Dual-stage non-contact membrane distillation wastewater treatment device and treatment method thereof

Abstract

The application discloses a two-stage non-contact membrane distillation wastewater treatment device and a treatment method thereof. The wastewater treatment device comprises an evaporation tower, a first membrane distillation assembly, a second membrane distillation assembly, a first fan, a second fan, an evaporation heat exchange assembly, a temperature and humidity adjusting assembly, a cyclone water separator and a heating assembly. The evaporation tower, the first membrane distillation assembly, the first fan, the second membrane distillation assembly, the second fan, the evaporation heat exchange assembly, the temperature and humidity adjusting assembly and the cyclone water separator are sequentially connected in order. The cyclone water separator is further connected with the evaporation tower through the second membrane distillation assembly and the first membrane distillation assembly. The first membrane distillation assembly is arranged in the evaporation tower and located at the top of the evaporation tower. The heating assembly is connected with the evaporation tower and used for heating and treating radioactive wastewater in the evaporation tower. The application is used for highly reducing the volume and deeply purifying radioactive wastewater generated in nuclear power station operation and maintenance, nuclear accident emergency, spent fuel reprocessing plant production, hospital radiotherapy and the like.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of water treatment, in particular to a two-stage non-contact membrane distillation wastewater treatment device and a treatment method thereof. BACKGROUND

[0002] A large amount of radioactive wastewater is generated in the fields of nuclear power plant operation and maintenance, nuclear accident emergency treatment, spent fuel reprocessing plant production, hospital radiotherapy, etc. In order to protect environmental safety and public health and shorten the process of radioactive wastewater treatment, such wastewater needs to be efficiently, economically and effectively reduced and purified. At present, the treatment methods of radioactive wastewater in traditional technologies mainly include filtration, ion exchange, evaporation concentration, adsorption, biological treatment or a combination of these processes. However, most of the above treatment methods have complex system settings, high energy consumption, large amount of solid waste, and high investment, operation and maintenance costs.

[0003] Among them, the membrane distillation technology utilizes the characteristics that only water vapor and other volatile components can pass through the membrane pores by means of hydrophobic microporous membranes, and the membrane separation process is driven by the pressure difference of gas molecules on both sides of the membrane. In the membrane distillation process, a proper temperature difference is maintained on both sides of the membrane, so the membrane distillation technology has the advantages of simple device, mild operating conditions, good purification effect, etc., and can be widely used in wastewater treatment, concentration, purification, etc. However, in the traditional membrane distillation technology, the wastewater is in direct contact with the membrane, which easily causes membrane pollution, membrane pore blockage and membrane hydrophilization, etc., resulting in short service life of the membrane, low and unstable flux, easy breakage of the membrane and difficulty in online detection, etc. In addition, the membrane distillation technology needs to maintain a large temperature difference on both sides of the membrane, which has the problem of high energy consumption. Therefore, the traditional membrane distillation technology is also difficult to meet the actual production needs. Further, for the wastewater generated in the hospital nuclear medicine department, etc., which is difficult to purify, a single membrane distillation purification treatment often cannot meet the actual needs. SUMMARY

[0004] Therefore, it is necessary to provide a two-stage non-contact membrane distillation wastewater treatment device. The two-stage non-contact membrane distillation wastewater treatment device can meet the needs of the nuclear medicine department, nuclear power plant, spent fuel processing plant, etc. for the treatment of radioactive wastewater.

[0005] An embodiment of the present application provides a two-stage non-contact membrane distillation wastewater treatment device.

[0006] A double-stage non-contact membrane distillation wastewater treatment device, comprising an evaporation tower, a first membrane distillation assembly, a second membrane distillation assembly, a first fan, a second fan, an evaporation heat exchange assembly, a temperature and humidity adjusting assembly, a cyclone water separator, and a heating assembly, the evaporation tower, the first membrane distillation assembly, the first fan, the second membrane distillation assembly, the second fan, the evaporation heat exchange assembly, the temperature and humidity adjusting assembly, and the cyclone water separator are sequentially connected in order, the cyclone water separator is further connected to the evaporation tower through the second membrane distillation assembly and the first membrane distillation assembly, the first membrane distillation assembly is arranged in the evaporation tower and close to the top of the evaporation tower, the heating assembly and the shell and tube heat exchanger of a heat pump system are connected to the evaporation tower for heating treatment of radioactive wastewater in the evaporation tower, the first fan is used to assist diffusion of high-humidity gas in the evaporation tower through the first membrane distillation assembly, the second fan is used to assist diffusion of high-humidity gas from the first membrane distillation assembly through the second membrane distillation assembly, the evaporation heat exchange assembly is used to exchange heat of high-temperature water vapor from the second fan, the temperature and humidity adjusting assembly is used to cool low-temperature water vapor after heat exchange of the evaporation heat exchange assembly, and the cyclone water separator is used to separate low-temperature water vapor from the temperature and humidity adjusting assembly to produce secondary purified liquid, and dry and cold air after separation of the cyclone water separator is input into the second membrane distillation assembly and the first membrane distillation assembly for circulation.

[0007] In some embodiments, the double-stage non-contact membrane distillation wastewater treatment device further comprises a flow sensor arranged on a circulation pipeline between the second membrane distillation assembly and the second fan to detect the flow of high-temperature water vapor in the circulation pipeline.

[0008] In some embodiments, the double-stage non-contact membrane distillation wastewater treatment device further comprises a first temperature and humidity sensor arranged on a circulation pipeline between the second membrane distillation assembly and the second fan to detect the temperature and humidity of high-temperature water vapor in the circulation pipeline.

[0009] In some embodiments, the double-stage non-contact membrane distillation wastewater treatment device further comprises a second temperature and humidity sensor arranged on a circulation pipeline between the second membrane distillation assembly and the second fan to detect the temperature and humidity of high-temperature water vapor in the circulation pipeline.

[0010] In some embodiments, the double-stage non-contact membrane distillation wastewater treatment device further comprises a gas supplement pipeline connected to a circulation pipeline between the second membrane distillation assembly and the second fan, and a gas supplement valve installed on the gas supplement pipeline to supplement gas into the circulation pipeline between the evaporation tower and the second fan.

