An instant heating direct contact membrane distillation system

Abstract

This invention provides a direct-contact membrane distillation system with instant heating, belonging to the field of membrane distillation. The membrane distillation system of this invention includes a feed-side component, a membrane module, and a product water-side component. The feed-side component includes an instant-heating membrane distillation heater, which is directly installed between the membrane module and the solution to be separated. The instant-heating membrane distillation heater rapidly heats the flowing solution to be separated, which then flows directly into the membrane module. This invention improves heating efficiency while minimizing heat loss during solution flow, overcoming the problems of long heating time and heat loss during transportation in existing technologies. This invention can also achieve heating of the hot side to a preset temperature by connecting multiple instant-heating membrane distillation heating devices in series. Furthermore, this invention improves the hot side of the membrane module based on the heating characteristics of the instant-heating membrane distillation heater, utilizing methods such as extending the hot side residence time or generating turbulence to increase membrane flux.

Description

Technical Field

[0001] This invention belongs to the fields of seawater desalination, ultrapure water preparation, and wastewater treatment, and specifically relates to a direct contact membrane distillation system with instant heating. Background Technology

[0002] Membrane distillation is a novel membrane separation process that has emerged in recent years. It utilizes hydrophobic microporous membranes to separate aqueous solutions containing non-volatile solutes. Due to the surface tension of water, liquid water cannot permeate the membrane's micropores at normal pressure, while water vapor can. When a temperature difference exists across the membrane, water vapor molecules permeate through the micropores and condense on the other side due to the difference in vapor pressure, gradually concentrating the solution. This process can fully utilize inexpensive energy sources such as factory heat or solar energy, and its ease of automation and simple equipment have made it a practically significant separation process. Since its introduction in 1963, this technology has been classified into four structures based on the different condensation methods of volatile components on the membrane permeate side: direct contact membrane distillation (DCMD), air-gap membrane distillation (AGMD), scavenged gas membrane distillation (SGMD), and vacuum membrane distillation (VMD).

[0003] Membrane distillation is relatively simple to implement, mainly consisting of three parts: the feed side, the membrane module, and the product water side.

[0004] On the feed side, the main components include the solution to be separated (an aqueous solution of a non-volatile solute, such as seawater, brackish water, or wastewater), heating equipment, and pumps. This part primarily heats the solution to be separated to a preset temperature and then pumps it into the membrane module.

[0005] The membrane module is the central unit of a membrane distillation system, the site where the membrane separation process takes place, and the carrier of the membrane distillation process. The quality of the membrane module structure directly affects the separation efficiency and economic performance of membrane distillation. Commonly used membrane modules in industry include plate and frame membrane modules, cylindrical membrane modules, hollow fiber membrane modules, and spiral wound membrane modules. Among these, the most important component of the membrane module is the porous hydrophobic membrane it contains. Commonly used porous hydrophobic membranes in industry include polytetrafluoroethylene (PTFE), polypropylene (PP), and polyvinylidene fluoride (PVDF), with PTFE being the most widely used.

[0006] On the product water side, it mainly includes product water pipes, pumps, condensation equipment, etc. This part is mainly responsible for condensing the steam passing through the hydrophobic porous membrane and collecting the liquefied distilled water.

[0007] The main drawbacks of existing technologies include:

[0008] (1) Regardless of the membrane distillation method or membrane module, the solution to be separated needs to be preheated and can only be started after the preset temperature is reached. The process is time-consuming, especially when the preset temperature is high.

[0009] (2) Regardless of the membrane distillation method or membrane module, the solution to be separated needs to be continuously heated after the distillation process begins in order to keep its temperature constant within the preset temperature range, which results in significant energy waste and increases the cost of water production.

[0010] (3) During the process of transporting the solution to be separated to the membrane module by the peristaltic pump, there is heat loss, resulting in energy waste.

[0011] (4) In order to protect the heating equipment of the membrane distillation system, when starting the membrane distillation system, the amount of solution to be separated needs to be greater than the safe water level of the heating equipment container, resulting in poor system application flexibility.

[0012] (5) After the membrane distillation process begins, when the water level in the heating equipment of the solution to be separated drops, it is necessary to add water in time to avoid dry burning; if no water is added, the heating equipment must be turned off and heating stopped, which will cause the water production efficiency of the subsequent membrane distillation process to decrease due to the decrease in the temperature of the solution to be separated. Summary of the Invention

[0013] To address the problems in the prior art, this invention proposes a direct contact membrane distillation system with instant heating.

