A degassing membrane decompression low-temperature distillation device for seawater desalination

Abstract

The application relates to a degassing membrane decompression low-temperature distillation device for seawater desalination, relates to the technical field of seawater desalination, and comprises a hot seawater tank, a hot water pump, a hydrophobic hollow fiber membrane assembly, a condenser, an ejector, a fresh water tank, a filter core filter, a cold water pump and a waste gas water heater. The application establishes a vacuum through the ejector, greatly reduces the boiling point of seawater, enables the whole distillation process to be efficiently carried out at low temperature, can utilize low-grade heat sources such as solar energy and industrial waste heat, greatly reduces the high heating energy consumption of the traditional distillation method, has an almost absolute interception rate for salt, ions, bacteria and viruses through the membrane distillation principle, and guarantees the purity of the output fresh water; the inherent cooling water of the system is used to drive the ejector to replace the external vacuum pump, independent vacuum equipment and energy consumption are saved, the manufacturing cost and operation cost of the device are obviously reduced, and the system structure is simplified.

Description

Technical Field

[0001] This application relates to the field of seawater desalination technology, and in particular to a degassing membrane vacuum distillation apparatus for seawater desalination. Background Technology

[0002] Seawater desalination has become an important source of new energy sources; the current mainstream seawater desalination technologies mainly include multi-stage flash distillation, multi-effect distillation, reverse osmosis, and electrodialysis. Distillation methods (such as multi-stage flash distillation and multi-effect distillation) require heating seawater to high temperatures (usually exceeding 100°C), which can lead to problems such as high energy consumption, severe equipment corrosion, and high risk of scaling. Reverse osmosis: relies on a high-pressure pump to provide pressure to overcome osmotic pressure (usually 5-8 MPa), which places high demands on the pump and membrane materials, consumes a lot of energy, and has strict requirements for feed water pretreatment.

[0003] Regarding the aforementioned technologies, these methods generally suffer from high equipment investment and high energy consumption, which limits their application in small- to medium-sized, distributed, or energy-constrained scenarios (such as islands, coastal rural areas, and ships).

[0004] Membrane distillation is an emerging thermally driven membrane process that utilizes the vapor pressure difference across a hydrophobic microporous membrane as the driving force for mass transfer. Theoretically, it can use low-temperature heat sources (such as industrial waste heat or solar energy) and promises to obtain high-purity permeate with relatively low energy consumption. However, traditional membrane distillation systems typically require an external vacuum pump or carrier gas to maintain the vapor pressure difference downstream of the membrane, which increases the system's complexity and energy consumption.

[0005] Therefore, there is an urgent need for a seawater desalination device that is simple in structure, low in energy consumption, requires no external vacuum pump, and is particularly suitable for small and medium-sized scales. Utility Model Content

[0006] The purpose of this application is to provide a degassing membrane vacuum distillation apparatus for seawater desalination.

[0007] In a first aspect, the degassing membrane vacuum low-temperature distillation apparatus for seawater desalination provided in this application adopts the following technical solution: it includes a hot seawater tank, a hot water pump, a hydrophobic hollow fiber membrane module, a condenser, an ejector, a freshwater tank, a filter cartridge, a cold water pump, and a waste gas water heater; the outlet of the seawater in the hot seawater tank is connected to the right end tube inlet of the hydrophobic hollow fiber membrane module through the hot water pump, and the hot seawater circulates inside the hydrophobic hollow fiber membrane module to form a hot water circuit; the cold seawater is connected to the left end tube inlet of the condenser through the outlet of the cold water pump, and an ejector is provided at the outlet of the cold water pump; the suction end of the ejector is connected to the upper left shell side of the condenser and the lower left shell side of the hydrophobic hollow fiber membrane module through an exhaust pipe; the lower left end of the condenser is provided with a freshwater outlet, which is connected to the freshwater tank through the freshwater tank.

[0008] By adopting the above technical solution, a complete and efficient seawater desalination system was constructed. Its core lies in using an ejector, with the essential cooling water flow in the system as the power source, to form and maintain a stable vacuum environment on the shell side of the condenser and hydrophobic hollow fiber membrane module.

[0009] Preferably, the right end shell side of the condenser is provided with a seawater outlet.

[0010] By adopting the above technical solution, an exhaust channel is provided for the uncondensed residual steam and potentially accumulated non-condensable gases in the shell side of the condenser, which works in conjunction with the suction action of the ejector.

[0011] Preferably, the upper right shell side of the hydrophobic hollow fiber membrane module is connected to the lower right shell side of the condenser, and the right shell side of the hydrophobic hollow fiber membrane module is connected to the condenser.