[0011] In some embodiments, the double-stage non-contact membrane distillation wastewater treatment device further comprises a pressure sensor arranged on a circulation pipeline between the cyclone water separator and the second membrane distillation assembly for detecting the pressure of the dry cold air in the circulation pipeline.

[0012] In some embodiments, the double-stage non-contact membrane distillation wastewater treatment device further comprises a third temperature and humidity sensor arranged on a circulation pipeline between the cyclone water separator and the second membrane distillation assembly for detecting the temperature and humidity of the dry cold air in the circulation pipeline.

[0013] In some embodiments, the double-stage non-contact membrane distillation wastewater treatment device further comprises a first purified liquid outlet pipeline connected to the second membrane distillation assembly for discharging the first purified liquid separated by the second membrane distillation assembly, and a first purified liquid outlet valve installed on the first purified liquid outlet pipeline.

[0014] In some embodiments, the double-stage non-contact membrane distillation wastewater treatment device further comprises a second purified liquid outlet pipeline connected to the cyclone water separator for discharging the second purified liquid separated by the cyclone water separator, and a second purified liquid outlet valve installed on the second purified liquid outlet pipeline.

[0015] In some embodiments, the double-stage non-contact membrane distillation wastewater treatment device further comprises a compressor, a shell-and-tube heat exchanger, and a wastewater circulating pump. The evaporation tower, the heating assembly, and the shell-and-tube heat exchanger are connected in circulation through a heating pipeline, the wastewater circulating pump is installed on the heating pipeline, and the wastewater circulating pump is used to realize heat exchange of the radioactive wastewater in the evaporation tower through the shell-and-tube heat exchanger and heating through the heating assembly.

[0016] The shell-and-tube heat exchanger is further connected in circulation with the evaporation heat exchange assembly through a heat pump system pipeline, the compressor is installed on the heat pump system pipeline, the heat pump system pipeline is provided with a refrigerant, the refrigerant passes through the evaporation heat exchange assembly to realize heat exchange of the high-temperature water vapor in the evaporation heat exchange assembly to absorb the heat of the high-temperature water vapor, and the compressor is used to realize change of the refrigerant in the heat pump system pipeline from normal temperature and pressure to high temperature and high pressure, and then input the shell-and-tube heat exchanger to exchange heat with the radioactive wastewater in the shell-and-tube heat exchanger to improve the heating efficiency.

[0017] In some embodiments, the double-stage non-contact membrane distillation wastewater treatment device further comprises a spiral nozzle installed in the evaporation tower and close to the lower side of the first membrane distillation assembly, the spraying direction of the spiral nozzle is downward to the bottom of the evaporation tower, and the spiral nozzle is connected to a heating pipe extending into the evaporation tower.

[0018] In some embodiments, the double-stage non-contact membrane distillation wastewater treatment device further satisfies at least one of the following conditions:

[0019] (1) The double-stage non-contact membrane distillation wastewater treatment device further comprises a makeup water pump installed on the liquid inlet pipe of the evaporation tower for pumping the radioactive wastewater to be treated;

[0020] (2) The first membrane distillation assembly comprises a hydrophobic membrane;

[0021] (3) The second membrane distillation assembly comprises a hydrophobic membrane;

[0022] (4) The double-stage non-contact membrane distillation wastewater treatment device further comprises a wastewater temporary storage tank connected to the evaporation tower through a liquid inlet pipe;

[0023] (5) The double-stage non-contact membrane distillation wastewater treatment device further comprises a blowdown valve installed at the blowdown port of the bottom of the evaporation tower.

[0024] An embodiment of the present application provides a double-stage non-contact membrane distillation wastewater treatment method.

[0025] A double-stage non-contact membrane distillation wastewater treatment method, which adopts the double-stage non-contact membrane distillation wastewater treatment device described above, comprises the following steps:

[0026] The radioactive wastewater is input into the evaporation tower to a preset height;

[0027] The heating assembly is controlled to heat the radioactive wastewater in the evaporation tower to a preset temperature;

[0028] The radioactive wastewater in the evaporation tower is diffused to the hot side of the first membrane distillation assembly in the form of high-humidity gas higher than the preset temperature through evaporation, and the water molecules in the high-humidity gas enter the cold side through the hydrophobic membrane in the first membrane distillation assembly under the action of pressure to form high-temperature water vapor lower than the preset temperature by 10-20℃, which is delivered to the second membrane distillation assembly through the first fan through the circulating pipe for secondary membrane distillation purification;

[0029] The water molecules in the high-humidity gas enter the cold side through the hydrophobic membrane in the second membrane distillation assembly under the action of pressure, and the high-temperature water vapor formed is transported to the evaporative heat exchange assembly by the circulating pipeline through the second fan for heat exchange to form low-temperature water vapor below 45°C and condense into purified water, and the first-stage purified liquid generated by the second membrane distillation assembly is discharged;

[0030] The low-temperature water vapor after heat exchange in the evaporative heat exchange assembly is subjected to cooling treatment by the temperature and humidity adjusting assembly, and the low-temperature water vapor from the temperature and humidity adjusting assembly is separated by the cyclone water separator to produce second-stage purified liquid, and the dry and cold air after separation of the cyclone water separator is circulated through the second membrane distillation assembly, the first membrane distillation assembly and the evaporative tower.

[0031] In some embodiments, the two-stage non-contact membrane distillation wastewater treatment method further satisfies at least one of the following conditions:

[0032] (1) The circulation of the refrigerant in the heat pump system pipeline is controlled to realize heat exchange between the refrigerant and the high-temperature water vapor in the evaporative heat exchange assembly to form low-temperature water vapor, realize heat recovery, improve the COP of the high-temperature heat pump and reduce energy consumption;

[0033] (2) The compressor is controlled to change the refrigerant in the heat pump system pipeline from normal temperature and pressure to high temperature and pressure by mechanical movement, and then deliver it to the shell-and-tube heat exchanger and exchange heat with the radioactive wastewater in the shell-and-tube heat exchanger to improve the heating efficiency of the radioactive wastewater and improve the COP of the high-temperature heat pump and reduce energy consumption;

[0034] (3) The radioactive nuclides in the radioactive wastewater include but are not limited to 133 Cs, 131 I, 89 Sr, 99 mTr, 60 Co; and the concentration of the radioactive nuclides in the radioactive wastewater is not less than 5×10 6 Bq / L;

[0035] (4) The concentration of the radioactive nuclides in the first-stage purified liquid can be reduced to 25 Bq / L~300 Bq / L;

[0036] (5) The concentration of the radioactive nuclides in the second-stage purified liquid can be reduced to 20 Bq / L~25 Bq / L.

