Sea water desalination closed circulation device and system

Abstract

The invention relates to the technical field of seawater desalination, and discloses a seawater desalination closed circulation device and system.The seawater circulation unit stores seawater containing inorganic salt and can heat the seawater to the preset temperature of membrane distillation; the membrane distillation unit is used for desalting the heated seawater conveyed by the seawater circulation unit and generating desalted water vapor, and a condensation assembly of the purge gas circulation unit is used for performing multi-stage cooling on the desalted water vapor and producing and recycling condensed water; the purging assembly is used for collecting dry and cold gas discharged from the condensation assembly and pumping the dry and cold gas into the membrane distillation unit for cyclic utilization; the thermal circulation unit is located between the seawater circulation unit and the condensation assembly, and the thermal circulation unit is used for conveying the circulation working medium of the condensation assembly to the seawater circulation unit for thermal circulation utilization and conducting cooling circulation utilization on the circulation working medium subjected to thermal circulation utilization. Compared with the prior art, the energy consumption can be saved by about 20%, and the seawater desalination cost is reduced by about 25%.

Description

Technical Field

[0001] The present application belongs to the technical field of seawater desalination, and specifically relates to a seawater desalination closed-loop device and system. Background Art

[0002] With the rapid growth of the global population and the continuous development of industry, the shortage of fresh water resources has become a global problem that needs to be solved urgently. Seawater desalination is an effective way to solve the fresh water crisis.

[0003] The current cost of desalination ranges from 5 to 8 yuan per ton, but this is still relatively high compared to the price of tap water. Desalination costs are composed of multiple factors, primarily equipment and material investment, energy consumption, pipeline network construction, and pretreatment. Energy consumption accounts for over 60% of the cost. For desalination projects with a capacity of 10,000 tons or more, if the heat consumed by distillation is converted into electricity, the resulting figure is considerable. Desalination currently primarily utilizes reverse osmosis (RO), but RO membranes are expensive and easily contaminated during use, typically requiring replacement every three to five years.

[0004] Among various desalination technologies, membrane distillation utilizes the vapor pressure difference across the membrane as the driving force for mass transfer, using heat to propel water vapor through the porous, hydrophobic membrane material for desalination. This technology offers significant advantages in treating highly concentrated, highly contaminated saltwater and utilizing low-grade heat such as industrial waste heat, as well as solar and geothermal energy. However, existing membrane desalination technologies face challenges with high costs and energy consumption, which require urgent solutions. Summary of the Invention

[0005] The purpose of this application is to provide a closed-loop desalination device and system for reducing the energy consumption cost of seawater desalination.

[0006] In order to achieve the above objectives, the present application provides, on one hand, a seawater desalination closed-loop device, comprising: A seawater circulation unit, storing seawater containing inorganic salts and capable of heating the seawater to a preset membrane distillation temperature; a membrane distillation unit for desalinating the heated seawater delivered by the seawater circulation unit and generating desalinated water vapor; a purge gas circulation unit, wherein the purge gas circulation unit and the seawater circulation unit are respectively located on both sides of the membrane distillation unit, the purge gas circulation unit comprising a condensation assembly and a purge assembly, the condensation assembly being used to perform multi-stage cooling on the desalted water vapor and produce condensed water for recycling, and the purge assembly being used to collect the dry cold gas discharged from the condensation assembly and pump it to the membrane distillation unit for recycling; The heat circulation unit is located between the seawater circulation unit and the condensation component. The heat circulation unit is used to transport the circulating working fluid of the condensation component to the seawater circulation unit for heat circulation utilization, and to cool and circulate the circulating working fluid after heat circulation utilization.

[0007] In some embodiments, the seawater circulation unit includes a liquid storage tank, a medium-temperature heater and a high-temperature supplementary heat device connected in sequence by pipelines. A booster pump is also provided on the pipeline between the liquid storage tank and the medium-temperature heater. The booster pump is used to increase the pressure of the seawater in the pipeline. The liquid storage tank stores seawater containing inorganic salts. The medium-temperature heater is used to heat the seawater discharged from the liquid storage tank to a first preset temperature. The high-temperature supplementary heat device is arranged in the membrane distillation unit and is used to heat the seawater with a first preset temperature to a membrane distillation preset temperature, wherein the membrane distillation preset temperature is greater than the first preset temperature.

