipe is approximately 300-400 mm.

[0014] In the above-mentioned pneumatic lifting system, preferably, the top overflow outlet of the storage tank is connected to a secondary sedimentation tank, the top of the secondary sedimentation tank is provided with an overflow water pipe, the storage tank is connected to a seawater delivery pipe, the inlet end of the seawater delivery pipe is located below the sea surface, and the end is provided with a submersible pump.

[0015] In the above-mentioned pneumatic lifting system, preferably, when the lifting pipe discharges a solid-gas-liquid three-phase fluid into the back pressure cylinder, the back pressure cylinder is equipped with a liquid seal, and the liquid level in the back pressure cylinder is kept at the same level as the liquid level in the storage tank.

[0016] The solid and liquid phases entering the storage tank from the back pressure cylinder undergo sedimentation and separation. Polymetallic nodules settle freely to the bottom of the storage tank, while seawater containing marine mud and fine-particle nodules overflows into a secondary sedimentation tank for secondary sedimentation. The seawater after secondary sedimentation is discharged into the sea through an overflow pipe. Before the seabed minerals are lifted, seawater is supplied to both the storage tank and the back pressure cylinder through seawater delivery pipes to maintain them at the same liquid level. During the three-phase flow transportation process, the liquid level in the back pressure cylinder and the liquid level in the storage tank remain at the same height.

[0017] As a general technical concept, the present invention also provides a method for pneumatic lifting of seabed ore using the above-mentioned pneumatic lifting system, comprising the following steps:

[0018] S1: Connect the back pressure cylinder to the outside world and add seawater into the back pressure cylinder;

[0019] S2: Close the connection between the back pressure cylinder and the outside world, start the air compressor, and the compressed air compressed by the air compressor is delivered to the riser pipe through the air supply main. Due to the injection of compressed air, the seabed ore is sucked in from the bottom of the riser pipe and lifted to the outlet of the riser pipe, and discharged into the back pressure cylinder as a solid-gas-liquid three-phase fluid. During the lifting process, the back pressure cylinder is kept under positive pressure, and the flow rate of the solid-gas-liquid three-phase fluid in the riser pipe is adjusted by the opening and closing degree of the first valve.

[0020] S3: After the seabed ore is lifted, turn off the air compressor and connect the back pressure cylinder to the outside to release the internal pressure.

[0021] The working process of the pneumatic lifting system of the present invention is roughly as follows:

[0022] A three-phase mixture of compressed air, seawater, and polymetallic nodules enters the back pressure cylinder through the riser outlet. The compressed air in the three-phase mixture is separated from the seawater and polymetallic nodules in the back pressure cylinder. The separated compressed air is recycled through the first valve at the upper part of the back pressure cylinder. The separated seawater and polymetallic nodules freely settle into the connecting pipe at the lower part of the back pressure cylinder and are transported to the storage tank on the mining vessel through the connecting pipe. The polymetallic nodules freely settle to the bottom of the storage tank, and the seawater flows into the secondary sedimentation tank through the storage tank for sedimentation. The settled seawater is discharged underwater through the overflow pipe.

[0023] The working principle of the pneumatic lifting system of the present invention is roughly as follows:

[0024] Compressed air is injected into the riser at an appropriate seawater depth. Because the density of the solid-gas-liquid three-phase mixture formed by the compressed air, seawater, and polymetallic nodules in the pipe is less than the density of the seawater outside the riser, a density difference is created inside and outside the pipe, forming an upwelling flow of seawater within the pipe, lifting the polymetallic nodules to the sea surface. Below the air inlet, the riser experiences a solid-liquid two-phase flow, with the pressure inside the pipe lower than the pressure outside; the polymetallic nodules are lifted by the potential energy of the seawater. Above the air inlet, the riser experiences a solid-liquid-gas three-phase flow, with the pressure inside the pipe higher than the pressure outside; the polymetallic nodules are lifted by the pressure of the compressed air discharged from the air compressor.