[0012] By adopting the above technical solution, a smooth steam flow path was established between the steam side of the membrane module and the shell side of the condenser.

[0013] Preferably, a filter cartridge is installed on the connecting pipeline between the hot water pump and the hydrophobic hollow fiber membrane module.

[0014] By adopting the above technical solutions, it is possible to effectively remove suspended particles, colloids and other possible pollutants from hot seawater, and prevent the hollow fiber membrane pores from being blocked or the membrane surface from being contaminated.

[0015] Preferably, the exhaust gas outlet at the left end of the hydrophobic hollow fiber membrane module is connected to an exhaust gas water heater, which is used to heat the seawater in the hot seawater tank.

[0016] By adopting the above technical solution, the cascade utilization and recovery of energy is realized. The exhaust gas (which usually still has a certain temperature) discharged from the hydrophobic hollow fiber membrane module transfers the residual heat to the original seawater entering the hot seawater tank in the exhaust gas water heater, thus preheating the seawater.

[0017] Preferably, the hydrophobic hollow fiber membrane assembly has a hollow fiber membrane inside, and the membrane material of the hollow fiber membrane is polypropylene, polyvinylidene fluoride or polytetrafluoroethylene, and the pore size of the hollow fiber membrane is 0.01μm~0.5μm.

[0018] By adopting the above technical solution, the key parameters of the core separation element were clarified. Polypropylene (PP), polyvinylidene fluoride (PVDF), or polytetrafluoroethylene (PTFE) are all strongly hydrophobic materials, which can effectively prevent liquid water from penetrating and only allow water vapor to pass through. The pore size range of 0.01μm to 0.5μm ensures a sufficiently high vapor flux.

[0019] Preferably, the condenser includes a shell, end caps, a condenser tube fixing plate, baffles, and condenser tubes. End caps are provided on the upper and lower sides of the shell, and the upper end cap is provided with a fresh water outlet. The lower end of the end caps and the condenser tube fixing plate are bolted to the condenser tube fixing plate. Two sets of baffles are provided inside the shell. One set of baffles is fixed to the upper right end of the shell, and the other set of baffles is fixed to the lower left end of the shell.

[0020] By adopting the above technical solution, a robust and efficient condensing unit is provided. The design of the baffle plate can change the flow path of the steam in the shell side, causing it to repeatedly laterally scour the condensing tube bundle.

[0021] Preferably, the inner side of the condenser tube fixing plate is provided with a condenser tube hole one, and the inner side of the baffle plate is provided with a condenser tube hole two. The structure of the condenser tube hole one matches the structure of the condenser tube hole two, and the condenser tube passes through the interior of the condenser tube hole one and the condenser tube hole two for fixation.

[0022] By adopting the above technical solution, it is ensured that all condenser tubes are accurately positioned and supported, maintaining the neat arrangement and stability of the tube bundle and preventing damage due to fluid-induced vibration during operation.

[0023] Preferably, the condenser tubes are provided in multiple groups, and each group of condenser tubes is spaced 22mm apart vertically and horizontally, and is distributed in an isosceles trapezoidal shape.

[0024] By adopting the above technical solution, the arrangement of the condenser tubes was optimized.

[0025] In summary, this application includes at least one of the following beneficial technical effects of a degassing membrane vacuum low-temperature distillation apparatus for seawater desalination: 1. By creating a vacuum through the ejector, the boiling point of seawater is significantly reduced, allowing the entire distillation process to be carried out efficiently at low temperatures. This not only utilizes low-grade heat sources such as solar energy and industrial waste heat, but also greatly reduces the high heating energy consumption of traditional distillation methods. 2. Through the principle of membrane distillation, only water vapor can pass through the hydrophobic membrane, which has a near-absolute rejection rate for salt, ions, bacteria, viruses, etc., ensuring the purity of the produced fresh water. 3. By using the system's inherent cooling water to drive the ejector instead of an external vacuum pump, the independent vacuum equipment and its energy consumption are eliminated, significantly reducing the manufacturing and operating costs of the device and simplifying the system structure. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the overall structure of Embodiment 1 of this application; Figure 2 This is a schematic diagram of the internal structure of the hydrophobic hollow fiber membrane module of Embodiment 1 of this application; Figure 3 This is a schematic diagram of the internal structure of the condenser in Embodiment 2 of this application; Figure 4 This is a schematic diagram of the end cap planar structure of Embodiment 2 of this application; Figure 5 This is a schematic diagram of the planar structure of the condenser tube fixing plate in Embodiment 2 of this application; Figure 6 This is a schematic diagram of the baffle plate planar structure of Embodiment 2 of this application; Figure 7 This is a schematic diagram of the planar structure of the condenser tube in Embodiment 2 of this application.

