Multi-stage seawater desalination device and method based on carbon dioxide hydrate method

Abstract

The invention provides a multistage seawater desalination device and method based on a carbon dioxide hydrate method, and belongs to the technical field of hydrate application, and the multistage seawater desalination device comprises three parts of gas-water conveying, multistage hydrate generation and decomposition control and product storage and discharge. The multi-stage hydrate generation and decomposition control part is composed of multiple stages, each stage comprises a reactor, a gas booster pump, a drying agent tank, a constant-temperature water bath, a pressure and temperature sensor and a data acquisition system, the reactors are used for hydrate generation and decomposition, and the gas-water conveying part comprises a gas source, a seawater clarification tank, the gas booster pump, the drying agent tank and a water suction pump. The product storage and discharge part is composed of multiple stages and comprises a salt discharge tank, a decomposition water tank, a fresh water tank, a water suction pump and a three-way pipe fitting, the seawater desalination efficiency and the energy utilization rate are improved through a more efficient and convenient scheme, cyclic utilization and recycling of carbon dioxide are achieved, and the concentration of carbon dioxide in the atmosphere is reduced, so that the ecological cleaning effect is achieved; and finally, large-scale seawater desalination is realized.

Description

Technical Field

[0001] The present invention relates to the technical field of hydrate application, and in particular to a multi-stage seawater desalination device and method based on a carbon dioxide hydrate method. Background Art

[0002] In recent years, the global freshwater resources are in short supply. Many countries have actively engaged in the research and development and application exploration of seawater desalination technology. China has also achieved remarkable technological achievements in the field of seawater desalination. At present, a variety of seawater desalination technologies using the hydrate method have emerged, including ball milling, deep sea low temperature and high pressure environment method, propane and other gas hydrate methods, etc., but the equipment of these methods is relatively complex and has high requirements, and there is still a lot of room for optimization of energy consumption. The basic principle of seawater desalination by carbon dioxide hydrate method is that when water molecules in seawater combine with carbon dioxide hydration agent to form hydrates, under the action of salt removal effect, sodium, magnesium, chlorine and other ions in seawater cannot enter the lattice and remain in the solution, and then separate and decompose the hydrate to obtain fresh water. At present, in the published patent literature and research results, the output and efficiency of seawater desalination technology by hydrate method are still limited by the formation conditions of hydrates, separation technology, energy consumption and other aspects. Summary of the invention

[0003] The purpose of the present invention is to provide a multi-stage seawater desalination device and method based on the carbon dioxide hydrate method, which aims to improve the seawater desalination efficiency and energy utilization rate through a more efficient and convenient solution, realize the recycling and resource utilization of carbon dioxide, reduce the carbon dioxide concentration in the atmosphere to achieve the effect of cleaning the ecology, and ultimately realize large-scale seawater desalination.

[0004] To achieve the above object, the present invention provides the following technical solutions:

[0005] In a first aspect, a multi-stage seawater desalination device based on a carbon dioxide hydrate method includes a gas-water transport section, a multi-stage hydrate generation and decomposition control section, and a product storage and discharge section.

[0006] The multi-stage hydrate generation and decomposition control part is composed of multiple stages, each stage includes a reactor, a gas booster pump, a desiccant tank, a constant temperature water bath, a pressure sensor, a temperature sensor and a data acquisition system. The reactor is used to generate and decompose hydrates. Each reactor is arranged inside a constant temperature water bath. Each stage of the reactor is connected to a corresponding pressure sensor and a temperature sensor. Each pressure sensor and temperature sensor is connected to an A / D conversion module through a data line, and the A / D conversion module is connected to the data acquisition system through a data line. A No. 1 passage connecting the gas booster pump and the desiccant tank is arranged on one side of the top of each stage of the reactor. The top of the reactor of the upper stage is connected to the top of the reactor of the lower stage through the No. 1 passage.

[0007] The gas-water transportation part includes a gas source, a seawater clarification tank, a gas booster pump, a desiccant tank and a water pump. One end of the gas source is connected to the top of the first-stage reactor through the gas booster pump and the desiccant tank to form a gas transportation passage. The seawater clarification tank is connected to the top of the first-stage reactor through the water pump to form a water transportation passage. The other end of the gas source is connected to the top of the final-stage reactor through the final-stage No. 1 passage to form a gas recovery passage.