[0037] In the aforementioned two-stage non-contact membrane distillation wastewater treatment device, a high membrane flux can be achieved without a large temperature difference between the hot and cold sides of the first and second membrane distillation modules, resulting in low energy consumption requirements for maintaining the temperature difference between the two sides of the first and second membrane distillation modules. The first and second blowers increase the gas circulation speed within the circulation pipeline and also have a purging effect on the hydrophobic membrane surfaces of the first and second membrane distillation modules, keeping the hydrophobic membranes clean, less prone to fouling, eliminating the risk of membrane damage, reducing problems such as membrane hydrophilization and corrosion, extending the service life of the hydrophobic membranes, and enhancing the overall durability of the equipment. The aforementioned two-stage non-contact membrane distillation wastewater treatment device effectively removes pollutants from wastewater... 3 This application possesses highly efficient purification capabilities for non-volatile nuclides, ions, and molecules outside of H. By employing a first membrane distillation unit and a second membrane distillation unit in conjunction, and through secondary membrane distillation purification, it can be used to treat difficult-to-purify wastewater generated by hospital nuclear medicine departments. The radioactive nuclides in the radioactive wastewater that this application can treat include, but are not limited to, those... 133 Cs、 131 I, 89 Sr、 99 mTr、 60 Co can reduce the concentration of radionuclides to 5 × 10⁻⁶. 6 Bq / L contains 131 The nuclear wastewater purification method described in this application produces purified water with a radionuclide concentration of less than 20 Bq / L to 25 Bq / L. This application can be used not only for the high-volume reduction and deep purification of radioactive wastewater generated during nuclear power plant operation and maintenance, nuclear accident emergency response, spent fuel reprocessing plant production, and hospital radiotherapy, but also for seawater desalination and ultrapure water production.

[0038] The above-mentioned two-stage non-contact membrane distillation wastewater treatment device realizes the heat recovery function of high-temperature water vapor through a heat exchange circuit composed of a shell and tube heat exchanger, an evaporation heat exchange component, and a compressor. The recovered heat is used to heat the radioactive wastewater, further reducing energy consumption requirements.

[0039] The aforementioned two-stage non-contact membrane distillation wastewater treatment device is equipped with a variety of sensors, such as a flow sensor, a first temperature and humidity sensor, a second temperature and humidity sensor, a pressure sensor, and a third temperature and humidity sensor, which can monitor the operational stability of the equipment in real time and ensure the reliability of the equipment during long-term operation.

[0040] The aforementioned two-stage non-contact membrane distillation wastewater treatment device, by setting up a drain valve, periodically discharges the concentrated wastewater in the evaporation tower, keeping the radioactivity concentration of the wastewater in the evaporation tower at a reasonable level and ensuring the effectiveness of wastewater purification during operation. Attached Figure Description

[0041] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed to be used in the embodiments description will be briefly introduced. Obviously, the drawings in the following description only constitute some embodiments of the present application, and other drawings can be obtained by those skilled in the art without paying creative labor on the basis of these drawings.

[0042] In order to more completely understand the present application and its beneficial effects, the following will be described in conjunction with the drawings. In the following description, the same reference numbers represent the same parts.

[0043] Figure 1 The schematic diagram of the two-stage non-contact membrane distillation wastewater treatment device according to an embodiment of the present application.

[0044] Explanation of reference signs

[0045] 10, two-stage non-contact membrane distillation wastewater treatment device; 100, evaporation tower; 210, first membrane distillation assembly; 220, second membrane distillation assembly; 310, first fan; 320, second fan; 400, evaporation heat exchange assembly; 500, temperature and humidity adjusting assembly; 600, cyclone water separator; 700, heating assembly; 800, flow sensor; 910, first temperature and humidity sensor; 920, second temperature and humidity sensor; 1000, air supplement valve; 1100, pressure sensor; 1200, third temperature and humidity sensor; 1310, first-stage purified liquid outlet valve; 1320, second-stage purified liquid outlet valve; 1400, compressor; 1500, shell-and-tube heat exchanger; 1600, wastewater circulating pump; 1700, spiral spray head; 1800, water supplement pump; 1900, blowdown valve; 101, circulating pipeline; 102, heat pump system pipeline; 103, heating pipeline; 104, air supplement pipeline; 105, liquid inlet pipeline. DETAILED DESCRIPTION

[0046] In order to make the above objectives, features and advantages of the present application more apparent and comprehensible, the specific embodiments of the present application will be described in detail below in conjunction with the drawings. In the following description, a lot of specific details are set forth in order to fully understand the present application. However, the present application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without departing from the connotation of the present application, so the present application is not limited by the specific embodiments disclosed below.

[0047] In the description of the application, it needs to be understood that the orientation or positional relationship indicated by the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like is based on the orientation or positional relationship shown in the drawings, which is only for the convenience of describing the application and simplifying the description, and does not indicate or imply that the device or element indicated must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation of the application.

[0048] In the present application, unless otherwise explicitly specified and limited, the terms "mounting", "connecting", "connecting", "fixing" and the like should be understood broadly, for example, it can be fixed connection, or detachable connection, or integral; it can be mechanical connection, or electrical connection; it can be direct connection, or indirect connection through intermediate medium, it can be the internal communication of two elements or the interaction relationship of two elements, unless otherwise explicitly limited. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0049] In the present application, unless otherwise explicitly specified and limited, the first feature is "on" or "under" the second feature, which can be direct contact between the first and second features, or indirect contact between the first and second features through intermediate medium. Moreover, the first feature "above", "above" and "above" the second feature can be directly above or obliquely above the first feature, or only indicate that the horizontal height of the first feature is higher than that of the second feature. The first feature "below", "below" and "below" the second feature can be directly below or obliquely below the first feature, or only indicate that the horizontal height of the first feature is less than that of the second feature.