[0014] The technical solution of the present invention is as follows:

[0015] This invention first discloses a direct contact membrane distillation system with instant heating, which includes a feed-side component, a membrane component, and a product water-side component. The feed-side component is used to deliver the solution to be separated to the hot side of the membrane component at a preset temperature. The membrane component uses a hydrophobic porous membrane to realize the membrane distillation process. The product water-side component condenses the vapor passing through the hydrophobic porous membrane and collects the liquefied distilled water.

[0016] The feed-side assembly is characterized by comprising a hot-side circulation pipeline, an instantaneous membrane distillation heater, a hot-side water pump for conveying the solution to be separated, and a solution tank for storing the solution to be separated; wherein the solution tank, the hot-side water pump, the instantaneous membrane distillation heater, and the hot side of the membrane assembly are sequentially connected through the hot-side circulation pipeline to form a hot-side circulation; the outlet of the instantaneous membrane distillation heater is directly connected to the hot-side inlet of the membrane assembly;

[0017] The instantaneous membrane distillation heater includes a controller and several instantaneous membrane distillation heating units with the same structure and arranged in series; an inlet temperature sensor is installed at the inlet of the instantaneous membrane distillation heater, and an outlet temperature sensor is installed at the outlet; each instantaneous membrane distillation heating unit includes an S-shaped copper tube and a heating assembly.

[0018] The S-shaped copper tube serves as the flow channel for the solution to be separated. The heating components are wrapped around the outside of the S-shaped copper tube to heat the solution to be separated. The controller is connected to the inlet temperature sensor, the outlet temperature sensor, each heating component, and the hot-side water pump. It is used to acquire temperature information, set the preset temperature, and control the switching of the heating components and / or the pumping flow rate of the hot-side water pump.

[0019] As an optional implementation, the heating assembly is made of a copper tube wrapped around the outside of an S-shaped copper tube, which contains a heating wire and is filled with magnesium oxide powder insulation material. The heating wire is encapsulated and fixed in the middle of the tube so that it does not contact the tube wall, thereby converting electrical energy into heat energy to heat the solution to be separated inside the S-shaped copper tube.

[0020] As a preferred embodiment of the present invention, the S-shaped copper tubes of the instantaneous membrane distillation heating unit are connected in series; the S-shaped copper tubes are arranged in an S-shape or serpentine shape inside the heating assembly to increase the heated tube wall area.

[0021] As a preferred embodiment of the present invention, the membrane assembly includes: an upper cover plate, a hydrophobic porous membrane, and a lower cover plate; the hydrophobic porous membrane is placed between the upper cover plate and the lower cover plate; the upper cover plate is provided with a hot-side membrane distillation evaporation tank and is provided with a hot-side outlet and a hot-side inlet communicating with the hot-side membrane distillation evaporation tank; the lower cover plate is provided with a cold-side membrane distillation condensation tank and is provided with a cold-side outlet and a cold-side inlet communicating with the cold-side membrane distillation condensation tank; the hot-side membrane distillation evaporation tank is provided with triangular protrusions to increase the turbulence of the hot-side fluid.

[0022] As a preferred embodiment of the present invention, the membrane assembly includes: an upper cover plate, a hydrophobic porous membrane, and a lower cover plate; the hydrophobic porous membrane is placed between the upper cover plate and the lower cover plate; the upper cover plate is provided with a hot-side membrane distillation evaporation tank and is provided with a hot-side outlet and a hot-side inlet communicating with the hot-side membrane distillation evaporation tank; the lower cover plate is provided with a cold-side membrane distillation condensation tank and is provided with a cold-side outlet and a cold-side inlet communicating with the cold-side membrane distillation condensation tank; the hot-side membrane distillation evaporation tank is provided with an S-shaped flow channel to increase the residence time of the hot-side fluid.

[0023] As a preferred embodiment of the present invention, the water production side assembly includes a cold-side circulation pipeline, a water production tank, a cold-side refrigeration device, and a cold-side water pump; the water production tank, the cold-side water pump, and the cold side of the membrane assembly are sequentially connected through the cold-side circulation pipeline to form a cold-side circulation; the cold-side refrigeration device is installed in the water production tank to control the temperature of the cold-side circulating liquid.