[0008] The product storage and discharge part is composed of multiple stages, including a salt discharge tank, a decomposition water tank, a fresh water tank, a water pump and a three-way pipe fitting. The bottom outlet of each stage of the reactor is connected to the salt discharge tank, the bottom outlet of the final reactor is connected to the fresh water tank, and the bottom outlets of the remaining reactors are connected to the decomposition water tank. The decomposition water tank is connected to the top of the next stage reactor through a No. 2 passage provided with a water pump, and the three-way pipe fitting is connected to the top of the final reactor through a branch of the No. 1 passage of the final stage.

[0009] Furthermore, each stage of the reactor includes a hydraulic lifting agitator, a filter element and a mechanical knob. The hydraulic lifting agitator is fixedly arranged on the top of the reactor, the filter element is arranged at the bottom of the reactor, and the mechanical knob is arranged on the outside of the bottom of the reactor. The mechanical knob adopts a spiral structure and is used to adjust the pore size of the filter element.

[0010] Furthermore, the hydraulic lifting agitator includes a base, a hydraulic lifting support, a hull support, a bearing seat, a skeleton oil seal, a stirring shaft, a stirring blade, a reducer and a motor. The base is arranged at the bottom of the hydraulic lifting agitator, and a hydraulic lifting support is arranged on the base. A hull support is arranged on the top of the hydraulic lifting support. A reducer and a bearing seat are arranged at both ends of the hull support, respectively. The upper transmission of the reducer is connected with a motor. A skeleton oil seal is arranged at the bottom of the bearing seat. The bearing seat is fixed to the top of each stage of the reactor through the skeleton oil seal. The bearing seat and the skeleton oil seal are vacuum sealed. The stirring shaft is arranged in the bearing seat. The stirring shaft passes downward through the skeleton oil seal and the top of each stage of the reactor and then extends into the interior of each stage of the reactor. The stirring shaft is provided with a stirring blade, and the output end of the reducer is connected to the top of the stirring shaft by means of a pulley or a sprocket mechanism.

[0011] Furthermore, a sealing ring is arranged inside the top of each stage of the reactor.

[0012] Furthermore, the bottom of the first-stage reactor adopts a sharp configuration, and the bottoms of the remaining reactors adopt a smooth configuration.

[0013] Furthermore, a valve is provided between the gas booster pump and the reactor in each No. 1 passage, a PID valve is provided between the desiccant tank and the next-stage reactor in each No. 1 passage, a valve is provided between the desiccant tank and the gas source in the last-stage No. 1 passage, and a valve is provided between the branch of the last-stage No. 1 passage and the three-way pipe fitting.

[0014] A valve is provided between the gas source and the gas booster pump in the gas transmission passage, a PID valve is provided between the desiccant tank and the first-stage reactor in the gas transmission passage, and valves are provided between the seawater clarification tank and the water pump and between the water pump and the first-stage reactor in the water transmission passage.

[0015] A valve is provided between the bottom outlet of each stage of the reactor and the salt discharge tank, a valve is provided between the bottom outlet of the final stage of the reactor and the fresh water tank, valves are provided between the bottom outlets of the remaining reactors and the decomposition water tanks, a valve is provided between each decomposition water tank and the corresponding water pump on the No. 2 passage, and a valve is provided between each water pump on the No. 2 passage and the reactor of the next stage.

[0016] Furthermore, the desiccant tank and the three-way pipe fitting are both made of corrosion-resistant stainless steel, each stage of the reactor and the hydraulic lifting agitator are both made of corrosion-resistant stainless steel 316L, the hydraulic lifting agitator is used to accelerate the hydrate formation process, and the pressure resistance value of each stage of the reactor and the hydraulic lifting agitator is ≥30MPa; the temperature of the constant temperature water bath is controlled between -10 and 20°C.

[0017] Furthermore, the interior of the desiccant tank is paved with silica gel and activated alumina in alternating layers, and the thickness of each layer is precisely controlled in the range of 10 to 30 cm.

[0018] Furthermore, the filter element is made of polytetrafluoroethylene.

[0019] In the second aspect, a method for desalinating seawater using the device comprises the following steps:

[0020] S1. Gas-water transportation: The carbon dioxide gas in the gas source is pressurized to about twice the equilibrium pressure of carbon dioxide hydrate by the gas booster pump of the gas-water transportation part, and then enters the desiccant tank of the gas-water transportation part for drying. At the same time, seawater is introduced into the seawater clarification tank to treat impurities. The treated seawater is pumped in by the pump of the gas-water transportation part and merged into the first-stage reactor together with the dried carbon dioxide gas pipeline.