[0025] According to the working principle of pneumatic pipeline lifting, the pressure inside the pipe below the air inlet is lower than the external pressure, while the pressure inside the pipe above the air inlet is higher than the external pressure. The lifting pipe outlet maintains a certain internal pressure. The three-phase mixture under this internal pressure separates within the back pressure cylinder, where the separated seawater and polymetallic nodules form a liquid surface. If the second valve is opened and the first valve is closed, the separated compressed air is discharged into the atmosphere, and positive pressure cannot be formed within the back pressure cylinder, thus failing to reduce the three-phase flow velocity within the lifting pipe. When the second valve is closed and the first valve is opened, compressed air is discharged into the first air delivery pipe, creating positive pressure within the back pressure cylinder, which reduces the three-phase flow velocity within the lifting pipe. Adjusting the opening and closing degree of the first valve can further regulate the flow velocity of the three-phase flow in the lifting pipe. Specifically, reducing the opening degree of the first valve increases the positive pressure in the back pressure cylinder, which can reduce the flow velocity of the three-phase flow in the lifting pipe. However, if the flow velocity of the three-phase flow in the lifting pipe decreases to the critical velocity, the pneumatic lifting system will not work properly, the density and pressure loss of the three-phase mixture will increase, and pipe blockage may occur.

[0026] Compared with the prior art, the advantages of the present invention are as follows:

[0027] 1. The pneumatic lifting system and method with back pressure device of the present invention adds a back pressure cylinder at the outlet of the lifting pipe of the pneumatic lifting system. This reduces the expansion of compressed air, which can significantly reduce the flow velocity of the solid-gas-liquid three-phase fluid at the outlet of the lifting pipe, reduce frictional losses within the lifting pipe, prevent excessive crushing of mineral particles, extend the service life of the lifting pipe, and improve the efficiency of the pneumatic lifting system. Simultaneously, by setting a first valve on the back pressure cylinder, the opening and closing degree of the first valve can be used to adjust the first pressure within the back pressure cylinder, which can indirectly regulate the flow velocity of the solid-gas-liquid three-phase fluid within the lifting pipe, thereby meeting the requirements of various conveying conditions.

[0028] 2. The pneumatic lifting system and method with back pressure device of this invention is an energy-saving device with simple structure, low cost, easy operation and maintenance. It can fully meet the technical requirements of pneumatic lifting systems for deep-sea mining. The successful research and development of this back pressure device can fill the gap in my country's pneumatic lifting systems for deep-sea mining. On the one hand, it can be applied to pneumatic lifting systems for deep-sea mining; on the other hand, it can also be applied to pneumatic coal mining and land-based underwater mining, promoting the rapid development of my country's deep-sea mining technology and enabling my country's development and research technology of pneumatic lifting systems for deep-sea mining to reach the international advanced level. Attached Figure Description

[0029] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0030] Figure 1 This is a schematic diagram of the pneumatic lifting system with back pressure device of the present invention.

[0031] Figure 2 This is a schematic diagram of the buffer structure in the pneumatic lifting system with back pressure device of the present invention.

[0032] Legend

[0033] 1. Lift pipe; 2. Air inlet; 3. Seawater outlet pipe; 4. Overflow pipe; 5. Submersible pump; 6. Seawater delivery pipe; 7. Secondary sedimentation tank; 8. Storage tank; 9. Third valve; 10. Connecting pipe; 11. Buffer spring; 12. Connecting rod; 13. Guide cylinder; 14. Metal disc; 15. Wear-resistant rubber; 16. Back pressure cylinder; 17. Second valve; 18. T-junction; 19. First valve; 20. Refrigerated dryer; 21. Filter; 22. First air supply pipe; 23. Booster; 24. Second air supply pipe; 25. Check valve; 26. Main air supply pipe; 29. ​​Air compressor; 30. Mining vessel. Detailed Implementation

[0034] To facilitate understanding of the present invention, the present invention will be described more fully and in detail below with reference to the accompanying drawings and preferred embodiments, but the scope of protection of the present invention is not limited to the following specific embodiments.

[0035] It should be noted that when a component is described as being "fixed to, attached to, connected to or connected to" another component, it can be directly fixed to, attached to, connected to or connected to the other component, or it can be indirectly fixed to, attached to, connected to or connected to the other component through other intermediate connectors.