[0008] In some embodiments, the seawater circulation unit further includes a make-up water circuit and a sewage circuit respectively arranged at the side end and the bottom end of the liquid storage tank, the make-up water circuit is provided with a first heat exchanger, and a second heat exchanger is provided on the pipeline connecting the make-up water circuit and the sewage circuit. The low-concentration and low-temperature seawater is heated by the first heat exchanger and the second heat exchanger respectively and then replenished into the liquid storage tank along the make-up water circuit. The sewage circuit is used to receive the high-concentration seawater discharged from the liquid storage tank and discharge it to the salt field after cooling it by the second heat exchanger.

[0009] In some embodiments, the membrane distillation unit includes a distillation body and a distillation membrane, the distillation membrane is used to divide the distillation body into a first cavity and a second cavity, the high-temperature heat replenisher is arranged in the first cavity, and the second cavity is provided with a heating humidifier, the distillation membrane is used to perform membrane distillation on the seawater heated by the high-temperature heat replenisher and form desalted water vapor, the heating humidifier is used to absorb the high-temperature desalted water vapor from the imported dry cold air to heat and humidify it into a humid hot gas and transport it to the condensation component.

[0010] In some embodiments, the condensation component includes a medium-temperature condenser and a low-temperature condenser connected by a pipe, the inlet end of the medium-temperature condenser is connected to the outlet end of the second cavity, the outlet end of the medium-temperature condenser discharges condensed water through a first condensed water discharge pipe, the medium-temperature air discharged from the medium-temperature condenser enters the low-temperature condenser for low-temperature condensation, and the outlet end of the low-temperature condenser discharges condensed water through a second condensed water discharge pipe. A circulation pipe is also connected between the medium-temperature condenser and the low-temperature condenser, and the dry cold gas discharged from the low-temperature condenser can enter the medium-temperature condenser for recycling.

[0011] In some embodiments, the purge assembly includes a purge pipeline and a fan provided on the purge pipeline, the purge pipeline is connected between the medium-temperature condenser and the second cavity, the fan is used to pass a portion of the dry cold gas discharged from the medium-temperature condenser into the second cavity through the purge pipeline for recycling, and the other portion of the dry cold gas discharged from the medium-temperature condenser enters the low-temperature condenser through the pipeline.

[0012] In some embodiments, a recovery tank is further provided on the purge pipeline between the blower and the distillation body. The recovery tank is connected to the first condensed water discharge pipeline, and the recovery tank is used to recover the condensed water formed in the purge pipeline.

[0013] In some embodiments, the thermal cycling unit comprises: A compressor, wherein the inlet end of the compressor is connected to the circulation outlet of the low-temperature condenser, and the superheated working medium discharged from the outlet end of the compressor passes through the high-temperature supplementary heater and the medium-temperature heater in sequence through a first heat circulation pipeline for pre-cooling; The supercooling component is used to supercool the circulating working fluid after pre-cooling; The throttle valve assembly throttles the circulating working medium after the supercooling treatment and returns it to the circulation inlet of the low-temperature condenser.

[0014] In some embodiments, the subcooling component includes: The first heat exchanger cools the circulating working fluid flowing out of the medium-temperature heater after cooling by replenishing water with seawater; a secondary subcooler for collecting condensed water discharged from the first condensed water discharge pipeline and the second condensed water discharge pipeline, and performing secondary cooling on the circulating working medium after the primary cooling by using the condensed water; The three-stage subcooler cools the circulating working fluid for the third time after the secondary cooling.

[0015] In some embodiments, the seawater desalination closed-loop device further includes a recovery tank connected to the outlet end of the secondary supercooler and used to collect condensed water discharged from the secondary supercooler after supercooling.

[0016] In some embodiments, the three-stage subcooler includes an inlet end, an outlet end, a first circulation end and a second circulation end. The inlet end is connected to the secondary subcooler, the outlet end is connected to the low-temperature condenser, and a first electromagnetic throttle valve is provided on the connecting pipeline between the two. The first circulation end is connected to the compressor, and a second electromagnetic throttle valve is provided on the connecting pipeline between the second circulation end and the outlet end. The first electromagnetic throttle valve is used to significantly reduce the pressure and temperature of the circulating working fluid to achieve heat absorption in the evaporator, and the second electromagnetic throttle valve is used to slightly throttle and cool the circulating working fluid that has been cooled three times to achieve the function of replenishing air and increasing enthalpy.