[0021] S2. Multi-stage hydrate generation and decomposition control: First, open the constant temperature water bath and set the temperature to no higher than 3°C, start the first-stage hydrate generation process, stir at high speed in the first-stage reactor, and the filter element at the lower end is in a tightly closed state with the minimum pores. After the hydrate is generated, open the valve of the salt discharge tank in sequence, rotate the mechanical knob counterclockwise to expand the pores of the filter element, discharge the lower layer of salt in the first-stage reactor to the salt discharge tank, and then rotate the mechanical knob clockwise to reset the pores. Then reduce the pressure to decompose the hydrate, open the valve of the decomposition water tank in turn, rotate clockwise to enlarge the pores, discharge the decomposed water, and open the upper valve of the first-stage reactor at the same time, and transport the decomposed carbon dioxide and decomposed water to the next-stage reactor as raw materials.

[0022] The next-stage reactor repeats the steps of hydrate formation, salt removal, hydrate decomposition, etc. until the final fresh water is stored in the fresh water tank of the final reactor. The pressure and temperature of each reactor are monitored by pressure sensors and temperature sensors respectively, and connected to the data acquisition system for analysis and storage.

[0023] S3. Product storage and discharge: The salt produced by the hydrate formation process in the first-stage reactor and other reactors except the final stage enters the salt discharge tank, and the decomposed water produced by the hydrate decomposition process enters the decomposition water tank. The operation is carried out in sequence until the salt produced by the hydrate formation process in the final reactor enters the salt discharge tank, and the fresh water produced by the hydrate decomposition process enters the fresh water tank. The carbon dioxide decomposed by the final reactor is recycled through the gas booster pump and the desiccant tank. The branch of the final No. 1 passage is equipped with a three-way pipe fitting, which has the functions of emptying and replenishing the gas source.

[0024] Advantages of the present invention:

[0025] 1. Use desiccant tanks to dry carbon dioxide, avoiding the formation of hydrates that may clog the valves while ensuring smooth system operation.

[0026] 2. The multi-stage hydrate formation and decomposition control part adopts an external mechanical knob reactor, and a polytetrafluoroethylene filter element is arranged at the lower end. The mechanical knob is a spiral structure that can flexibly adjust the pores of the filter element composed of polytetrafluoroethylene to accurately separate salt, decomposed water and fresh water.

[0027] 3. The bottom of the reactor is unique. The bottom of the first-stage reactor adopts a sharp configuration to promote salt drainage, and the bottoms of the other reactors adopt a smooth configuration, which can realize the high-pressure and low-temperature generation and pressure-reducing decomposition of hydrates in the same reactor, effectively reducing losses.

[0028] 4. During the hydrate formation process, high-speed stirring is used to accelerate the reaction, constant pressure air intake ensures high yield, and the agitator has a lifting function, which is designed to adapt to the desalination operation needs of different water volumes and improve desalination efficiency.

[0029] 5. The decomposed water and the carbon dioxide produced by the decomposition are used as the next-level raw materials to achieve multiple desalination of seawater and recycling of carbon dioxide. Reactors can be added as needed until fresh water that meets the requirements is obtained, meeting the needs of large-scale freshwater production and carbon resource utilization; the setting of the three-way pipe fitting can be used to exhaust carbon dioxide and replenish fresh carbon dioxide gas source; the system has a compact structure, integrated functions, stable and reliable operation, intermittent cycle operation to optimize costs, energy saving and environmental protection, and meets high standards of industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a structural schematic diagram of the device of the present invention;

[0031] Figure 2 This is a schematic diagram of the structure of the reactor and the hydraulic lifting agitator in the present invention;

[0032] Figure 3 It is a schematic diagram of the enlarged structure of the lower end of the reactor in the present invention;

[0033] In the figure: 1. Reactor, 1-1. First-stage reactor, 1-2. Final-stage reactor, 2. Hydraulic lifting agitator, 2-1. Base, 2-2. Hydraulic lifting bracket, 2-3. Hull bracket, 2-4. Bearing seat, 2-5. Skeleton oil seal, 2-6. Stirring shaft, 2-7. Stirring blade, 2-8. Reducer, 2-9. Motor, 3. Sealing ring, 4. Filter element, 5. Mechanical knob, 6. Gas booster pump, 7. Desiccant tank, 8. Constant temperature water bath, 9. Pressure sensor, 10. Temperature sensor, 11. Data acquisition system, 12. Gas source, 13. Seawater clarification tank, 14. Water pump, 15. Salt discharge tank, 16. Decomposition tank, 17. Fresh water tank, 18. Three-way pipe fitting, 19. Valve, 20. PID valve. DETAILED DESCRIPTION

[0034] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention. Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention.