[0024] The present invention also provides a direct contact membrane distillation method with instantaneous heating of the system, comprising the following steps:

[0025] 1) Fill the solution tank with an appropriate amount of solution, select the number of instantaneous membrane distillation heating units to connect in series to form an instantaneous membrane distillation heater, and connect the instantaneous membrane distillation heater between the hot-side water pump and the membrane module; the outlet of the instantaneous membrane distillation heater is directly connected to the hot-side inlet of the membrane module.

[0026] 2) Turn on the controller and set the preset temperature, which is between 50 and 80°C;

[0027] 3) Start the hot-side water pump and adjust the pump flow rate to introduce the solution to be separated into the instantaneous membrane distillation heater; check the temperature of the solution to be separated at the outlet through the outlet temperature sensor of the instantaneous membrane distillation heater; if the temperature is lower than the preset temperature, reduce the flow rate of the water pump in the solution to be separated tank, or connect more instantaneous membrane distillation heating units in series to achieve temperature control; after the solution to be separated flows through the instantaneous membrane distillation heater, it flows directly into the membrane module;

[0028] 4) The membrane module uses a hydrophobic porous membrane to achieve membrane distillation. The product water side module will condense the vapor through the hydrophobic porous membrane and collect the liquefied distilled water.

[0029] Preferably, when the flow rate of the solution to be separated is too fast and the heating temperature on the hot side cannot reach the set value, a membrane module with an S-shaped flow channel in the hot-side membrane distillation evaporation tank is selected; otherwise, a membrane module with triangular protrusions in the hot-side membrane distillation evaporation tank is selected.

[0030] Compared with the prior art, the beneficial effects of the present invention include at least the following:

[0031] (1) To address the problems of long heating time for the solution to be separated, heat loss during transportation, and excessive energy consumption for continuous constant-temperature heating in membrane distillation, this invention provides an instantaneous membrane distillation heater. This device is directly installed between the membrane module and the solution to be separated tank. Preheating of the solution to be separated is unnecessary. When the solution to be separated flows through the device via a peristaltic pump, the device rapidly heats it and then it flows directly into the membrane module. This improves heating efficiency while minimizing heat loss during the flow process. Furthermore, multiple instantaneous membrane distillation heaters can be connected in series to heat the hot side to a preset temperature.

[0032] (2) To improve the heating efficiency during membrane distillation, this invention provides an instantaneous membrane distillation heater. The solution to be separated is circulated via a peristaltic pump through the solution tank, the peristaltic pump, the instantaneous membrane distillation module, the membrane module, and the solution tank. When the water level in the solution tank is too low to continue circulation, the membrane distillation process stops, and the instantaneous membrane distillation module automatically stops heating. The instantaneous membrane module is equipped with a temperature control device to adjust the temperature. When the temperature is too high, the system automatically stops heating, eliminating the risk of heater dry burning or damage.

[0033] (3) Due to the use of an instantaneous membrane distillation heater, the hot-side temperature may fail to reach the set value when the hot-side flow rate is set too high. To meet the control requirements of different solutions to be separated, a membrane distillation assembly with an S-shaped flow channel on the hot side and a membrane distillation assembly with a triangular protrusion on the hot side were designed. The membrane distillation assembly with an S-shaped flow channel on the hot side extends the passage time of the solution to be separated on the hot side without changing the contact area between the hot and cold sides. It is suitable for the condition where the temperature cannot reach the preset value due to the high hot-side flow rate, which is beneficial to increasing the membrane flux. The membrane distillation assembly with a triangular protrusion on the hot side generates turbulence when the solution to be separated flows through the hot side, which promotes the evaporation of the solution to be separated. It is suitable for the condition where the hot-side flow rate is low and the temperature is controllable, which is beneficial to increasing the membrane flux. Attached Figure Description

[0034] Figure 1 This is a schematic diagram of the direct contact membrane distillation system with instant heating according to the present invention.