[0027] Explanation of reference numerals in the attached drawings: 1. Hot seawater tank; 2. Hot water pump; 3. Hydrophobic hollow fiber membrane module; 4. Condenser; 5. Ejector; 6. Fresh water tank; 7. Filter cartridge; 8. Cold water pump; 9. Waste gas water heater; 41. Shell; 42. End cap; 43. Condenser tube fixing plate; 44. Baffle plate; 45. Condenser tube; 431. Condenser tube hole one; 441. Condenser tube hole two. Detailed Implementation

[0028] The following is in conjunction with the appendix Figure 1 - Appendix Figure 7 This application will be described in further detail below.

[0029] Example 1: A degassing membrane vacuum low-temperature distillation apparatus for seawater desalination, referring to... Figure 1The system includes a hot seawater tank 1, a hot water pump 2, a hydrophobic hollow fiber membrane module 3, a condenser 4, an ejector 5, a freshwater tank 6, a filter cartridge 7, a cold water pump 8, and a waste gas water heater 9. The outlet of the seawater in the hot seawater tank 1 is connected to the right end tube inlet of the hydrophobic hollow fiber membrane module 3 via the hot water pump 2, and the hot seawater circulates inside the hydrophobic hollow fiber membrane module 3 to form a hot water loop. The cold seawater is connected to the left end tube inlet of the condenser 4 via the outlet of the cold water pump 8, and an ejector 5 is installed at the outlet of the cold water pump 8. The suction end of the ejector 5 is connected to the upper left shell side of the condenser 4 and the lower left shell side of the hydrophobic hollow fiber membrane module 3 via an exhaust pipe. The lower left end of the condenser 4 has a freshwater outlet, which is connected to the freshwater tank 6 via the freshwater tank, thus constructing a complete and efficient seawater desalination system. The core of this system lies in utilizing ejector 5, powered by the essential cooling water flow, to create and maintain a stable vacuum environment on the shell side of condenser 4 and hydrophobic hollow fiber membrane module 3. This allows hot seawater to evaporate at a temperature far below its atmospheric boiling point as it flows through the inner side of membrane module 3. Driven by the pressure difference, the water vapor permeates through the micropores of the hollow fiber membrane into the shell side and is then pumped to condenser 4 to condense into fresh water. This ingenious solution eliminates the need for an external vacuum pump required by traditional membrane distillation, achieving a dual reduction in equipment cost and operating energy consumption.

[0030] In some embodiments, a seawater outlet is provided on the right-hand shell side of the condenser 4, providing a discharge channel for uncondensed residual steam and potentially accumulated non-condensable gases in the shell side of the condenser 4. Combined with the suction action of the ejector 5, this ensures the long-term stability of the internal vacuum of the system, avoiding the problem of decreased heat and mass transfer efficiency due to the accumulation of non-condensable gases. The upper right shell side of the hydrophobic hollow fiber membrane module 3 is connected to the lower right shell side of the condenser 4, establishing a smooth steam flow path between the steam side of the membrane module and the shell side of the condenser 4. This design ensures that the water vapor generated in the hydrophobic hollow fiber membrane module 3 can be efficiently and with minimal resistance transported to the condenser 4 for condensation, optimizing steam transmission efficiency and thus improving the overall water production rate of the device.

[0031] In this application, a filter cartridge 7 is installed on the connecting pipeline between the hot water pump 2 and the hydrophobic hollow fiber membrane module 3. This filter effectively removes suspended particles, colloids, and other potential pollutants from the hot seawater, preventing blockage of the hollow fiber membrane pores or contamination of the membrane surface. This ensures the long-term stable operation of the membrane module, extends its service life, and maintains a stable water production flux. The exhaust gas outlet at the left end of the hydrophobic hollow fiber membrane module 3 is connected to an exhaust gas water heater 9, which heats the seawater in the hot seawater tank 1, achieving cascaded energy utilization and recovery. The exhaust gas discharged from the hydrophobic hollow fiber membrane module 3 (usually still at a certain temperature) transfers residual heat to the original seawater entering the hot seawater tank 1 in the exhaust gas water heater 9, preheating the seawater. This process reduces the additional energy required to heat the seawater to the target temperature, further improving the energy utilization efficiency of the entire system and reducing operating costs.