[0035] like Figure 1 and Figure 2 As shown, a multi-stage seawater desalination device based on the carbon dioxide hydrate method includes a gas-water transmission part, a multi-stage hydrate generation and decomposition control part and a product storage and discharge part.

[0036] The multi-stage hydrate generation and decomposition control part is composed of multiple stages. In this embodiment, the multiple stages are two stages. Each stage includes a reactor 1, a gas booster pump 6, a desiccant tank 7, a constant temperature water bath 8, a pressure sensor 9, a temperature sensor 10 and a data acquisition system 11. The reactor 1 is used to generate and decompose hydrates. Each reactor 1 is arranged inside the constant temperature water bath 8. Each stage of the reactor 1 is connected to a corresponding pressure sensor 9 and a temperature sensor 10. Each pressure sensor 9 and temperature sensor 10 are respectively connected to an A / D conversion module through a data line, and the A / D conversion module is connected to the data acquisition system 11 through a data line. A No. 1 passage connecting the gas booster pump 6 and the desiccant tank 7 is provided on one side of the top of each stage of the reactor 1. The top of the reactor of the upper stage is connected to the top of the reactor of the lower stage through the No. 1 passage.

[0037] The gas-water transport part includes a gas source 12, a seawater clarification tank 13, a gas booster pump 6, a desiccant tank 7 and a water pump 14. One end of the gas source 12 is connected to the top of the first-stage reactor 1-1 through the gas booster pump 6 and the desiccant tank 7 to form a gas transport passage. The seawater clarification tank 13 is connected to the top of the first-stage reactor 1-1 through the water pump 14 to form a water transport passage. The other end of the gas source 12 is connected to the top of the final-stage reactor 1-2 through the final-stage No. 1 passage to form a gas recovery passage.

[0038] The product storage and discharge part is composed of multiple stages, including a salt removal tank 15, a decomposition water tank 16, a fresh water tank 17, a pump 14 and a three-way pipe fitting 18. The bottom outlet of each stage of the reactor 1 is connected to the salt removal tank 15, the bottom outlet of the final reactor 1-2 is connected to the fresh water tank 17, and the bottom outlets of the remaining reactors are connected to the decomposition water tank 16. The decomposition water tank 16 is connected to the top of the next stage reactor through a No. 2 passage provided with a pump. In this embodiment, the decomposition water tank 16 connected to the bottom outlet of the first-stage reactor 1-1 is connected to the top of the final reactor 1-2 through a No. 2 passage provided with a pump 14.

[0039] The three-way pipe fitting 18 is connected to the top of the final reactor 1-2 through the branch of the final first passage. The three-way pipe fitting 18 can be used to exhaust carbon dioxide and replenish fresh carbon dioxide gas source to ensure stable and flexible operation of the system.

[0040] The decomposed water stored in the decomposed water tank 16 and the carbon dioxide generated by the decompression decomposition in the first-stage reactor are respectively input into the final-stage reactor 1-2, and the desalinated seawater is finally stored in the fresh water tank 17. This process not only realizes secondary seawater desalination, but also promotes the recycling of carbon dioxide.

[0041] The salt removal tank 15 can be replaced in time according to the actual working conditions to ensure the continuous and efficient operation of the system. The carbon dioxide produced after the decomposition of the final reactor 1-2 can be recycled and connected to the initial gas source 12 through the gas booster pump 6 and the desiccant tank 7 as the raw material for the next stage reaction. During the process, the gas source 12 can be connected to the gas booster pump 6 to replenish gas in time to make up for the loss of carbon dioxide.