[0050] In the description of the application, if the meaning of several is more than one, the meaning of multiple is more than two, greater than, less than, more than, etc. are not included in the number, above, below, etc. are understood to include the number. If it is described that the first, second is only used for the purpose of distinguishing technical features, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of indicated technical features or implicitly indicating the sequence of indicated technical features.

[0051] In the present document, "optionally", "optional" or "alternatively" means optional, i.e. selected from either of the two alternatives "yes" or "no". If there are multiple "optionally" in a technical solution, each "optionally" is independent of each other, unless otherwise specified, and there is no contradiction or mutual restriction. In the present application, "optionally contains" or the like means "contains or does not contain". "Optional component X" means that component X exists or does not exist, or means that the component X is contained or not contained.

[0052] In the present application, with respect to a numerical interval (i.e. a numerical range), unless otherwise specified, the distribution of optional values in the numerical interval is considered to be continuous, and includes both numerical endpoints (i.e. the minimum value and the maximum value) of the numerical interval, and each numerical value between the two numerical endpoints. Unless otherwise specified, when a numerical interval only points to integers in the numerical interval, including both endpoint integers of the numerical range and each integer between the two endpoints, it is equivalent to directly listing each integer. When multiple numerical ranges are provided to describe a feature or a characteristic, these numerical ranges can be combined. In other words, unless otherwise specified, the numerical ranges disclosed in the present application should be understood to include any and all sub-ranges included therein. The "numerical value" in the numerical interval can be any quantitative value, such as a number, a percentage, a ratio, etc. The "numerical interval" allows a broad definition of the quantitative interval, such as the percentage interval, the ratio interval, the value interval, etc.

[0053] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used in the description herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items.

[0054] The embodiments of the present application provide a double-stage non-contact membrane distillation wastewater treatment device to solve at least one of the following technical problems in the prior art: (1) when a filtration method, an ion exchange method, an evaporation concentration method, an adsorption method, a biological treatment method or a combination of these processes is used, there are problems of complex system setting, high energy consumption, large amount of solid waste generated, high investment, operation and maintenance costs; (2) when a membrane distillation technology is used to treat radioactive wastewater, there are problems of short service life of the membrane, low and unstable flux, easy damage of the membrane and difficulty in online detection; (3) the membrane distillation technology needs to maintain a large temperature difference between the two sides of the membrane, which has the problem of high energy consumption; (4) for wastewater generated in a hospital nuclear medicine department and the like which is difficult to purify, single membrane distillation purification treatment often cannot meet the actual needs. The double-stage non-contact membrane distillation wastewater treatment device will be described below with reference to the accompanying drawings.

[0055] The two-stage non-contact membrane distillation wastewater treatment device 10 provided in this application embodiment is exemplary; please refer to [link to example]. Figure 1 As shown, Figure 1 This is a schematic diagram of the structure of the two-stage non-contact membrane distillation wastewater treatment device 10 provided in an embodiment of this application. The two-stage non-contact membrane distillation wastewater treatment device 10 of this application can be used for radioactive wastewater treatment, meeting the needs of nuclear medicine departments, nuclear power plants, spent fuel processing plants, and other facilities for radioactive wastewater treatment.

[0056] To more clearly illustrate the structure of the two-stage non-contact membrane distillation wastewater treatment device 10, the following description of the two-stage non-contact membrane distillation wastewater treatment device 10 will be provided in conjunction with the accompanying drawings.

[0057] For example, please refer to Figure 1 As shown, a two-stage non-contact membrane distillation wastewater treatment device 10 includes an evaporation tower 100, a first membrane distillation assembly 210, a second membrane distillation assembly 220, a first blower 310, a second blower 320, an evaporation heat exchange assembly 400, a temperature and humidity control assembly 500, a cyclone separator 600, and a heating assembly 700. The evaporation tower 100, first membrane distillation assembly 210, first blower 310, second membrane distillation assembly 220, second blower 320, evaporation heat exchange assembly 400, temperature and humidity control assembly 500, and cyclone separator 600 are connected sequentially. The cyclone separator 600 is also connected to the evaporation tower 100 via the second membrane distillation assembly 220 and the first membrane distillation assembly 210. The first membrane distillation assembly 210 is disposed inside the evaporation tower 100 and near the top of the evaporation tower 100. The heating assembly 700 is connected to the evaporation tower 100 for heating and treating the radioactive wastewater within the evaporation tower 100. The first fan 310 assists in the diffusion of high-humidity gas from the evaporation tower 100 through the first membrane distillation module 210. The second fan 320 assists in the diffusion of high-humidity gas from the first membrane distillation module 210 through the second membrane distillation module 220. The evaporation heat exchange module 400 exchanges heat with the high-temperature water vapor from the second fan 320. The temperature and humidity control module 500 cools the low-temperature water vapor from the evaporation heat exchange module 400 after heat exchange. The cyclone separator 600 separates the low-temperature water vapor from the temperature and humidity control module 500 to produce a secondary purified liquid. The dry, cold air separated by the cyclone separator 600 is circulated between the second membrane distillation module 220 and the first membrane distillation module 210.

[0058] In some embodiments, the first membrane distillation assembly 210 is disposed inside the evaporation tower 100. The second membrane distillation assembly 220 is disposed outside the evaporation tower 100. This application uses a two-stage membrane distillation system consisting of the first membrane distillation assembly 210 and the second membrane distillation assembly 220 to treat radioactive wastewater, which can improve water treatment efficiency and effectiveness.

[0059] In some embodiments, the dual-stage non-contact membrane distillation wastewater treatment device 10 further comprises a flow sensor 800. The flow sensor 800 is disposed on the circulation pipe 101 between the second membrane distillation assembly 220 and the second air blower 320 for detecting the flow rate of the high-temperature water vapor in the circulation pipe 101.

[0060] In some embodiments, the heating assembly 700 can be an electromagnetic heater. An electromagnetic heater is a device that generates heat using the principle of electromagnetic induction. The working principle of an electromagnetic heater is as follows: electromagnetic heating is based on Faraday's law of electromagnetic induction. When an alternating current passes through a coil, a changing magnetic field is generated around the coil. If a conductive material (usually metal) is placed in this magnetic field, eddy currents will be generated inside the material. These eddy currents flow within the conductor and encounter resistance, thereby generating heat. The advantages of electromagnetic heaters include: high energy efficiency: high energy conversion efficiency, most of the input energy can be converted into heat energy; fast heating: can quickly reach the required temperature; clean and environmentally friendly: no combustion process, no waste gas or harmful substances; high safety: the surface does not directly heat, reducing the risk of burns; easy to control: can accurately control the heating speed and temperature by adjusting the current size.