[0036] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.

[0037] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0038] Example:

[0039] like Figure 1 As shown, the pneumatic lifting system with back pressure device in this embodiment includes a lifting pipe 1 and an air compressor 29. The compressed air outlet of the air compressor 29 is connected to the lifting pipe 1 through a gas supply main pipe 26. The outlet of the lifting pipe 1 is connected to a back pressure cylinder 16. When the lifting pipe 1 discharges a solid-gas-liquid three-phase fluid into the back pressure cylinder 16, the back pressure cylinder 16 is maintained at a first pressure, which is a positive pressure. The back pressure cylinder 16 is provided with a gas outlet. A first valve 19 (self-controlled valve) is provided at the gas outlet to adjust the magnitude of the first pressure in the back pressure cylinder 16 to control the flow rate of the solid-gas-liquid three-phase fluid in the lifting pipe 1.

[0040] In this embodiment, one end of the first valve 19 is connected to the gas outlet, and the other end of the first valve 19 is connected to the inlet of a booster 23 through the first gas supply pipe 22. The outlet of the booster 23 is connected to the gas supply main pipe 26 through the second gas supply pipe 24. A one-way valve 25 is provided on the second gas supply pipe 24.

[0041] In this embodiment, one end of the first valve 19 is connected to the gas outlet through a three-way pipe 18, and the other end of the three-way pipe 18 is provided with a second valve 17 (self-controlled valve) for connecting the back pressure cylinder 16 with the outside world.

[0042] In this embodiment, the first gas supply pipe 22 is provided with a cleaning device for cleaning gas, which includes a refrigerated dryer 20 and a filter 21 in sequence according to the gas flow direction.

[0043] In this embodiment, the back pressure cylinder 16 is equipped with a buffer to cushion the force of the solid-gas-liquid three-phase fluid discharged from the outlet of the riser pipe 1. Specifically, as shown... Figure 2As shown, the outlet of the riser pipe 1 is located in the middle of the back pressure cylinder 16, and the buffer and the outlet of the riser pipe 1 are arranged opposite each other. The buffer includes a metal disc 14, a wear-resistant rubber 15, a buffer spring 11, a connecting rod 12 and a guide cylinder 13. The wear-resistant rubber 15 is provided on the surface of the metal disc 14, facing the outlet of the riser pipe 1. The guide cylinder 13 is located on the outer wall of the back pressure cylinder 16. One end of the metal disc 14 and the connecting rod 12 are connected, and the other end of the connecting rod 12 is movably located in the guide cylinder 13. The buffer spring 11 is sleeved on the connecting rod 12 and is locked between the metal disc 14 and the inner wall of the back pressure cylinder 16.

[0044] In this embodiment, the bottom outlet of the back pressure cylinder 16 is connected to a storage tank 8 via a connecting pipe 10. The diameter of the connecting pipe 10 is 1.5-2 times the diameter of the riser pipe 1. A seawater discharge pipe 3 is connected to the connecting pipe 10 via a third valve 9 (automatic valve). The top overflow outlet of the storage tank 8 is connected to a secondary sedimentation tank 7. An overflow water pipe 4 is provided at the top of the secondary sedimentation tank 7. A seawater delivery pipe 6 is connected to the storage tank 8. The inlet end of the seawater delivery pipe 6 is below the sea surface, and a submersible pump 5 is provided at the end.

[0045] In this embodiment, when the riser 1 discharges the solid-gas-liquid three-phase fluid into the back pressure cylinder 16, a liquid seal is provided inside the back pressure cylinder 16, and the liquid level in the back pressure cylinder 16 and the liquid level in the storage tank 8 are kept the same.