[0042] As a preferred embodiment of the present invention, each stage of the reactor 1 includes a hydraulic lifting agitator 2, a filter element 4 and a mechanical knob 5. The hydraulic lifting agitator 2 is fixedly arranged on the top of the reactor 1. The hydraulic lifting agitator 2 has a lifting function, which can realize the high-pressure and low-temperature generation and pressure reduction decomposition of hydrates in the same reactor.

[0043] like Figure 1 and Figure 3 As shown, the filter element 4 is arranged at the bottom of the reactor 1, and the mechanical knob 5 is arranged outside the bottom of the reactor 1. The mechanical knob 5 adopts a spiral structure, and generates a linear displacement when rotating to drive the extrusion component to adjust the pore size of the filter element 4. When the mechanical knob 5 rotates clockwise, the extrusion component approaches the filter element 4, and radial pressure is applied to reduce its pore size; when it rotates counterclockwise, the extrusion component moves away, the filter element 4 recovers by elasticity, and the pore size becomes larger.

[0044] As a preferred embodiment of the present invention, Figure 2 As shown, the hydraulic lifting agitator 2 includes a base 2-1, a hydraulic lifting support 2-2, a hull support 2-3, a bearing seat 2-4, a skeleton oil seal 2-5, a stirring shaft 2-6, a stirring blade 2-7, a reducer 2-8 and a motor 2-9. The base 2-1 is arranged at the bottom of the hydraulic lifting agitator 2, and the hydraulic lifting support 2-2 is arranged on the base 2-1. The top of the hydraulic lifting support 2-2 is arranged with a hull support 2-3, and the two ends of the hull support 2-3 are respectively provided with a reducer 2-8 and a bearing seat 2-4, and the upper transmission of the reducer 2-8 is connected to the motor 2-9, and the bottom end of the bearing seat 2-4 is provided with a skeleton oil seal 2-5, and the bearing seat 2-4 is fixed to the top of each stage of the reactor 1 through the skeleton oil seal 2-5. The bearing seat 2-4 and the skeleton oil seal 2-5 are vacuum sealed to ensure the sealing inside the device when the stirring shaft is raised and lowered, thereby ensuring the stirring effect. The stirring shaft 2-6 is arranged in the bearing seat 2-4, and the stirring shaft 2-6 passes downward through the skeleton oil seal 2-5 and the top of each stage of the reactor 1 and then extends into the interior of each stage of the reactor 1. The stirring shaft 2-6 is provided with a stirring blade 2-7, and the output end of the reducer 2-8 is connected to the top of the stirring shaft 2-6 by means of a pulley or a sprocket mechanism, so as to achieve lifting and lowering while completing the stirring of the material inside the reactor 1. When the hydraulic lifting bracket 2-2 is in operation, it can drive the stirring shaft 2-6, the stirring blade 2-7, the reducer 2-8 and the motor 2-9 to rise and fall synchronously in the reactor 1.

[0045] like Figure 1 and Figure 2 As shown, as a preferred embodiment of the present invention, a sealing ring 3 is provided in the top of each stage of the reactor 1, which can not only enhance the sealing but also facilitate replacement, thereby ensuring the efficient operation of the hydraulic lifting agitator 2.

[0046] In view of the fact that the amount of salt discharged decreases step by step during the desalination process, the reactor design is differentiated. As a preferred embodiment of the present invention, the bottom of the first-stage reactor 1-1 adopts a sharp configuration to promote the outflow of salt. The bottoms of the remaining reactors adopt a smooth configuration. In this embodiment, the bottom of the final-stage reactor 1-2 adopts a smooth configuration.

[0047] As a preferred embodiment of the present invention, a valve 19 is provided between the gas booster pump 6 and the reactor 1 in each No. 1 passage, a PID valve 20 is provided between the desiccant tank 7 and the next-stage reactor in each No. 1 passage, a valve 19 is provided between the desiccant tank 7 and the gas source 12 in the last-stage No. 1 passage, and a valve 19 is provided between the branch of the last-stage No. 1 passage and the three-way pipe fitting 18.

[0048] A valve 19 is provided between the gas source 12 and the gas booster pump 6 in the gas delivery passage, a PID valve 20 is provided between the desiccant tank 7 and the first-stage reactor 1-1 in the gas delivery passage, and valves 19 are provided between the seawater clarification tank 13 and the water pump 14 and between the water pump 14 and the first-stage reactor 1-1 in the water delivery passage.