[0017] In some embodiments, the circulating working fluid is a non-azeotropic mixed working fluid, and supercritical carbon dioxide working fluid may also be used, and the temperature glide phenomenon during the cooling process of the circulating working fluid is used to reduce the irreversibility of heat exchange.

[0018] In addition, a second aspect of the present application provides a seawater desalination closed circulation system, comprising an electronic control device and the seawater desalination closed circulation device as described above.

[0019] Through the above technical solution, the seawater to be desalinated stored in the seawater circulation unit is heated and then enters the membrane distillation unit for membrane distillation to obtain desalinated water vapor; the desalinated water vapor enters the condensation component of the purge gas circulation unit for condensation to form condensed water for recycling, and the purge component pumps the dry cold gas discharged from the condensation component into the membrane distillation unit for recycling, thereby absorbing the invalid heat load in the condensation component and improving the seawater desalination efficiency of membrane distillation. In addition, the present application sets a thermal circulation unit, which is used to transport the circulating working fluid of the condensation component to the seawater circulation unit for thermal recycling, and cools and recycles the circulating working fluid after thermal recycling, thereby reducing the energy consumption of the entire device and reducing the cost of seawater desalination.

[0020] Other features and advantages of the embodiments of the present application will be described in detail in the subsequent detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The accompanying drawings are used to provide a further understanding of the embodiments of the present application and constitute a part of the specification. Together with the following specific embodiments, they are used to explain the embodiments of the present application, but do not constitute a limitation on the embodiments of the present application. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without inventive work. In the drawings: Figure 1 This is a schematic diagram of the structure of the closed-loop seawater desalination device of this application.

[0022] Description of Reference Numerals 11. Liquid storage tank; 42. Recovery tank; 12. Medium-temperature heater; L1. Make-up water circuit; 13. High-temperature supplementary heat exchanger; L2. Sewage water circuit; 14. First heat exchanger; L3. First condensate discharge pipeline; 15. Second heat exchanger; L4. Second condensate discharge pipeline; 16. Booster pump; L5. Circulation pipeline; 21. Distillation body; L6. Purge pipeline; 22. Distillation membrane; 51. Compressor; 23. Heating humidifier; 52. Secondary subcooler; 31. Medium-temperature condenser; 53. Tertiary subcooler; 32. Low-temperature condenser; 54. First electromagnetic throttle valve; 41. Fan; 55. Second electromagnetic throttle valve. DETAILED DESCRIPTION

[0023] The following describes the specific embodiments of the present application in detail with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present application and are not intended to limit the present application.

[0024] The closed-cycle seawater desalination device according to the present application will be described below with reference to the accompanying drawings.

[0025] like Figure 1 As shown, the present application provides a closed-loop desalination device, including a seawater circulation unit, a membrane distillation unit, a purge gas circulation unit and a heat circulation unit; the seawater circulation unit stores seawater containing inorganic salts and can heat the seawater to a preset temperature for membrane distillation; the membrane distillation unit is used to desalinate and desalinate the heated seawater transported by the seawater circulation unit and produce desalinated water vapor, the purge gas circulation unit and the seawater circulation unit are respectively located on both sides of the membrane distillation unit, the purge gas circulation unit includes a condensation component and a purge component, the condensation component is used to perform multi-stage cooling on the desalted water vapor and produce condensed water for recycling, the purge component is used to collect dry cold gas discharged from the condensation component and pump it to the membrane distillation unit for recycling; the heat circulation unit is located between the seawater circulation unit and the condensation component, the heat circulation unit is used to transport the circulating working fluid of the condensation component to the seawater circulation unit for thermal recycling, and to cool and recycle the circulating working fluid that has undergone thermal recycling. Wherein, the seawater circulation unit is formed as shown in FIG. Figure 1 As shown in the purple circulation loop, the thermal cycle unit forms Figure 1 The green circulation loop shown in the figure is formed as follows: Figure 1 Red tubing shown.

[0026] In this embodiment, the seawater to be desalinated stored in the seawater circulation unit is heated and then enters the membrane distillation unit for membrane distillation to obtain desalinated water vapor; the desalinated water vapor enters the condensation component of the purge gas circulation unit for condensation to form condensed water for recycling, and the purge component pumps the dry cold gas discharged from the condensation component into the membrane distillation unit for recycling, thereby absorbing the ineffective heat load in the condensation component and improving the seawater desalination efficiency of membrane distillation. In addition, by providing a thermal circulation unit, the present application can recycle the energy of the circulating working fluid in the condensation component, thereby reducing the energy consumption of the entire device and lowering the cost of seawater desalination.