[0046] In this embodiment, the volume of the back pressure cylinder 16 is determined by the flow rate of the three-phase flow. The cylinder volume increases with the increase of the three-phase flow rate. Generally, for example, if the slurry flow rate is 360 m³ / s... 3 / h, three-phase flow conveying time is about 15-20s, cylinder volume is about 1.5-2m³. 3 This volume is sufficient to meet the requirements for air separation and free settling of polymetallic nodules. The positional relationship between the riser 1 outlet and the back pressure cylinder 16, as well as the positions of the gas and solid-liquid outlets of the back pressure cylinder 16, are subject to certain requirements to ensure the separation effect of compressed air with seawater polymetallic nodules within the back pressure cylinder 16. If the inlet positions of the three-phase fluid, the outlet positions of the compressed air and solid-liquid fluids, and the diameter of the connecting pipe 10 are not arranged reasonably, the separation effect will be affected. In this embodiment, the outlet of the riser pipe 1 is located in the middle of the back pressure cylinder 16 and is fixed to the outer surface of the back pressure cylinder 16. The outlet of the compressed air is located at the top of the back pressure cylinder 16 and is fixed to the outer top surface of the back pressure cylinder 16. The diameter of the connecting pipe 10 is larger than the diameter of the riser pipe 1. The connecting pipe 10 is located at the bottom of the back pressure cylinder 16 and is fixed to the outer bottom surface of the back pressure cylinder 16. Generally, the diameter of the connecting pipe 10 is 1.5-2 times the diameter of the riser pipe 1. For example, if the diameter of the riser pipe 1 is 200mm, the diameter of the connecting pipe 10 is about 300-400mm.

[0047] This embodiment utilizes the above-mentioned pneumatic lifting system for pneumatic lifting of seabed ore, including the following steps:

[0048] S1: Connect the back pressure cylinder 16 to the outside world and add seawater into the back pressure cylinder 16;

[0049] S2: Close the connection between the back pressure cylinder 16 and the outside world, start the air compressor 29, and the compressed air compressed by the air compressor 29 is delivered to the riser pipe 1 through the air supply main pipe 26. Due to the injection of compressed air, the seabed ore is sucked in from the bottom of the riser pipe 1 and lifted to the outlet of the riser pipe 1, and discharged into the back pressure cylinder 16 as a solid-gas-liquid three-phase fluid. During the lifting process, the back pressure cylinder 16 maintains positive pressure, and the flow rate of the solid-gas-liquid three-phase fluid in the riser pipe 1 is adjusted by the opening and closing degree of the first valve 19.

[0050] S3: After the seabed ore is lifted, turn off the air compressor 29 and connect the back pressure cylinder 16 to the outside to release the internal pressure.

[0051] More specifically, methods to enhance strength may include the following steps:

[0052] Before lifting, close the third valve 9, open the first valve 19 and the second valve 17, start the submersible pump 5, and transport seawater to the storage tank 8 through the seawater delivery pipe 6, and then flow into the back pressure cylinder 16 through the connecting pipe 10. When the liquid level in the back pressure cylinder 16 is at the same height as the liquid level in the storage tank 8, the seawater in the storage tank 8 flows into the secondary sedimentation tank 7 and is discharged into the sea through the overflow pipe 4. At this time, stop the submersible pump 5 and close the second valve 17.

[0053] During the lifting process, the air compressor 29 is activated. Atmospheric air enters the air compressor 29 through its inlet and is compressed. The compressed air is then transported to the air injection port 2 via the main air supply pipe 26, and then to the outlet of the lift pipe 1. The compressed air and the seawater in the lift pipe 1 form an upwelling flow. The bubbles in the upwelling flow continuously expand, and the flow velocity in the lift pipe 1 continuously increases, thus creating a density difference between the inside and outside of the pipe. This draws the polymetallic nodules from the seabed from the bottom of the lift pipe 1 and lifts them to the outlet. The solid and liquid phases of the three-phase mixture at the outlet of the lift pipe 1 are separated from the compressed air in the back pressure cylinder 16. The separated solid and liquid phases directly impact the surface of the metal disc 14 bonded with wear-resistant rubber 15. Under the action of the buffer spring 11, the seawater and polymetallic nodules freely settle to the lower part of the back pressure cylinder 16 and are transported to the storage tank 8 through the connecting pipe 10. The polymetallic nodules freely settle in the storage tank 8, while the seawater flows into the secondary sedimentation tank 7. The settled seawater is then discharged into the sea through the overflow pipe 4. The separated compressed air, located at the top of the back pressure cylinder 16, is transported to the booster compressor 23 via a three-way pipe 18, a first valve 19, a refrigerated dryer 20, a filter 21, and a first air delivery pipe 22. Under the action of the booster compressor 23, the compressed air undergoes a secondary circulation and pressurization, and is then transported to the air injection port 2 via a second air delivery pipe 24, a one-way valve 25, and a main air delivery pipe 26, thus achieving secondary utilization of the compressed air. Furthermore, when the booster compressor 23 is operating, the air compressor 29 automatically stops working; when there is air volume loss in the pipelines and equipment during the air delivery process, the air compressor 29 automatically starts to meet the air volume requirements of the pneumatic lifting system. In addition, the flow rate of the three-phase fluid at the outlet of the lift pipe 1 can be controlled by adjusting the opening of the first valve 19 according to the technical requirements of the pneumatic lifting system.