[0049] A valve 19 is provided between the bottom outlet of each stage reactor 1 and the salt discharge tank 15, a valve 19 is provided between the bottom outlet of the final stage reactor 1-2 and the fresh water tank 17, a valve 19 is provided between the bottom outlets of the remaining reactors and the decomposition water tank 16, a valve 19 is provided between each decomposition water tank 16 and the corresponding water pump 14 on the No. 2 passage, and a valve 19 is provided between each water pump 14 on the No. 2 passage and the next stage reactor.

[0050] In this embodiment, a valve 19 is provided between the bottom outlet of the first-stage reactor 1 - 1 and the decomposition water tank 16 .

[0051] As a preferred embodiment of the present invention, the desiccant tank 7 and the three-way pipe fitting 18 are both made of corrosion-resistant stainless steel, each stage of the reactor 1 and the hydraulic lifting agitator 2 are both made of corrosion-resistant stainless steel 316L, the hydraulic lifting agitator 2 is used to accelerate the hydrate formation process, and the pressure resistance value of each stage of the reactor 1 and the hydraulic lifting agitator 2 is ≥30MPa; the temperature of the constant temperature water bath 8 is controlled between -10 and 20°C, biased towards low temperature to ensure hydrate formation.

[0052] As a preferred embodiment of the present invention, the interior of the desiccant tank 7 is paved with silica gel and activated alumina in alternating layers, and the thickness of each layer is precisely controlled in the range of 10 to 30 cm.

[0053] As a preferred embodiment of the present invention, the filter element 4 is made of polytetrafluoroethylene.

[0054] The method for desalinating seawater using the device comprises the following steps:

[0055] S1. Gas-water transportation: The carbon dioxide gas in the gas source 12 is pressurized to about twice the equilibrium pressure of the carbon dioxide hydrate phase by the gas booster pump 6 of the gas-water transportation part, and then enters the desiccant tank 7 of the gas-water transportation part for drying. At the same time, seawater is introduced into the seawater clarification tank 13 to treat impurities. The treated seawater is pumped in by the pumping pump 14 of the gas-water transportation part and merged into the first-stage reactor 1-1 together with the dried carbon dioxide gas branch pipeline.

[0056] S2. Multi-stage hydrate generation and decomposition control: First, open the constant temperature water bath 8 and set the temperature to no higher than 3°C, start the first-stage hydrate generation process, stir at high speed in the first-stage reactor 1-1, and the lower end filter element 4 is in a tight closed state with the minimum pores. After the hydrate is generated, open the valve of the salt discharge tank 15 in sequence, rotate the mechanical knob 5 counterclockwise to expand the pores of the filter element 4, discharge the lower layer of salt in the first-stage reactor 1-1 to the salt discharge tank 15, and then rotate the mechanical knob 5 clockwise to reset the pores. Then reduce the pressure to decompose the hydrate, open the valve 19 of the decomposition water tank 16 in turn, rotate the large pores clockwise to discharge the decomposed water, and open the upper end valve 19 of the first-stage reactor 1-1 at the same time, and transport the decomposed carbon dioxide and decomposed water to the next-stage reactor as raw materials, respectively. In this embodiment, they are directly transported to the final reactor 1-2.

[0057] The final reactor 1-2 repeats the steps of hydrate formation, salt removal, hydrate decomposition, etc. until the final fresh water is stored in the fresh water tank 17 of the final reactor 1-2. The pressure and temperature of each reactor 1 are monitored by a pressure sensor 9 and a temperature sensor 10 respectively, and are connected to a data acquisition system 11 for analysis and storage.

[0058] S3. Product storage and discharge: The salt produced by the hydrate formation process in the first-stage reactor 1-1 and other reactors except the final stage enters the salt discharge tank 15, and the decomposed water produced by the hydrate decomposition process enters the decomposition water tank 16, and the operation is carried out in sequence until the salt produced by the hydrate formation process in the final stage reactor 1-2 enters the salt discharge tank 15, and the fresh water produced by the hydrate decomposition process enters the fresh water tank 17. In this embodiment, there are two stages of reactors, namely the first-stage reactor 1-1 and the final reactor 1-2.

[0059] The carbon dioxide decomposed by the final reactor 1-2 is recycled through the gas booster pump 6 and the desiccant tank 7. The branch of the final No. 1 passage is provided with a three-way pipe fitting 18, which has the functions of emptying and replenishing the gas source.