[0027] This device integrates and couples a seawater circulation unit, a membrane distillation unit, a purge gas circulation unit, and a thermal circulation unit, innovatively combining multiple technical advantages such as supplemental heat membrane distillation technology, positive pressure air sweeping and negative pressure condensation and purge technology, and three-stage non-azeotropic mixed working fluid subcooling. The thermal circulation unit efficiently recovers ineffective heat load, raising the seawater temperature and increasing the vaporization rate of water molecules on the surface of the distillation membrane 22. This heat drives the water vapor through the porous hydrophobic membrane material for desalination, achieving efficient and low-energy water production from seawater. This invention can be widely used in the field of seawater desalination. Compared with existing membrane desalination technologies, it can save energy consumption by approximately 20% and reduce desalination costs by approximately 25%, showing broad prospects for promotion and application.

[0028] In some embodiments, the seawater circulation unit includes a liquid storage tank 11, a medium-temperature heater 12, and a high-temperature supplementary heater 13, which are connected in sequence by pipes. The liquid storage tank 11 stores seawater containing inorganic salts. The medium-temperature heater 12 is used to heat the seawater discharged from the liquid storage tank 11 to a first preset temperature. The high-temperature supplementary heater 13 is arranged in the membrane distillation unit and is used to heat the seawater having the first preset temperature to a membrane distillation preset temperature, wherein the membrane distillation preset temperature is greater than the first preset temperature.

[0029] In this embodiment, to improve the operating efficiency of the membrane distillation unit, the heat exchanger used to heat seawater transported from the liquid storage tank 11 is divided into a high-temperature section and a medium-temperature section. The medium-temperature section comprises a medium-temperature heater 12, while the high-temperature section comprises a high-temperature supplemental heater 13 located within the membrane distillation unit. The medium-temperature heater 12 is located in the pipeline between the liquid storage tank 11 and the membrane distillation unit. The medium-temperature heater 12 heats the seawater to a first predetermined temperature. The high-temperature supplemental heater 13 then continuously supplements the seawater at the first predetermined temperature within the membrane distillation unit. This continuously replenishes the heat energy consumed by the vaporization of water molecules in the seawater on the membrane surface, maintaining a higher transport driving force on the membrane surface, ensuring uniform and efficient mass transfer across the entire surface of the distillation membrane 22, and improving the utilization rate of the distillation membrane 22.

[0030] Furthermore, a booster pump 16 is provided in the pipeline between the liquid storage tank 11 and the medium-temperature heater 12. This booster pump 16 is used to increase the pressure of the seawater in the pipeline. By providing the booster pump 16, one end of which is connected to the top of the liquid storage tank 11, and the pipeline extending below the liquid level in the liquid storage tank 11, the seawater transported from the liquid storage tank 11 is raised to a certain pressure by the booster pump 16 before entering the medium-temperature heater 12 for heating, ensuring smooth seawater transportation.

[0031] In order to make full use of the low-temperature cold source of seawater replenishment and the waste heat of sewage seawater, the seawater circulation unit also includes a replenishing water circuit L1 and a sewage circuit L2, which are respectively arranged at the side end and the bottom end of the liquid storage tank 11. A first heat exchanger 14 is provided on the replenishing water circuit L1, and a second heat exchanger 15 is provided on the pipeline connecting the replenishing water circuit L1 and the sewage circuit L2. The low-concentration and low-temperature seawater is heated by the first heat exchanger 14 and the second heat exchanger 15 respectively, and then replenished into the liquid storage tank 11 along the replenishing water circuit L1. The sewage circuit L2 is used to receive the high-concentration seawater discharged from the liquid storage tank 11 and is discharged to the salt field after cooling through the second heat exchanger 15.

[0032] The first heat exchanger 14 not only increases the temperature of the incoming low-concentration, low-temperature seawater, reducing energy consumption, but also lowers the temperature of the non-azeotropic refrigerant mixture after the condenser in the thermal cycle unit, thereby increasing the refrigerant's subcooling. The second heat exchanger 15 effectively recovers the waste heat of the discharged high-concentration seawater to heat the seawater in the make-up water loop L1. This allows the discharged high-concentration seawater to be cooled while the incoming low-temperature, low-concentration seawater is heated, thereby reducing system heat loss.