[0054] When the lifting operation is complete, the supply of polymetallic nodules to the bottom of the riser pipe 1 is stopped. When seawater is discharged from the outlet of the riser pipe 1, the booster compressor 23 and the air compressor 29 are shut off in sequence, and the second valve 17 is opened to discharge the remaining compressed air in the riser pipe 1 and the back pressure cylinder 16. After a period of time, the third valve 9 is opened, and the seawater in the back pressure cylinder 16 and the storage tank 8 is discharged into the sea through the seawater discharge pipe 3 to collect the polymetallic nodules.

[0055] The entire process of starting, operating, and stopping each device and valve in the above steps is monitored, measured, and controlled by the remote monitoring and control station on the mining vessel 30. The working status of the equipment in each starting step and process is clearly displayed on the computer screen. If a problem occurs during the start-up or operation, an alarm signal will be issued.

[0056] The pneumatic lifting system with back pressure device in this embodiment, through the setting of back pressure cylinder 16 and first valve 19, can adjust the flow rate of the three-phase fluid at the outlet of lifting pipe 1, reduce friction loss in lifting pipe 1, prevent excessive crushing of mineral particles, extend the service life of lifting pipe 1, and improve the efficiency of the pneumatic lifting system. Simultaneously, the first pressure in back pressure cylinder 16 can be adjusted by the opening and closing degree of first valve 19, which can indirectly adjust the flow rate of the solid-gas-liquid three-phase fluid in lifting pipe 1, thereby meeting the requirements of various conveying conditions. At the same time, the large amount of compressed air discharged from back pressure cylinder 16 is a secondary energy source; if released into the atmosphere, it will have a certain impact on environmental pollution and waste energy. To reduce environmental pollution and improve energy utilization, this embodiment dries and filters the discharged large amount of compressed air before sending it to the inlet of booster compressor 23 for pressurization, saving operating costs of air compressor 29 and reducing energy consumption, thus realizing the secondary utilization of compressed air. In addition, a buffer is provided inside the back pressure cylinder 16. Its function is to reduce the impact, vibration and wear of polymetallic nodules and seawater on the back pressure cylinder 16, which plays a buffering role and reduces the crushing and pulverization of polymetallic nodule particles, which is conducive to the settling of slurry in the storage tank 8 on the mining vessel 30.

Claims

1. A pneumatic lifting system with a back pressure device, comprising a lifting pipe (1) and an air compressor (29), wherein the compressed air outlet of the air compressor (29) is connected to the lifting pipe (1) via a main air supply pipe (26), characterized in that, The outlet of the riser (1) is connected to a back pressure cylinder (16), and when the riser (1) discharges a solid-gas-liquid three-phase fluid into the back pressure cylinder (16), the back pressure cylinder (16) is maintained at a first pressure, which is a positive pressure. The back pressure cylinder (16) is provided with a gas outlet, and a first valve (19) is provided at the gas outlet to adjust the magnitude of the first pressure in the back pressure cylinder (16) to control the flow rate of the solid-gas-liquid three-phase fluid in the riser (1).