[0060] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art can still adjust the technical solutions described in the above embodiments or replace some of the technical features by equivalents. Therefore, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalent technologies, the present invention is also intended to include these modifications and variations.

Claims

1. A multi-stage seawater desalination device based on the carbon dioxide hydrate method, comprising a gas-water transport section, a multi-stage hydrate generation and decomposition control section, and a product storage and discharge section, characterized in that: The multi-stage hydrate generation and decomposition control part is composed of multiple stages, each stage includes a reactor, a gas booster pump, a desiccant tank, a constant temperature water bath, a pressure sensor, a temperature sensor and a data acquisition system. The reactor is used to generate and decompose hydrates. Each reactor is arranged inside the constant temperature water bath. Each stage of the reactor is connected to a corresponding pressure sensor and a temperature sensor. Each pressure sensor and temperature sensor is connected to an A / D conversion module through a data line, and the A / D conversion module is connected to the data acquisition system through a data line. A No. 1 passage connecting the gas booster pump and the desiccant tank is arranged on one side of the top of each stage of the reactor. The top of the reactor of the upper stage is connected to the top of the reactor of the lower stage through the No. 1 passage. The gas-water transport part includes a gas source, a seawater clarification tank, a gas booster pump, a desiccant tank and a water pump. One end of the gas source is connected to the top of the first-stage reactor through the gas booster pump and the desiccant tank to form a gas transport passage. The seawater clarification tank is connected to the top of the first-stage reactor through the water pump to form a water transport passage. The other end of the gas source is connected to the top of the final-stage reactor through the final-stage No. 1 passage to form a gas recovery passage. The product storage and discharge part is composed of multiple stages, including a salt discharge tank, a decomposition water tank, a fresh water tank, a water pump and a three-way pipe fitting. The bottom outlet of each stage of the reactor is connected to the salt discharge tank, the bottom outlet of the final reactor is connected to the fresh water tank, and the bottom outlets of the remaining reactors are connected to the decomposition water tank. The decomposition water tank is connected to the top of the next stage reactor through a No. 2 passage provided with a water pump, and the three-way pipe fitting is connected to the top of the final reactor through a branch of the No. 1 passage of the final stage.

2. The multi-stage seawater desalination device based on the carbon dioxide hydrate method according to claim 1, characterized in that: Each stage of the reactor includes a hydraulic lifting agitator, a filter element and a mechanical knob. The hydraulic lifting agitator is fixedly arranged on the top of the reactor, the filter element is arranged at the bottom of the reactor, and the mechanical knob is arranged on the outside of the bottom of the reactor. The mechanical knob adopts a spiral structure and is used to adjust the pore size of the filter element.

3. The multi-stage seawater desalination device based on the carbon dioxide hydrate method according to claim 2, characterized in that: The hydraulic lifting agitator comprises a base, a hydraulic lifting bracket, a hull bracket, a bearing seat, a skeleton oil seal, a stirring shaft, a stirring blade, a reducer and a motor. The base is arranged at the bottom of the hydraulic lifting agitator, and a hydraulic lifting bracket is arranged on the base. A hull bracket is arranged on the top of the hydraulic lifting bracket. A reducer and a bearing seat are arranged at both ends of the hull bracket, respectively. The upper transmission of the reducer is connected with a motor. A skeleton oil seal is arranged at the bottom end of the bearing seat. The bearing seat is fixed to the top of each stage of the reactor through the skeleton oil seal. The bearing seat and the skeleton oil seal are vacuum sealed. The stirring shaft is arranged in the bearing seat. The stirring shaft passes downward through the skeleton oil seal and the top of each stage of the reactor and then extends into the interior of each stage of the reactor. A stirring blade is arranged on the stirring shaft. The output end of the reducer is connected to the top of the stirring shaft by means of a pulley or a sprocket mechanism.

4. The multi-stage seawater desalination device based on the carbon dioxide hydrate method according to claim 3, characterized in that: A sealing ring is arranged at the top of each reactor stage.

5. The multi-stage seawater desalination device based on the carbon dioxide hydrate method according to claim 4, characterized in that: The bottom of the first-stage reactor adopts a sharp configuration, and the bottoms of the remaining reactors adopt a smooth configuration.