[0035] Figure 2 This is a three-dimensional structural diagram of an instantaneous membrane distillation heater;

[0036] Figure 3 This is a two-dimensional structural diagram of an instantaneous membrane distillation heater;

[0037] Figure 4 A three-dimensional structural diagram of a membrane distillation assembly with triangular protrusions on the hot side;

[0038] Figure 5 A three-dimensional structural diagram of a membrane distillation assembly with an S-shaped flow channel on the hot side;

[0039] Figure 6 A schematic diagram of a membrane distillation assembly with a triangular protrusion on the hot side connected to an instantaneous membrane distillation heater;

[0040] Figure 7 A schematic diagram of a membrane distillation assembly with an S-shaped flow channel on the hot side connected to an instantaneous membrane distillation heater;

[0041] In the diagram: 1. Instantaneous membrane distillation heater; 2. Hot-side water pump; 3. Solution tank to be separated; 4. Membrane module; 5. Product water balance; 6. Product water tank; 7. Cold-side refrigeration unit; 8. Cold-side water pump; 9. Inlet temperature sensor; 10. S-shaped copper tube inlet; 11. Heating assembly; 12. Controller; 13. S-shaped copper tube outlet; 14. Outlet temperature sensor; 15. Housing; 16. Membrane distillation module with triangular protrusion on the hot side; 17. Top cover plate; 18. Hot-side outlet; 19. Hot side... 19. Inlet; 20. Triangular protrusion; 21. Hot-side membrane distillation evaporation tank; 22. Lower cover plate; 23. Cold-side outlet; 24. Cold-side inlet; 25. Cold-side membrane distillation condenser; 26. Membrane distillation assembly with S-shaped flow channel on the hot side; 27. Upper cover plate; 28. Hot-side outlet; 29. ​​Hot-side inlet; 30. S-shaped flow channel; 31. Hot-side membrane distillation evaporation tank; 32. Lower cover plate; 33. Cold-side outlet; 34. Cold-side inlet; 35. Cold-side membrane distillation condenser. Detailed Implementation

[0042] The present invention will be further described and illustrated below with reference to specific embodiments. The embodiments described are merely examples of the content of this disclosure and do not limit the scope of the invention. The technical features of each embodiment in the present invention can be combined accordingly, provided that there is no mutual conflict.

[0043] like Figure 1-3 As shown, this embodiment provides a direct contact membrane distillation system with instant heating, which includes a feed-side component, a membrane module 4, and a product water-side component. The feed-side component is used to deliver the solution to be separated to the hot side of the membrane module at a preset temperature. The membrane module 4 uses a hydrophobic porous membrane to realize the membrane distillation process. The product water-side component condenses the vapor passing through the hydrophobic porous membrane and collects the liquefied distilled water.

[0044] like Figure 1 As shown, the feed-side assembly includes a hot-side circulation pipeline, an instantaneous membrane distillation heater 1, a hot-side water pump 2 for conveying the solution to be separated, and a solution tank 3 for storing the solution to be separated. The solution tank 3, the hot-side water pump 2, the instantaneous membrane distillation heater 1, and the membrane module 4 are sequentially connected via the hot-side circulation pipeline to form a hot-side circulation system. The outlet of the instantaneous membrane distillation heater 1 is directly connected to the hot-side inlet of the membrane module 4. The instantaneous membrane distillation heater 1 is installed between the hot-side water pump 2 and the membrane module 4 to heat the solution to be separated. The heating performance of this equipment can be controlled by the controller 12. After the system starts, the solution to be separated is drawn by the hot-side water pump 2 and flows into the instantaneous membrane distillation heater 1 for rapid heating, and then directly into the membrane module 4. The instantaneous membrane distillation heater 1 is directly connected to the inlet of the membrane module 4 on the separation side, minimizing heat loss of the solution during transportation and improving thermal efficiency and energy utilization.

[0045] like Figure 1 As shown, the water production side assembly includes a cold-side circulation pipeline, a water production tank 6, a cold-side refrigeration device 7, and a cold-side water pump 8. The water production tank 6, the cold-side water pump 8, and the cold side of the membrane assembly 4 are sequentially connected through the cold-side circulation pipeline to form a cold-side circulation system. The cold-side refrigeration device 7 is installed in the water production tank 6 to control the temperature of the circulating liquid on the cold side. The cold-side refrigeration device 7 can use semiconductor elements for cooling. In addition, a water production balance 5 can be installed to measure the amount of water produced in the water production tank 6.