[0061] In some embodiments, the temperature and humidity adjusting assembly 500 can be a surface cooler. A surface cooler is usually composed of a series of heat exchange pipes and fins. The heat exchange pipes are internally circulated by hot steam. When external air passes through these fins, the air exchanges heat with the hot steam inside the heat exchange pipes, thereby cooling the hot steam inside the pipes. At the same time, the hot steam is cooled by the surface cooler, and part of the water vapor condenses into water droplets, thereby reducing the humidity and temperature in the pipes. The structure of the surface cooler includes: heat exchange pipes: for passing high-temperature gas; fins: increase the heat exchange area and improve the heat exchange efficiency; frame: supports the entire structure and facilitates installation in air conditioning systems. The main functions of the surface cooler include: cooling: the temperature of the medium inside the pipes is lowered through heat exchange; dehumidification: in the process of exchanging with external air, the moisture inside the pipes condenses into water droplets, thereby removing the humidity in the pipes.

[0062] In some embodiments, the dual-stage non-contact membrane distillation wastewater treatment device 10 further comprises a first temperature and humidity sensor 910. The first temperature and humidity sensor 910 is disposed on the circulation pipe 101 between the second membrane distillation assembly 220 and the second air blower 320 for detecting the temperature and humidity of the high-temperature water vapor in the circulation pipe 101.

[0063] In some embodiments, the double-stage non-contact membrane distillation wastewater treatment device 10 further comprises a second temperature and humidity sensor 920, which is arranged on the circulating pipeline 101 between the second membrane distillation assembly 220 and the second fan 320 to detect the temperature and humidity of the high-temperature water vapor in the circulating pipeline 101.

[0064] In some embodiments, the double-stage non-contact membrane distillation wastewater treatment device 10 further comprises a gas supplement pipeline 104 and a gas supplement valve 1000. The gas supplement pipeline 104 is connected to the circulating pipeline 101 between the second membrane distillation assembly 220 and the second fan 320, and the gas supplement valve 1000 is installed on the gas supplement pipeline 104 to supplement gas into the circulating pipeline 101 between the second membrane distillation assembly 220 and the second fan 320. The first fan 310 and the second fan 320 can also realize the circulation speed of the gas in the circulating pipeline 101 and have a blowing effect on the hydrophobic membrane surface of the membrane distillation assembly 200.

[0065] In some embodiments, the double-stage non-contact membrane distillation wastewater treatment device 10 further comprises a pressure sensor 1100. The pressure sensor 1100 is arranged on the circulating pipeline 101 between the cyclone water separator 600 and the first membrane distillation assembly 210 to detect the pressure of the dry and cold air in the circulating pipeline 101.

[0066] In some embodiments, the double-stage non-contact membrane distillation wastewater treatment device 10 further comprises a third temperature and humidity sensor 1200. The third temperature and humidity sensor 1200 is arranged on the circulating pipeline 101 between the cyclone water separator 600 and the second membrane distillation assembly 220 to detect the temperature and humidity of the dry and cold air in the circulating pipeline 101.

[0067] The double-stage non-contact membrane distillation wastewater treatment device 10 described above is provided with various sensors such as the flow sensor 800, the first temperature and humidity sensor 910, the second temperature and humidity sensor 920, the pressure sensor 1100, and the third temperature and humidity sensor 1200, which can monitor the running stability of the device in real time and ensure the reliability of the device during long-term operation.

[0068] In some embodiments, the double-stage non-contact membrane distillation wastewater treatment device 10 further comprises a first-stage purified liquid outlet pipeline and a first-stage purified liquid outlet valve 1310. The first-stage purified liquid outlet pipeline is connected to the second membrane distillation assembly 220 to discharge the first-stage purified liquid separated by the second membrane distillation assembly 220, and the first-stage purified liquid outlet valve 1310 is installed on the first-stage purified liquid outlet pipeline.

[0069] In this application, the first-stage purified liquid outlet pipeline and the first-stage purified liquid outlet valve 1310 are arranged below the second membrane distillation assembly 220 and can be used for sampling and detecting the first-stage purified liquid to adjust the treatment process in real time.

[0070] In some embodiments, the double-stage non-contact membrane distillation wastewater treatment device 10 further comprises a secondary purified liquid outlet pipe and a secondary purified liquid outlet valve 1320. The secondary purified liquid outlet pipe is connected to the cyclone water distributor 600 for discharging the secondary purified liquid separated by the cyclone water distributor 600. The secondary purified liquid outlet valve 1320 is installed on the secondary purified liquid outlet pipe. When the secondary purified liquid accumulates to a certain amount, the secondary purified liquid outlet valve 1320 is opened to discharge.

[0071] In some embodiments, the double-stage non-contact membrane distillation wastewater treatment device 10 further comprises a compressor 1400, a shell-and-tube heat exchanger 1500, and a wastewater circulating pump 1600. The evaporation tower 100, the heating assembly 700, and the shell-and-tube heat exchanger 1500 are connected in circulation through the heating pipe 103. The wastewater circulating pump 1600 is installed on the heating pipe 103. The shell-and-tube heat exchanger 1500, the evaporation heat exchange assembly 400, and the compressor 1400 can constitute a high-temperature heat pump system. The wastewater circulating pump 1600 is used to realize heat exchange of the radioactive wastewater in the evaporation tower 100 through the shell-and-tube heat exchanger 1500 and heating through the heating assembly 700. The shell-and-tube heat exchanger 1500 is also connected in circulation with the evaporation heat exchange assembly 400 through the heat pump system pipe 102. The compressor 1400 is installed on the heat pump system pipe 102. The heat pump system pipe 102 is provided with a refrigerant. The refrigerant passes through the evaporation heat exchange assembly 400 to exchange heat with the high-temperature water vapor in the evaporation heat exchange assembly 400 to absorb the heat of the high-temperature water vapor. The compressor 1400 is used to realize that the refrigerant in the heat pump system pipe 102 changes from normal temperature and pressure to high temperature and high pressure and then is input into the shell-and-tube heat exchanger 1500 to exchange heat with the radioactive wastewater in the shell-and-tube heat exchanger 1500 to improve the heating efficiency. The double-stage non-contact membrane distillation wastewater treatment device 10 of the present application realizes the heat recovery function of the high-temperature water vapor through the heat exchange loop composed of the shell-and-tube heat exchanger 1500, the evaporation heat exchange assembly 400, and the compressor 1400, and the recovered heat is used for heating the radioactive wastewater, further reducing the energy consumption requirement.