[0033] In some embodiments, the membrane distillation unit includes a distillation body 21 and a distillation membrane 22. The distillation membrane 22 is used to divide the distillation body 21 into a first cavity and a second cavity. The high-temperature heater 13 is arranged in the first cavity, and a heating humidifier 23 is provided in the second cavity. The distillation membrane 22 is used to perform membrane distillation on the seawater heated by the high-temperature heater 13 and form desalted water vapor. The heating humidifier is used to import dry cold air to absorb high-temperature desalted water vapor, heat and humidify it into humid hot gas, and transport it to the condensation component.

[0034] In this embodiment, when the device is in operation, water molecules in the high-temperature seawater on the high-temperature supplemental heater 13 are transferred through the distillation membrane 22 into the second chamber. This is driven by the water vapor pressure on the surface of the distillation membrane 22 being higher than the water vapor partial pressure in the second chamber. This pressure differential drives the water in the seawater to continuously migrate into the second chamber, achieving desalination. The heating humidifier 23 within the second chamber heats the desalinated water vapor within the second chamber, generating a hot and humid gas that is transported to the medium-temperature condenser 31 for condensation.

[0035] In some embodiments, the condensation component includes a medium-temperature condenser 31 and a low-temperature condenser 32 connected by pipes, the inlet end of the medium-temperature condenser 31 is connected to the outlet end of the second cavity, the outlet end of the medium-temperature condenser 31 discharges condensed water through a first condensed water discharge pipe, and the outlet end of the low-temperature condenser 32 discharges condensed water through a second condensed water discharge pipe. A circulation pipe L5 is also connected between the medium-temperature condenser 31 and the low-temperature condenser 32, and the dry cold gas discharged from the low-temperature condenser 32 can enter the medium-temperature condenser 31 for recycling.

[0036] In this embodiment, the hot and humid gas discharged from the outlet of the second cavity after membrane distillation can enter the medium-temperature condenser 31 through the inlet of the medium-temperature condenser 31 for condensation. A portion of the condensed water is formed, which is discharged and recovered through the first condensed water discharge pipeline, and the remaining portion is formed into dry cold gas. The dry cold gas enters the low-temperature condenser 32 for further low-temperature condensation. After condensation in the low-temperature condenser 32, condensed water is formed and discharged and recovered through the second condensed water discharge pipeline, while the remaining dry cold gas returns to the medium-temperature condenser 31 for recycling, thereby reducing energy loss. The circulating medium in the entire purge gas circulation unit can be air, nitrogen, etc.

[0037] In some embodiments, the purge assembly includes a purge line L6 and a fan 41 provided on the purge line L6, and the purge line L6 is connected between the medium-temperature condenser 31 and the second cavity. In order to improve the efficiency of the purge gas circulation unit in absorbing water vapor, positive pressure air sweeping and negative pressure condensation are adopted. Compared with the prior art in which the fan 41 is placed before the condenser, in this embodiment, by adjusting the position of the fan 41 from before the condenser to after the condenser, the fan 41 can receive the dry cold gas discharged from the condenser, so that the inlet working medium of the fan 41 is adjusted from high-temperature and high-humidity gas to dry cold gas. On the one hand, it can reduce the power consumption of the fan 41, improve the operating reliability of the fan 41, and further reduce the humidity of the dry cold gas. In addition, the negative pressure condensation scheme of the present application adopts a two-stage series condenser: a medium-temperature condenser and a low-temperature condenser. The medium-temperature condenser receives the hot and humid gas discharged from the membrane distillation unit and performs medium-temperature condensation. The fan 41 is used to transfer the dry and cold gas discharged from the medium-temperature condenser 31 through the purge pipe L6 into the second cavity for recycling to absorb water vapor on the surface of the distillation membrane 22; another part of the dry and cold gas discharged from the medium-temperature condenser enters the low-temperature condenser through the pipeline for further low-temperature condensation, so that the moisture in the high-temperature and high-humidity purge gas can be efficiently recovered, thereby improving the efficiency of seawater desalination.