[0046] like Figure 2 and 3 As shown, in a specific embodiment of the present invention, the instantaneous membrane distillation heater 1 includes a controller 12, a housing 15, and several instantaneous membrane distillation heating units with the same structure and arranged in series; an inlet temperature sensor 9 is provided at the inlet 10 of the instantaneous membrane distillation heater, and an outlet temperature sensor 14 is provided at the outlet 13; the housing 15 of the instantaneous membrane distillation heater 1 can be removed for maintenance, upkeep and cleaning.

[0047] Each instantaneous membrane distillation heating unit includes an S-shaped copper tube and a heating assembly 11. The S-shaped copper tube serves as the flow channel for the solution to be separated. The heating assembly 11 is wrapped around the outside of the S-shaped copper tube to heat the solution. The controller 12 is connected to the inlet temperature sensor 9, the outlet temperature sensor 14, each heating assembly 11, and the hot-side water pump 2. It is used to acquire temperature information, set preset temperatures, and control the switching of the heating assembly and / or the pumping flow rate of the hot-side water pump. The heating assembly is made of a thinner copper tube wrapped around the outside of the S-shaped copper tube. It contains a heating wire and is filled with magnesium oxide powder insulation material. The heating wire is encapsulated and fixed in the middle of the tube so that it does not contact the tube wall, thus converting electrical energy into internal energy to heat the solution to be separated inside the S-shaped copper tube. The S-shaped copper tubes of the instantaneous membrane distillation heating unit are connected in series. The S-shaped copper tubes are arranged in an S-shape or serpentine pattern inside the heating assembly to increase the heated tube wall area.

[0048] like Figure 4 , 5 As shown, two types of membrane modules are available for different operating conditions: a membrane distillation module 16 with triangular protrusions on the hot side and a membrane distillation module 26 with an S-shaped flow channel on the hot side. The membrane module includes: an upper cover plate 17 / 27, a hydrophobic porous membrane, and a lower cover plate 22 / 32. The hydrophobic porous membrane is placed between the upper and lower cover plates. The upper cover plate contains a hot-side membrane distillation evaporation tank 21 / 31, with a hot-side outlet 18 / 28 and a hot-side inlet 19 / 29 connected to the hot-side membrane distillation evaporation tank. The lower cover plate contains a cold-side membrane distillation condensation tank 25 / 35, with a cold-side outlet 23 / 33 and a cold-side inlet 24 / 34 connected to the cold-side membrane distillation condensation tank.

[0049] like Figure 4 As shown, the hot-side membrane distillation evaporation tank 21 is provided with triangular protrusions 20 to increase the turbulence of the hot-side fluid. A hydrophobic porous membrane is placed between the upper cover plate 17 and the lower cover plate 22 of this component, and is equipped with several arbitrary rubber sealing rings. The upper and lower cover plates are connected by several bolts to ensure the sealing performance during equipment operation.

[0050] like Figure 5 As shown, the hot-side membrane distillation evaporation tank is equipped with an S-shaped flow channel to increase the residence time of the hot-side fluid. A hydrophobic porous membrane is placed between the upper cover plate 27 and the lower cover plate 32 of the assembly, and is fitted with several rubber sealing rings. The upper and lower cover plates are connected by several bolts to ensure airtightness during equipment operation.

[0051] When the flow rate of the solution to be separated is set relatively high, if a single instantaneous membrane distillation heater cannot meet the membrane distillation set temperature, multiple instantaneous membrane distillation heaters can be connected in series, such as... Figure 2 , 3 As shown, the controller 12 heats the solution to be separated to a preset temperature. When the temperature and flow rate of the solution to be separated are controllable, as... Figure 6 As shown, a membrane distillation assembly 16 with triangular protrusions on the hot side is selected. Turbulence is generated by any number of triangular protrusions on the hot side, which accelerates the evaporation efficiency of the solution to be separated, reduces the risk of membrane fouling, and increases the membrane distillation flux.

[0052] When the flow rate of the solution to be separated is set relatively high, if the existing multiple instantaneous membrane distillation heaters connected in series cannot meet the membrane distillation set temperature, such as... Figure 7 As shown, a membrane distillation module 26 with an S-shaped flow channel on the hot side is selected. Without increasing the contact area between the hot and cold sides of the evaporation tank, the membrane flux is increased by increasing the residence time of the solution to be separated on the hot side.

[0053] The hot-side water pump 2 and the cold-side water pump 8 of the present invention can be selected as peristaltic pumps.