[0072] It should be noted that, in the actual treatment process, the heating assembly 700 can be started first, and after the temperature of the radioactive wastewater is raised to a preset temperature, the high-temperature heat pump system is started. The shell-and-tube heat exchanger 1500 is started to use the heat exchange function of the shell-and-tube heat exchanger 1500 to use the heat exchange heat of the evaporation heat exchange assembly 400 to perform main heating on the radioactive wastewater. The high-temperature heat pump system has a higher COP (COP is greater than 3.5) to reduce energy consumption.

[0073] In some embodiments, the double-stage non-contact membrane distillation wastewater treatment device 10 further comprises a spiral nozzle 1700. The spiral nozzle 1700 is installed in the evaporation tower 100 and is close to the lower part of the first membrane distillation assembly 210. The spraying direction of the spiral nozzle 1700 is downward to the bottom of the evaporation tower 100, and the spiral nozzle 1700 is connected to the heating pipe 103 extending into the evaporation tower 100. The refrigerant in the heat exchange pipe is changed from normal temperature and pressure to high temperature and pressure state by the mechanical movement of the compressor 1400, and then the heat exchange between the shell and tube heat exchanger 1500 and the radioactive wastewater in the shell and tube heat exchanger 1500 is carried out to improve the heating efficiency of the radioactive wastewater. At this time, the radioactive wastewater in the heating pipe 103 is sprayed out from the spiral nozzle 1700 in the form of high-temperature gas-liquid mixture, and the spraying direction downward ensures that the radioactive wastewater does not directly contact the first membrane distillation assembly 210. In addition, since the first membrane distillation assembly 210 is close to the top of the evaporation tower 100, the water level of the radioactive wastewater to be treated in the evaporation tower 100 is lower than the first membrane distillation assembly 210, so that the non-contact membrane distillation wastewater treatment form is realized.

[0074] In some embodiments, the double-stage non-contact membrane distillation wastewater treatment device 10 further comprises a water supplement pump 1800. The water supplement pump 1800 is installed on the liquid inlet pipe 105 of the evaporation tower 100 for pumping the radioactive wastewater to be treated.

[0075] In some embodiments, the first membrane distillation assembly 210 comprises a hydrophobic membrane. The first membrane distillation assembly 210 is divided into three parts: a hot side, a hydrophobic membrane and a cold side. The first membrane distillation assembly 210 is internally provided with a suction pipe, which is located in the cold side for sucking high-temperature water vapor passing through the hydrophobic membrane. The high-temperature and high-pressure gas evaporated in the evaporation tower 100 diffuses to the hot side and is blocked by the hydrophobic membrane. The water molecules pass through the hydrophobic membrane into the cold side to complete the purification by the pressure difference of the water molecules on both sides. The purified high-temperature water vapor is then transported to the second membrane distillation assembly 220 by the first fan 310.

[0076] In some embodiments, the second membrane distillation assembly 220 comprises a hydrophobic membrane. The second membrane distillation assembly 220 is divided into three parts: a hot side, a hydrophobic membrane and a cold side. The second membrane distillation assembly 220 is internally provided with a suction pipe, which is located in the cold side for sucking high-temperature water vapor passing through the hydrophobic membrane. The high-temperature and high-pressure gas from the first membrane distillation assembly 210 diffuses to the hot side and is blocked by the hydrophobic membrane. The water molecules pass through the hydrophobic membrane into the cold side to complete the purification by the pressure difference of the water molecules on both sides. The purified high-temperature water vapor is then transported to the next link by the second fan 320.

[0077] The above-mentioned suction pipe in the first membrane distillation assembly 210 and the second membrane distillation assembly 220 only allows the high-temperature water vapor purified through the hydrophobic membrane to enter, and other impurity components are intercepted.

[0078] In some embodiments, the first membrane distillation assembly 210 can be replaced with a hydrophobic membrane of different pore size and material according to actual use. The second membrane distillation assembly 220 can be replaced with a hydrophobic membrane of different pore size and material according to actual use.

[0079] In some embodiments, the double-stage non-contact membrane distillation wastewater treatment device 10 further comprises a wastewater temporary storage tank. The wastewater temporary storage tank is connected to the evaporation tower 100 through the liquid inlet pipeline 105. The wastewater temporary storage tank can store radioactive wastewater to be treated, and when the radioactive wastewater is stored to a certain amount, the membrane distillation wastewater treatment can be performed. The radioactive wastewater that can be stored in the wastewater temporary storage tank includes radioactive isotope wastewater containing Cs, Sr, mTr, Co, etc. generated by nuclear power plant operation, nuclear facility production, and hospital nuclear medicine department radiotherapy. 133 Cs, 131 I, 89 Sr, 99 mTr, 60 Co, etc.

[0080] The double-stage non-contact membrane distillation wastewater treatment device 10 further comprises a blowdown valve 1900. The blowdown valve 1900 is installed at the blowdown port of the bottom of the evaporation tower 100. The double-stage non-contact membrane distillation wastewater treatment device 10 described above discharges the concentrated wastewater in the evaporation tower 100 regularly by arranging the blowdown valve 1900, so that the radioactive concentration of the wastewater in the evaporation tower 100 is at a reasonable level, thereby ensuring the effect of the wastewater purification treatment during operation. The concentration of the radioactive wastewater in the evaporation tower 100 gradually increases as evaporation proceeds, so that the radioactive wastewater with high concentration is discharged regularly to ensure the controllability of the concentration of the radioactive wastewater in the evaporation tower 100. The discharged radioactive wastewater can be transported back to the wastewater temporary storage tank or transported to other treatment systems.

[0081] An embodiment of the present application provides a double-stage non-contact membrane distillation wastewater treatment method.