[0038] When the dry cold gas is purged and recovered in the purge line L6, some of the water vapor in the dry cold gas precipitates as condensed water due to the increased pressure. Therefore, a recovery tank 42 is provided on the purge line L6 between the fan 41 and the distillation body 21. The recovery tank 42 is connected to the first condensed water discharge line and is used to recover the condensed water formed in the purge line L6, thereby improving the safe and reliable operation of the fan 41. Furthermore, to recover the condensed water in the purge line L6, the outlet of the recovery tank 42 is connected to the first condensed water discharge line, so that the condensed water in the purge line L6 can be collected in the first condensed water discharge line for discharge and recovery.

[0039] In some embodiments, the thermal circulation unit includes a compressor 51, a subcooling component and a throttle valve component; the inlet end of the compressor 51 is connected to the circulation outlet of the low-temperature condenser 32, and the superheated working fluid discharged from the outlet end of the compressor 51 passes through the first thermal circulation pipeline and sequentially passes through the high-temperature heater 13 and the medium-temperature heater 12 for pre-cooling; the subcooling component is used to subcool the circulating working fluid after pre-cooling; the throttle valve component throttles the circulating working fluid after subcooling and returns it to the circulation inlet of the low-temperature condenser 32.

[0040] In this embodiment, since the temperature of the circulating working fluid discharged from the outlet of the compressor 51 is very high, in order to make full use of this part of the heat energy, the outlet of the compressor 51 is connected to the high-temperature heater 13 and the medium-temperature heater 12 through the first heat circulation pipeline, so that the heat energy of the compressor 51 will be used by the high-temperature heater 13 and the medium-temperature heater 12 in turn, so that the temperature of the circulating working fluid after passing through the high-temperature heater 13 and the medium-temperature heater 12 gradually decreases, thereby achieving pre-cooling. The circulating working fluid after pre-cooling passes through the supercooling component for supercooling treatment, and finally passes through the throttling treatment of the throttle valve component to complete the entire thermal cycle process. Through the thermal cycle process of the thermal cycle unit, the thermal energy of the circulating working fluid can be supplied to the high-temperature heater 13 and the medium-temperature heater 12 for use, and cooled and cooled by the supplementary cold seawater of the first heat exchanger 14 and the recovered condensed water of the secondary supercooler 52, so that the energy inside the entire device can be fully utilized to reduce energy consumption and the cost of the entire seawater desalination.

[0041] In some embodiments, the subcooling assembly includes a first heat exchanger 14, a secondary subcooler 52, and a tertiary subcooler 53, connected by pipes along the direction of the circulating refrigerant. The first heat exchanger 14 uses seawater to provide primary cooling for the circulating refrigerant flowing out of the medium-temperature heater 12 after cooling. The secondary subcooler 52 collects condensed water discharged from the first and second condensed water discharge lines and uses the condensed water to provide secondary cooling for the circulating refrigerant after the primary cooling. The tertiary subcooler 53 provides tertiary cooling for the circulating refrigerant after the secondary cooling. The three-stage subcooling device can significantly increase the subcooling degree of the non-azeotropic refrigerant mixture and improve the enthalpy difference between the inlet and outlet of the evaporator.

[0042] Furthermore, the closed-loop desalination system also includes a recovery tank connected to the outlet of the secondary subcooler 52 and used to collect condensed water discharged from the secondary subcooler 52 after being supercooled. The condensed water collected from the coils of the medium-temperature condenser and the low-temperature condenser is then transported to the secondary subcooler 52 for secondary subcooling of the circulating working fluid, thereby increasing the cooling capacity of the heat pump system. The water is then sent to the recovery tank for pure water recovery, completing the fresh water collection process.

[0043] In some embodiments, the three-stage subcooler 53 includes an inlet end, an outlet end, a first circulation end and a second circulation end. The inlet end is connected to the secondary subcooler 52, and the outlet end is connected to the low-temperature condenser. A first electromagnetic throttle valve 54 is also provided on the connecting pipeline between the two. The first circulation end is connected to the compressor 51, and a second electromagnetic throttle valve 55 is provided on the connecting pipeline between the second circulation end and the outlet end. The first electromagnetic throttle valve 54 is used to significantly reduce the pressure and temperature of the circulating working fluid to achieve heat absorption in the evaporator. The second electromagnetic throttle valve 55 is used to slightly throttle and cool the circulating working fluid that has been cooled three times to achieve the function of replenishing air and increasing enthalpy.