[0054] The entire operation process of this invention is as follows:

[0055] (1) Fill the solution pool with an appropriate amount of solution.

[0056] (2) Connect the instantaneous membrane distillation heater between the water pump and the membrane module of the solution to be separated in the system.

[0057] (3) Turn on the instantaneous membrane distillation heater controller and set the temperature (usually set at 50-80℃).

[0058] (4) Start the water pump of the solution to be separated tank, adjust the water pump flow rate, and introduce the solution to be separated into the instantaneous membrane distillation heater.

[0059] (5) The temperature of the solution to be separated at the outlet can be viewed through the temperature sensor of the instantaneous membrane distillation heater; if the temperature is lower than the preset temperature, the flow rate of the water pump in the solution to be separated pool can be appropriately reduced, or multiple instantaneous membrane distillation heaters can be connected in series to achieve temperature control.

[0060] (6) Select the membrane distillation assembly according to the actual working conditions. When the flow rate of the solution to be separated is set to be fast, and the existing multiple instantaneous membrane distillation heaters connected in series cannot meet the membrane distillation set temperature, select the membrane distillation assembly with an S-shaped flow channel on the hot side; otherwise, the membrane distillation assembly with a triangular protrusion on the hot side is selected by default.

[0061] (7) After the solution to be separated flows through the instantaneous membrane distillation heater, it flows directly into the membrane module.

[0062] (8) No continuous water supply to the solution tank to be separated is required throughout the process. When the water level in the solution tank to be separated is too low and the water pump cannot supply water continuously, the instantaneous membrane distillation heater can be turned off and the water pump can be turned off.

[0063] The entire membrane distillation system can replenish water to the solution tank at any time.

[0064] This invention utilizes an instant heating method, eliminating the preheating process before starting the membrane distillation system and reducing the preparation time. It also eliminates the energy waste of maintaining a constant temperature for a large volume of solution to be separated during operation. The instant heating method is directly connected to the inlet of the membrane module, reducing heat loss during flow and improving energy efficiency. Furthermore, by connecting this device in series, temperature control of the solution to be separated can be achieved to accommodate different flow rate settings.

[0065] This invention requires only rapid heating of a small amount of water, reducing the required volume of the solution to be separated for starting the membrane distillation system and improving the flexibility of its application. Utilizing an instant heating method, it eliminates the need for real-time monitoring of the solution level, enabling continuous operation and improving work efficiency.

[0066] This invention designs two membrane distillation modules with different structures for different operating conditions. When the flow rate of the solution to be separated is set relatively high, and existing multiple instantaneous membrane distillation heaters connected in series cannot meet the membrane distillation set temperature, a membrane distillation module with an S-shaped flow channel on the hot side is selected; otherwise, a membrane distillation module with a triangular protrusion on the hot side is selected by default. Both can effectively promote the membrane distillation flux.

[0067] The above-described embodiments are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. Those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention.