[0082] In this document, unless otherwise stated, each reaction step can be carried out in the order described herein or can not be carried out in the order described herein. For example, each reaction step can include other steps therebetween, and the order of the reaction steps can also be appropriately changed. This can be determined by a person skilled in the art according to conventional knowledge and experience. Preferably, the reaction method herein is carried out in sequence.

[0083] A double-stage non-contact membrane distillation wastewater treatment method uses the double-stage non-contact membrane distillation wastewater treatment device 10 described above, and comprises the following steps:

[0084] S1, inputting the radioactive wastewater into the evaporation tower 100 to a preset height.

[0085] S2, control the heating assembly 700 to heat the radioactive wastewater of the evaporation tower 100 to the average water temperature of the radioactive wastewater reaches the preset temperature.

[0086] S3, the radioactive wastewater in the evaporation tower 100 diffuses to the hot side of the first membrane distillation assembly 210 in the form of high humidity gas higher than the preset temperature through evaporation operation, the water molecules in the high humidity gas enter the cold side through the hydrophobic membrane in the first membrane distillation assembly 210 under the action of water molecule pressure, forming high temperature water vapor lower than the preset temperature 10~20℃, which is transported to the second membrane distillation assembly 220 by the circulating pipeline 101 through the first fan 310 for secondary membrane distillation purification.

[0087] S4, the water molecules in the high humidity gas enter the cold side through the hydrophobic membrane in the second membrane distillation assembly 220 under the action of water molecule pressure, and the high temperature water vapor formed is transported to the evaporation heat exchange assembly 400 by the circulating pipeline 101 through the second fan 320 for heat exchange to form low temperature water vapor, and the first stage purification liquid generated by the second membrane distillation assembly 220 is discharged.

[0088] S5, control the temperature and humidity adjusting assembly 500 to cool the low temperature water vapor after heat exchange in the evaporation heat exchange assembly 400, control the cyclone water separator 600 to separate the low temperature water vapor from the temperature and humidity adjusting assembly 500 to produce secondary purification liquid, and the dry cold air separated by the cyclone water separator 600 is input into the evaporation tower 100 through the second membrane distillation assembly 220 and the first membrane distillation assembly 210 for circulation.

[0089] In some embodiments, the radioactive wastewater is input into the evaporation tower 100 to a preset height of 40%~80% of the tower height of the evaporation tower 100 in step S1. Preferably, the radioactive wastewater is input into the evaporation tower 100 to a preset height of 60%~70% of the tower height of the evaporation tower 100.

[0090] In some embodiments, the preset temperature in step S2 can be 100~120℃.

[0091] In some embodiments, the double-stage non-contact membrane distillation wastewater treatment method further comprises the following steps: controlling the circulation of refrigerant in the heat pump system pipeline 102 to realize heat exchange between the refrigerant and the high temperature water vapor in the evaporation heat exchange assembly 400 to form low temperature water vapor from the high temperature water vapor, realize heat recovery, improve the COP of the high temperature heat pump system and reduce energy consumption.

[0092] In some embodiments, the double-stage non-contact membrane distillation wastewater treatment method further comprises the following steps: controlling the compressor 1400 to transport the refrigerant in the heat pump system pipeline 102 from normal temperature and pressure to high temperature and pressure state through mechanical movement, and then to the shell-and-tube heat exchanger 1500 and exchange heat with the radioactive wastewater in the shell-and-tube heat exchanger 1500 to improve the heating efficiency of the radioactive wastewater and the COP of the high-temperature heat pump system, thereby reducing energy consumption. Through the heating assembly 700 and the shell-and-tube heat exchanger 1500, double heating of the radioactive wastewater in the evaporation tower 100 can be realized, and the liquid in the evaporation tower 100 is heated to evaporate, and then the high-temperature and high-pressure gas flows to the hot side of the first membrane distillation assembly 210 through the pressure difference, and is distilled through the first membrane distillation assembly 210.

[0093] The radioactive nuclides in the radioactive wastewater that can be treated by the double-stage non-contact membrane distillation wastewater treatment method include but are not limited to 133 Cs, 131 I, 89 Sr, 99 mTr, 60 Co; the concentration of the radioactive nuclides in the radioactive wastewater is not less than 5x10 6 Bq / L.

[0094] After the radioactive wastewater is treated by the double-stage non-contact membrane distillation wastewater treatment method, the concentration of the radioactive nuclides in the primary purified liquid can be reduced to 25Bq / L~300Bq / L; and the concentration of the radioactive nuclides in the secondary purified liquid can be reduced to 20Bq / L~25Bq / L.

[0095] Embodiment 1

[0096] The embodiment provides a double-stage non-contact membrane distillation wastewater treatment method for treating radioactive wastewater. The radioactive nuclides in the radioactive wastewater include 131 I, and the concentration of the radioactive nuclides in the radioactive wastewater is 5x10 6 Bq / L.

[0097] The embodiment provides a double-stage non-contact membrane distillation wastewater treatment method, which adopts the double-stage non-contact membrane distillation wastewater treatment device 10 described above, and comprises the following steps:

[0098] S1, inputting the radioactive wastewater into the evaporation tower 100 to a height of half of the evaporation tower 100, and the water level at the preset height in the evaporation tower 100 is lower than the first membrane distillation assembly 210.

[0099] S2, controlling the heating assembly 700 to heat and treat the radioactive wastewater in the evaporation tower 100 until the average water temperature of the radioactive wastewater reaches the preset temperature 100℃.

[0100] S3, control the compressor 1400 by mechanical movement to make the refrigerant in the heat pump system pipeline 102 from normal temperature and normal pressure to high temperature and high pressure (105℃, 15bar) state after delivery to the shell and tube heat exchanger 1500 and heat exchange with the radioactive wastewater in the shell and tube heat exchanger 1500 to improve the heating efficiency of the radioactive wastewater. Through the heating assembly 700 and the shell and tube heat exchanger 1500, double heating of the radioactive wastewater in the evaporation tower 100 can be realized, until the temperature of the radioactive wastewater reaches the required vaporization temperature of the first membrane distillation assembly 210.