[0044] The first electromagnetic throttle valve 54 and the second electromagnetic throttle valve are both common throttle valves in heat pump circulation systems in the prior art, capable of reducing the pressure and temperature of the circulating working fluid. During operation, after the high-pressure liquid circulating working fluid passes through the small holes or narrow channels of the electromagnetic throttle valves, its pressure drops sharply (approximately an isenthalpic process), and some of the liquid flashes to vapor, with the temperature subsequently decreasing. Furthermore, the circulating working fluid flow rate can be adjusted according to system requirements, ensuring full utilization of the evaporator and avoiding liquid hammer in compressor 51. Before the two electromagnetic throttle valves throttle, the circulating working fluid undergoes three stages of subcooling to ensure sufficient subcooling of the liquid circulating working fluid (typically ≥5°C) to avoid excessive flash gas causing a drop in flow rate.

[0045] In some embodiments, the circulating working fluid is a non-azeotropic mixture, such as R245fa / R152a, R134a / R245fa, etc. Supercritical carbon dioxide can also be used as a working fluid to reduce the irreversibility of heat exchange by utilizing the temperature glide phenomenon during the cooling process of the circulating working fluid.

[0046] In addition, this application also proposes a closed-loop desalination system, comprising an electronic control device and the closed-loop desalination device described above. The electronic control device may be a power supply device that provides power to the closed-loop desalination device to ensure normal operation of the closed-loop desalination device. Furthermore, because this system utilizes all embodiments of the closed-loop desalination device described above, it possesses all the beneficial effects of the closed-loop desalination device described above, which will not be described in detail here.

[0047] In the description of this application, it should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be understood to indicate or imply relative importance or implicitly specify the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include at least one of such features. In the description of this application, "plurality" means at least two, for example, two, three, etc., unless otherwise specifically defined.

[0048] In this application, unless otherwise specified or limited, the terms "installed," "connected," "connect," "fixed," etc. should be understood in a broad sense. For example, they can refer to fixed connection, detachable connection, or integration; mechanical connection, electrical connection, or communication; direct connection or indirect connection through an intermediate medium; internal communication between two elements or interaction between two elements, unless otherwise specified. Those skilled in the art will understand the specific meanings of the above terms in this application based on specific circumstances.

[0049] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification and features of different embodiments or examples without contradiction.

[0050] Although the embodiments of the present application have been shown and described above, it can be understood that the above embodiments are exemplary and cannot be understood as limitations on the present application. Ordinary technicians in this field can change, modify, replace and modify the above embodiments within the scope of the present application.

Claims

1. A closed-loop desalination device, characterized in that: include: A seawater circulation unit, storing seawater containing inorganic salts and capable of heating the seawater to a preset membrane distillation temperature; a membrane distillation unit for desalinating the heated seawater delivered by the seawater circulation unit and generating desalinated water vapor; a purge gas circulation unit, wherein the purge gas circulation unit and the seawater circulation unit are respectively located on both sides of the membrane distillation unit, the purge gas circulation unit comprising a condensation assembly and a purge assembly, the condensation assembly being used to perform multi-stage cooling on the desalted water vapor and produce condensed water for recycling, and the purge assembly being used to collect the dry cold gas discharged from the condensation assembly and pump it to the membrane distillation unit for recycling; The heat circulation unit is located between the seawater circulation unit and the condensation component. The heat circulation unit is used to transport the circulating working fluid of the condensation component to the seawater circulation unit for heat circulation utilization, and to cool and circulate the circulating working fluid after heat circulation utilization.

2. The closed-cycle desalination device according to claim 1, characterized in that: The seawater circulation unit comprises a liquid storage tank (11), a medium-temperature heater (12) and a high-temperature supplementary heater (13) which are sequentially connected through pipelines. A booster pump (16) is further provided on the pipeline between the liquid storage tank (11) and the medium-temperature heater (12). The booster pump (16) is used to increase the pressure of the seawater on the pipeline. The liquid storage tank (11) stores seawater containing inorganic salts. The medium-temperature heater (12) is used to heat the seawater discharged from the liquid storage tank (11) to a first preset temperature. The high-temperature supplementary heater (13) is provided in the membrane distillation unit and is used to heat the seawater having the first preset temperature to a membrane distillation preset temperature, wherein the membrane distillation preset temperature is greater than the first preset temperature.