Claims

1. An instantaneous heating direct contact membrane distillation method for an instantaneous heating direct contact membrane distillation system, the system comprising a feed-side component, a membrane module, and a product water-side component; the feed-side component is used to deliver the solution to be separated to the hot side of the membrane module at a preset temperature, the membrane module utilizes a hydrophobic porous membrane to realize the membrane distillation process, and the product water-side component condenses the vapor passing through the hydrophobic porous membrane and collects the liquefied distilled water; Its features are, The feed-side assembly includes a hot-side circulation pipeline, an instantaneous membrane distillation heater, a hot-side water pump for conveying the solution to be separated, and a solution tank for storing the solution to be separated; wherein, the solution tank, the hot-side water pump, the instantaneous membrane distillation heater, and the hot side of the membrane module are sequentially connected through the hot-side circulation pipeline to form a hot-side circulation; the outlet of the instantaneous membrane distillation heater is directly connected to the hot-side inlet of the membrane module; The instantaneous membrane distillation heater includes a controller and several instantaneous membrane distillation heating units with the same structure and arranged in series; an inlet temperature sensor is installed at the inlet of the instantaneous membrane distillation heater, and an outlet temperature sensor is installed at the outlet; each instantaneous membrane distillation heating unit includes an S-shaped copper tube and a heating assembly. The S-shaped copper tube serves as the flow channel for the solution to be separated. The heating components are wrapped around the outside of the S-shaped copper tube to heat the solution to be separated. The controller is connected to the inlet temperature sensor, the outlet temperature sensor, each heating component, and the hot-side water pump. It is used to acquire temperature information and set the preset temperature, and to control the switching of the heating components and / or the pumping flow rate of the hot-side water pump. The heating assembly is made of a copper tube wrapped around the outside of an S-shaped copper tube. It contains a heating wire and is filled with magnesium oxide powder insulation material. The heating wire is encapsulated and fixed in the middle of the tube so that it does not contact the tube wall, thus converting electrical energy into heat energy to heat the solution to be separated inside the S-shaped copper tube. The method includes the following steps: 1) Fill the solution tank with an appropriate amount of solution, select the number of instantaneous membrane distillation heating units to connect in series to form an instantaneous membrane distillation heater, and connect the instantaneous membrane distillation heater between the hot-side water pump and the membrane module; the outlet of the instantaneous membrane distillation heater is directly connected to the hot-side inlet of the membrane module. 2) Turn on the controller and set the preset temperature, which is between 50 and 80°C; 3) Start the hot-side water pump and adjust the pump flow rate to introduce the solution to be separated into the instantaneous membrane distillation heater; check the temperature of the solution to be separated at the outlet through the outlet temperature sensor of the instantaneous membrane distillation heater; if the temperature is lower than the preset temperature, reduce the flow rate of the water pump in the solution to be separated tank, or connect more instantaneous membrane distillation heating units in series to achieve temperature control; after the solution to be separated flows through the instantaneous membrane distillation heater, it flows directly into the membrane module; 4) The membrane module utilizes a hydrophobic porous membrane to achieve membrane distillation. The product water side module will condense the vapor passing through the hydrophobic porous membrane and collect the liquefied distilled water. When the flow rate of the solution to be separated is too fast and the heating temperature on the hot side cannot reach the set value, a membrane module with an S-shaped flow channel in the hot-side membrane distillation evaporation tank should be selected; otherwise, a membrane module with triangular protrusions in the hot-side membrane distillation evaporation tank should be selected.

2. The instantaneous heating direct contact membrane distillation method according to claim 1, characterized in that, The S-shaped copper tubes of the instantaneous membrane distillation heating unit are connected in series; the S-shaped copper tubes are arranged in an S-shape or serpentine shape inside the heating component to increase the heated tube wall area.

3. The instantaneous heating direct contact membrane distillation method according to claim 1, characterized in that, The membrane assembly includes: an upper cover plate, a hydrophobic porous membrane, and a lower cover plate; the hydrophobic porous membrane is placed between the upper cover plate and the lower cover plate; the upper cover plate has a hot-side membrane distillation evaporation tank and is provided with a hot-side outlet and a hot-side inlet connected to the hot-side membrane distillation evaporation tank; the lower cover plate has a cold-side membrane distillation condensation tank and is provided with a cold-side outlet and a cold-side inlet connected to the cold-side membrane distillation condensation tank; the hot-side membrane distillation evaporation tank is provided with triangular protrusions to increase the turbulence of the hot-side fluid.

4. The instantaneous heating direct contact membrane distillation method according to claim 1, characterized in that, The membrane assembly includes: an upper cover plate, a hydrophobic porous membrane, and a lower cover plate; the hydrophobic porous membrane is placed between the upper cover plate and the lower cover plate; the upper cover plate has a hot-side membrane distillation evaporation tank and is provided with a hot-side outlet and a hot-side inlet connected to the hot-side membrane distillation evaporation tank; the lower cover plate has a cold-side membrane distillation condensation tank and is provided with a cold-side outlet and a cold-side inlet connected to the cold-side membrane distillation condensation tank; the hot-side membrane distillation evaporation tank is provided with an S-shaped flow channel to increase the residence time of the hot-side fluid.

5. The instantaneous heating direct contact membrane distillation method according to claim 1, characterized in that, The water production side assembly includes a cold-side circulation pipeline, a water production tank, a cold-side refrigeration device, and a cold-side water pump; the water production tank, the cold-side water pump, and the cold side of the membrane module are connected sequentially through the cold-side circulation pipeline to form a cold-side circulation; the cold-side refrigeration device is installed in the water production tank to control the temperature of the cold-side circulating liquid.

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