[0032] It should be noted that the hydrophobic hollow fiber membrane module 3 contains a hollow fiber membrane 31. The membrane material of the hollow fiber membrane 31 is polypropylene, polyvinylidene fluoride (PVDF), or polytetrafluoroethylene (PTFE), and the pore size of the hollow fiber membrane 31 is 0.01 μm to 0.5 μm, thus defining the key parameters of the core separation element. Polypropylene (PP), polyvinylidene fluoride (PVDF), or polytetrafluoroethylene (PTFE) are all strongly hydrophobic materials, effectively preventing liquid water permeation and allowing only water vapor to pass through. The pore size range of 0.01 μm to 0.5 μm ensures a sufficiently high steam flux while completely blocking the passage of salt ions, macromolecules, and microorganisms, thereby ensuring the high purity of the produced water.

[0033] The implementation principle of this application embodiment is as follows: During operation, the preheated seawater is heated to a suitable low temperature in the hot seawater tank 1, driven by the hot water pump 2, flows through the filter cartridge 7 to remove impurities, and then enters the tube side of the hydrophobic hollow fiber membrane module 3 for circulation. At the same time, the cold seawater is pressurized by the cold water pump 8 and divided into two paths: one path enters the tube side of the condenser 4 as a cooling medium; Another high-pressure water flow enters ejector 5. Ejector 5 uses the Venturi effect to generate and maintain the vacuum required by the system at its suction end. This negative pressure environment acts on the shell side of the hydrophobic hollow fiber membrane module 3 and the shell side of the condenser 4 through the pipeline. Inside the hydrophobic hollow fiber membrane module 3, the saturated vapor pressure of the hot seawater in the tube side is much higher than the vacuum environment in the shell side, driving water molecules to evaporate rapidly; the generated water vapor enters the shell side through the micropores of the hollow fiber membrane 31 and is pumped to the condenser 4 under the action of pressure difference. In condenser 4, water vapor exchanges heat with the cold seawater flowing inside the pipe, condenses into liquid fresh water, and is collected by gravity and flows into fresh water tank 6 from the bottom fresh water outlet to complete the collection; trace amounts of non-condensable gases that may exist in the shell side of the membrane module are continuously extracted by ejector 5 to ensure the system vacuum is stable; the concentrated waste gas discharged from the membrane module 3, which still has residual heat, preheats the raw seawater entering the hot seawater tank 1 in the waste gas water heater 9 to achieve energy recovery.

[0034] Example 2: A degassing membrane vacuum low-temperature distillation device for seawater desalination, the condenser 4 includes a shell 41, end caps 42, condenser tube fixing plate 43, baffles 44, and condenser tubes 45. End caps 42 are arranged opposite each other on the upper and lower sides of the shell 41. The upper end cap 42 is provided with a fresh water outlet. The lower end of the end caps 42 and the condenser tube fixing plate 43 is bolted to the condenser tube fixing plate 43. Two sets of baffles 44 are arranged inside the shell 41. One set of baffles 44 is fixed to the upper right end of the shell 41, and the other set of baffles 44 is fixed to the lower left end of the shell 41, providing a stable and efficient condensation unit. The design of the baffle plate 44 alters the flow path of steam in the shell side, causing it to repeatedly laterally scour the bundle of condenser tubes 45. This increases the contact time and turbulence between the steam and the cold tube wall, disrupting the thermal boundary layer and significantly enhancing the condensation heat transfer process, thereby improving condensation efficiency. The inner side of the condenser tube fixing plate 43 has a first condenser tube hole 431, and the inner side of the baffle plate 44 has a second condenser tube hole 441. The structure of the first condenser tube hole 431 matches the structure of the second condenser tube hole 441. The condenser tubes 45 are fixed inside the first condenser tube hole 431 and the second condenser tube hole 441, ensuring that all condenser tubes 45 are precisely positioned and supported, maintaining the neat arrangement and stability of the tube bundle, preventing damage due to fluid-induced vibration during operation, and ensuring the sealing between the tube side and the shell side. Multiple sets of condenser tubes 45 are provided, with each set spaced 22mm apart vertically and horizontally, and distributed in an isosceles trapezoidal shape, thus optimizing the arrangement of the condenser tubes 45. The isosceles trapezoidal distribution and uniform 22mm spacing allow for the arrangement of the maximum heat exchange area within a limited shell space. At the same time, it creates a uniform and smooth channel for the flow of shell-side steam and the dripping of condensate, avoiding local dead zones or flow short circuits, maximizing the use of heat exchange space and improving overall condensation performance.