2. The pneumatic lifting system according to claim 1, characterized in that, One end of the first valve (19) is connected to the gas outlet, and the other end of the first valve (19) is connected to the inlet of a booster (23) through the first gas pipeline (22). The outlet of the booster (23) is connected to the main gas pipeline (26) through the second gas pipeline (24). A one-way valve (25) is provided on the second gas pipeline (24).

3. The pneumatic lifting system according to claim 2, characterized in that, One end of the first valve (19) is connected to the gas outlet through a three-way pipe (18), and the other end of the three-way pipe (18) is provided with a second valve (17) for connecting the back pressure cylinder (16) with the outside.

4. The pneumatic lifting system according to claim 2, characterized in that, The first gas pipeline (22) is equipped with a cleaning device for cleaning gas, which includes a refrigerated dryer (20) and a filter (21) in sequence according to the gas flow direction.

5. The pneumatic lifting system according to claim 1, characterized in that, The back pressure cylinder (16) is provided with a buffer for buffering the solid-gas-liquid three-phase fluid force discharged from the outlet of the riser pipe (1).

6. The pneumatic lifting system according to claim 5, characterized in that, The outlet of the lifting pipe (1) is located in the middle of the back pressure cylinder (16), and the buffer and the outlet of the lifting pipe (1) are arranged opposite to each other. The buffer includes a metal disc (14), wear-resistant rubber (15), a buffer spring (11), a connecting rod (12) and a guide cylinder (13). The wear-resistant rubber (15) is provided on the surface of the metal disc (14) and faces the outlet of the lifting pipe (1). The guide cylinder (13) is located on the outer wall of the back pressure cylinder (16). One end of the metal disc (14) and the connecting rod (12) are connected. The other end of the connecting rod (12) is movably located in the guide cylinder (13). The buffer spring (11) is sleeved on the connecting rod (12) and is locked between the metal disc (14) and the inner wall of the back pressure cylinder (16).

7. The pneumatic lifting system according to claim 1, characterized in that, The bottom outlet of the back pressure cylinder (16) is connected to a storage tank (8) through a connecting pipe (10). The diameter of the connecting pipe (10) is 1.5-2 times the diameter of the riser pipe (1). A seawater discharge pipe (3) is connected to the connecting pipe (10) through a third valve (9).

8. The pneumatic lifting system according to claim 7, characterized in that, The top overflow outlet of the storage tank (8) is connected to a secondary sedimentation tank (7), the top of the secondary sedimentation tank (7) is provided with an overflow water pipe (4), the storage tank (8) is connected to a seawater delivery pipe (6), the inlet end of the seawater delivery pipe (6) is located below the sea surface, and the end is provided with a submersible pump (5).

9. The pneumatic lifting system according to claim 7, characterized in that, When the riser pipe (1) discharges solid-gas-liquid three-phase fluid into the back pressure cylinder (16), the back pressure cylinder (16) is equipped with a liquid seal, and the liquid level in the back pressure cylinder (16) and the liquid level in the storage tank (8) are kept the same.

10. A method for pneumatic lifting of seabed ore using the pneumatic lifting system according to any one of claims 1-9, characterized in that, Includes the following steps: S1: Connect the back pressure cylinder (16) to the outside world and add seawater into the back pressure cylinder (16); S2: Close the connection between the back pressure cylinder (16) and the outside world, start the air compressor (29), and the compressed air compressed by the air compressor (29) is delivered to the riser pipe (1) through the air supply main pipe (26). Due to the injection of compressed air, the seabed ore is sucked from the bottom of the riser pipe (1) and lifted to the outlet of the riser pipe (1), and discharged into the back pressure cylinder (16) as a solid-gas-liquid three-phase fluid. During the lifting process, the back pressure cylinder (16) maintains positive pressure, and the flow rate of the solid-gas-liquid three-phase fluid in the riser pipe (1) is adjusted by the opening and closing degree of the first valve (19). S3: After the seabed ore is lifted, the air compressor (29) is turned off, and the back pressure cylinder (16) is connected to the outside world to release the internal pressure.

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