3. The closed-cycle desalination device according to claim 2, characterized in that: The seawater circulation unit further comprises a make-up water circuit (L1) and a sewage circuit (L2) respectively arranged at the side end and the bottom end of the liquid storage tank (11); the make-up water circuit (L1) is provided with a first heat exchanger (14); a second heat exchanger (15) is provided on a pipeline connecting the make-up water circuit (L1) and the sewage circuit (L2); low-concentration and low-temperature seawater is heated by the first heat exchanger (14) and the second heat exchanger (15) respectively and then replenished into the liquid storage tank (11) along the make-up water circuit (L1); the sewage circuit (L2) is used to receive high-concentration seawater discharged from the liquid storage tank (11) and cool it by the second heat exchanger (15) before being discharged to the salt field.

4. The closed-cycle desalination device according to claim 3, characterized in that: The membrane distillation unit comprises a distillation body (21) and a distillation membrane (22), wherein the distillation membrane (22) is used to divide the distillation body (21) into a first cavity and a second cavity, the high-temperature supplementary heater (13) is arranged in the first cavity, and a heating humidifier (23) is arranged in the second cavity, the distillation membrane (22) is used to perform membrane distillation on the seawater heated by the high-temperature supplementary heater (13) and form desalted water vapor, and the heating humidifier (23) is used to absorb the high-temperature desalted water vapor from the inlet dry cold air to heat and humidify it into humid hot gas and transport it to the condensation component.

5. The closed-cycle desalination device according to claim 4, characterized in that: The condensation component includes a medium-temperature condenser (31) and a low-temperature condenser (32) connected by a pipeline, the inlet end of the medium-temperature condenser (31) is connected to the outlet end of the second cavity, the outlet end of the medium-temperature condenser (31) discharges condensed water through a first condensed water discharge pipeline, the medium-temperature air discharged from the medium-temperature condenser (31) enters the low-temperature condenser (32) for low-temperature condensation, and the outlet end of the low-temperature condenser (32) discharges condensed water through a second condensed water discharge pipeline. A circulation pipeline (L5) is also connected between the medium-temperature condenser (31) and the low-temperature condenser (32), and the dry cold gas discharged from the low-temperature condenser (32) can enter the medium-temperature condenser (31) for recycling.

6. The closed-cycle desalination device according to claim 5, characterized in that: The purge assembly includes a purge pipeline (L6) and a fan (41) provided on the purge pipeline (L6); the purge pipeline (L6) is connected between the medium-temperature condenser (31) and the second cavity; the fan (41) is used to allow a portion of the dry cold gas discharged from the medium-temperature condenser (31) to enter the second cavity through the purge pipeline (L6) for recycling; and another portion of the dry cold gas discharged from the medium-temperature condenser enters the low-temperature condenser through the pipeline.

7. The closed-cycle desalination device according to claim 6, characterized in that: A recovery tank (42) is further provided on the purge pipeline (L6) between the fan (41) and the distillation body (21). The recovery tank (42) is connected to the first condensed water discharge pipeline. The recovery tank (42) is used to recover the condensed water formed in the purge pipeline (L6).

8. The closed-cycle desalination device according to claim 7, characterized in that: The thermal cycle unit comprises: A compressor (51), wherein the inlet end of the compressor (51) is connected to the circulation outlet of the low-temperature condenser (32), and the superheated working fluid discharged from the outlet end of the compressor (51) passes through the high-temperature supplementary heater (13) and the medium-temperature heater (12) in sequence through a first heat circulation pipeline (L5) for pre-cooling; The supercooling component is used to supercool the circulating working fluid after pre-cooling; The throttle valve assembly throttles the circulating working fluid after the supercooling treatment and returns it to the circulation inlet of the low-temperature condenser (32).

9. The closed-cycle desalination device according to claim 8, characterized in that: The supercooling component includes: The first heat exchanger (14) performs a primary cooling of the circulating working fluid flowing out of the medium-temperature heater (12) after cooling by replenishing water with seawater; a secondary subcooler (52) for collecting condensed water discharged from the first condensed water discharge pipeline and the second condensed water discharge pipeline, and performing secondary cooling on the circulating working medium after the primary cooling by means of the condensed water; The three-stage subcooler (53) performs a third cooling on the circulating working medium after the second cooling.

10. A closed circulation system for seawater desalination, characterized in that: The device comprises an electronic control device and a seawater desalination closed circulation device according to any one of claims 1 to 9.

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