[0035] Based on Example 1, this embodiment optimizes the structure of the core component, condenser 4. Its working principle is the same as that of Example 1, and its performance improvement is mainly due to the internal structural design of condenser 4. When water vapor flows in the condenser shell 41, it is guided by two sets of staggered baffles 44, which force it to change its flow direction multiple times and repeatedly laterally wash the bundle of condenser tubes 45 arranged in a tight isosceles trapezoidal shape (22mm spacing). This design greatly enhances the turbulence on the steam side, destroys the thermal boundary layer of the tube wall, and allows water vapor to have more complete and efficient heat exchange with the low-temperature condenser tube 45 wall, thereby rapidly condensing into liquid water.

[0036] The embodiments described in this specific implementation are preferred embodiments of this application and are not intended to limit the scope of protection of this application. Identical components are represented by the same reference numerals. Therefore, all equivalent changes made to the structure, shape, and principle of this application should be covered within the scope of protection of this application.

Claims

1. A degassing membrane vacuum distillation apparatus for seawater desalination, characterized in that, The system includes a hot seawater tank (1), a hot water pump (2), a hydrophobic hollow fiber membrane module (3), a condenser (4), an ejector (5), a freshwater tank (6), a filter cartridge (7), a cold water pump (8), and a waste gas water heater (9). The outlet of the seawater in the hot seawater tank (1) is connected to the right end tube inlet of the hydrophobic hollow fiber membrane module (3) through the hot water pump (2). The hot seawater circulates inside the hydrophobic hollow fiber membrane module (3) to form a hot water circuit. The cold seawater is connected to the left end tube inlet of the condenser (4) through the outlet of the cold water pump (8). An ejector (5) is provided at the outlet of the cold water pump (8). The suction end of the ejector (5) is connected to the upper left shell side of the condenser (4) and the lower left shell side of the hydrophobic hollow fiber membrane module (3) through an air extraction pipe. The lower left end of the condenser (4) is provided with a freshwater outlet, which is connected to the freshwater tank (6) through the freshwater tank.

2. The degassing membrane vacuum distillation apparatus for seawater desalination according to claim 1, characterized in that, The condenser (4) has a seawater outlet on the right shell side.

3. The degassing membrane vacuum distillation apparatus for seawater desalination according to claim 1, characterized in that, The upper right shell side of the hydrophobic hollow fiber membrane module (3) is connected to the lower right shell side of the condenser (4), and the right shell side of the hydrophobic hollow fiber membrane module (3) is connected to the condenser (4).

4. The degassing membrane vacuum distillation apparatus for seawater desalination according to claim 1, characterized in that, A filter cartridge (7) is installed on the connecting pipe between the hot water pump (2) and the hydrophobic hollow fiber membrane module (3).

5. A degassing membrane vacuum distillation apparatus for seawater desalination according to claim 1, characterized in that, The exhaust gas outlet at the left end of the hydrophobic hollow fiber membrane module (3) is connected to the exhaust gas water heater (9), which is used to heat the seawater in the hot seawater tank (1).

6. A degassing membrane vacuum distillation apparatus for seawater desalination according to claim 1, characterized in that, The hydrophobic hollow fiber membrane module (3) is provided with a hollow fiber membrane (31) inside. The membrane material of the hollow fiber membrane (31) is polypropylene, polyvinylidene fluoride or polytetrafluoroethylene, and the pore size of the hollow fiber membrane (31) is 0.01μm~0.5μm.

7. A degassing membrane vacuum distillation apparatus for seawater desalination according to claim 1, characterized in that, The condenser (4) includes a shell (41), an end cap (42), a condenser tube fixing plate (43), a baffle plate (44), and a condenser tube (45). The upper and lower sides of the shell (41) are provided with end caps (42). The end cap (42) at the upper end is provided with a fresh water outlet. The lower end of the end cap (42) and the condenser tube fixing plate (43) are bolted together. The shell (41) is provided with two sets of baffle plates (44). One set of baffle plates (44) is fixed to the upper right end of the shell (41), and the other set of baffle plates (44) is fixed to the lower left end of the shell (41).

8. A degassing membrane vacuum distillation apparatus for seawater desalination according to claim 7, characterized in that, The inner side of the condenser fixing plate (43) is provided with a condenser hole one (431), and the inner side of the baffle plate (44) is provided with a condenser hole two (441). The structure of the condenser hole one (431) matches the structure of the condenser hole two (441). The condenser (45) passes through the interior of the condenser hole one (431) and the condenser hole two (441) for fixation.

9. A degassing membrane vacuum distillation apparatus for seawater desalination according to claim 7, characterized in that, The condenser tubes (45) are arranged in multiple groups, and each group of condenser tubes (45) is spaced 22mm apart in all directions and is arranged in an isosceles trapezoidal shape.

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