6. The multi-stage seawater desalination device based on the carbon dioxide hydrate method according to claim 5, characterized in that: A valve is provided between the gas booster pump and the reactor in each No. 1 passage, a PID valve is provided between the desiccant tank and the next-stage reactor in each No. 1 passage, a valve is provided between the desiccant tank and the gas source in the last No. 1 passage, and a valve is provided between the branch of the last No. 1 passage and the three-way pipe fitting; A valve is provided between the gas source and the gas booster pump in the gas delivery passage, a PID valve is provided between the desiccant tank and the first-stage reactor in the gas delivery passage, and valves are provided between the seawater clarification tank and the water pump, and between the water pump and the first-stage reactor in the water delivery passage; A valve is provided between the bottom outlet of each stage of the reactor and the salt discharge tank, a valve is provided between the bottom outlet of the final stage of the reactor and the fresh water tank, valves are provided between the bottom outlets of the remaining reactors and the decomposition water tanks, a valve is provided between each decomposition water tank and the corresponding water pump on the No. 2 passage, and a valve is provided between each water pump on the No. 2 passage and the reactor of the next stage.

7. The multi-stage seawater desalination device based on the carbon dioxide hydrate method according to claim 6, characterized in that: The desiccant tank and the three-way pipe fitting are both made of corrosion-resistant stainless steel, each stage of the reactor and the hydraulic lifting agitator are both made of corrosion-resistant stainless steel 316L, the hydraulic lifting agitator is used to accelerate the hydrate formation process, and the pressure resistance value of each stage of the reactor and the hydraulic lifting agitator is ≥30MPa; the temperature of the constant temperature water bath is controlled between -10 and 20°C.

8. The multi-stage seawater desalination device based on the carbon dioxide hydrate method according to claim 7, characterized in that: The interior of the desiccant tank is paved with silica gel and activated alumina in alternating layers, and the thickness of each layer is precisely controlled in the range of 10 to 30 cm.

9. The multi-stage seawater desalination device based on the carbon dioxide hydrate method according to claim 8, characterized in that: The filter element is made of polytetrafluoroethylene.

10. A method for desalinating seawater using the device according to any one of claims 1 to 9, characterized in that: Here are the steps: S1. Gas-water transportation: The carbon dioxide gas in the gas source is pressurized to about twice the equilibrium pressure of carbon dioxide hydrate by the gas booster pump of the gas-water transportation part, and then enters the desiccant tank of the gas-water transportation part for drying. At the same time, seawater is introduced into the seawater clarification tank to treat impurities. The treated seawater is pumped in by the pump of the gas-water transportation part and merged into the primary reactor together with the dried carbon dioxide gas branch pipeline; S2. Multi-stage hydrate formation and decomposition control: First, turn on the constant temperature water bath and set the temperature to no higher than 3°C, start the first-stage hydrate formation process, stir at high speed in the first-stage reactor, and the filter element at the lower end is in a tightly closed state with the minimum pores. After the hydrate is generated, open the salt discharge tank valve in sequence, rotate the mechanical knob counterclockwise to expand the pores of the filter element, discharge the lower layer of salt in the first-stage reactor to the salt discharge tank, and then rotate the mechanical knob clockwise to reset the pores. Then reduce the pressure to decompose the hydrate, open the decomposition water tank valve in turn, rotate clockwise to enlarge the pores, discharge the decomposed water, and at the same time open the upper valve of the first-stage reactor, and transport the decomposed carbon dioxide and decomposed water to the next-stage reactor as raw materials; The next reactor repeats the steps of hydrate formation, salt removal, hydrate decomposition, etc. until the final fresh water is stored in the fresh water tank of the final reactor. The pressure and temperature of each reactor are monitored by pressure sensors and temperature sensors respectively, and connected to the data acquisition system for analysis and storage; S3. Product storage and discharge: The salt produced by the hydrate formation process in the first-stage reactor and other reactors except the final stage enters the salt discharge tank, and the decomposed water produced by the hydrate decomposition process enters the decomposition water tank. The operation is carried out in sequence until the salt produced by the hydrate formation process in the final reactor enters the salt discharge tank, and the fresh water produced by the hydrate decomposition process enters the fresh water tank. The carbon dioxide decomposed by the final reactor is recycled through the gas booster pump and the desiccant tank. The branch of the final No. 1 passage is equipped with a three-way pipe fitting, which has the functions of emptying and replenishing the gas source.

Images