[0101] S4, the radioactive wastewater in the evaporation tower 100 diffuses to the hot side of the first membrane distillation assembly 210 in the form of high humidity gas with 100% humidity after evaporation operation, the water molecules in the high humidity gas enter the cold side through the hydrophobic membrane in the first membrane distillation assembly 210 under the action of pressure, and the high temperature water vapor formed is delivered to the second membrane distillation assembly 220 through the first fan 310. The first purified liquid produced by the first membrane distillation assembly 210 can be opened regularly, such as every 10 minutes, according to the need, and discharged to the wastewater tank. The concentration of radionuclides in the first purified liquid can be reduced to 98.2 Bq / L.

[0102] S5, control the second membrane distillation assembly 220 to perform secondary membrane distillation purification treatment on the 80℃ high temperature water vapor from the first membrane distillation assembly 210. The high temperature water vapor diffuses to the hot side of the second membrane distillation assembly 220, and the water molecules enter the cold side through the hydrophobic membrane in the second membrane distillation assembly 220 under the action of pressure, and the high temperature water vapor formed is delivered to the evaporation heat exchange assembly 400 through the second fan 320.

[0103] S6, the high temperature water vapor purified by secondary membrane distillation is heat exchanged by the evaporation heat exchange assembly 400 to form 45℃ low temperature water vapor and condense, and the refrigerant in the heat pump system pipeline 102 is compressed after heat absorption by heat exchange and enters the compressor 1400, and the refrigerant at normal temperature and normal pressure is compressed to high temperature and high pressure and enters the shell and tube heat exchanger 1500 to heat the radioactive wastewater.

[0104] S7, control the temperature and humidity adjusting assembly 500 to cool the low temperature water vapor after heat exchange by the evaporation heat exchange assembly 400 to 45℃.

[0105] S8, control the cyclone water separator 600 to separate the low temperature water vapor from the temperature and humidity adjusting assembly 500 to produce secondary purified liquid, and the dry cold air separated by the cyclone water separator 600 is input into the first membrane distillation assembly 210 for circulation.

[0106] S9, open the secondary purification liquid outlet valve 1320 every 10 minutes to discharge the secondary purification liquid separated by the cyclone water separator 600, and the radionuclide concentration of the secondary purification liquid can be reduced to 15.4 Bq / L.

[0107] S10, open the blowdown valve 1900 every 7 days to discharge the concentrated waste liquid in the evaporation tower 100, so that the concentration of the radioactive waste water in the evaporation tower 100 is controlled to be 1.0 x 10 5 ~1×10 7 Bq / L.

[0108] After the above treatment, the radioactive waste water is detected. The radionuclide concentration of the secondary purification liquid treated by the double-stage non-contact membrane distillation waste water treatment method in this embodiment can be reduced to 15.4 Bq / L. It can be seen that the double-stage non-contact membrane distillation waste water treatment method of this embodiment can effectively treat the radionuclide in the radioactive waste water. The hydrophobic membranes of the first membrane distillation assembly 210 and the second membrane distillation assembly 220 are detected, and there is no damage or corrosion phenomenon, indicating that the first fan 310 and the second fan 320 in this application increase the gas circulation speed in the circulation pipeline 101, so that the hydrophobic membrane remains clean and is not easily contaminated.

[0109] In summary, in the above double-stage non-contact membrane distillation waste water treatment device 10, the temperature difference between the hot side and the cold side of the first membrane distillation assembly 210 and the second membrane distillation assembly 220 does not need to be too large to achieve a high membrane flux, and the energy consumption required to maintain the temperature difference between the two sides of the first membrane distillation assembly 210 and the second membrane distillation assembly 220 is low. The first fan 310 and the second fan 320 increase the gas circulation speed in the circulation pipeline 101, and the first fan 310 and the second fan 320 cooperate to realize the blowing effect on the surface of the hydrophobic membrane of the first membrane distillation assembly 210 and the second membrane distillation assembly 220, so that the hydrophobic membrane remains clean and is not easily contaminated, eliminating the risk of membrane damage, reducing the problems of membrane hydrophilization and corrosion, and prolonging the service life of the hydrophobic membrane. The overall durability of the equipment is high. The above double-stage non-contact membrane distillation waste water treatment device 10 has high purification capacity for non-volatile nuclides, ions and molecules in waste water, etc. other than H. 3 By setting the first membrane distillation assembly 210 and the second membrane distillation assembly 220 to cooperate with each other and performing secondary membrane distillation purification by the first membrane distillation assembly 210 and the second membrane distillation assembly 220, the application can be used to treat waste water generated in hospital nuclear medicine departments and other difficult to purify waste water. The radionuclides in the radioactive waste water that can be treated by the application include but are not limited to 133 Cs, 131 I, 89 Sr, 99 mTr, 60 Co, and the radionuclide concentration can be reduced to 5 x 106 Bq / L containing 131 I nuclear waste water purification is the purification of radionuclide concentration of less than 20Bq / L ~ 25Bq / L of purified water. The application can be used not only for nuclear power plant operation and maintenance, nuclear accident emergency, spent fuel reprocessing plant production, hospital radiotherapy and other radioactive waste of high volume reduction and deep purification treatment, but also for seawater desalination and ultrapure water production.

[0110] In the above embodiments, the description of each embodiment has its own focus, and the parts not described in detail in a certain embodiment can be referred to the related description of other embodiments.

[0111] Each technical feature of the above-described embodiments can be combined arbitrarily, and in order to make the description simple, each technical feature in the above-described embodiments is not described in all possible combinations, however, as long as the combination of technical features does not exist contradictory, it should be considered as the scope of the present application.

[0112] The above-described embodiments only express several implementation manners of the present application, and the description is more specific and detailed, but it should not be understood as a limitation on the scope of the patent of the present application. It should be pointed out that for ordinary skilled in the art, without departing from the concept of the present application, a number of modifications and improvements can be made, which all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application should be subject to the appended claims.

Claims

1. A two-stage non-contact membrane distillation wastewater treatment apparatus, characterized by, The double-stage non-contact membrane distillation wastewater treatment device further satisfies at least one of the following conditions:

2. The two-stage non-contact membrane distillation wastewater treatment device according to claim 1, characterized in that, (1) The double-stage non-contact membrane distillation wastewater treatment device further comprises a flow sensor, which is arranged on a circulating pipeline between the second membrane distillation assembly and the second fan to detect the flow of high-temperature water vapor in the circulating pipeline; (2) The double-stage non-contact membrane distillation wastewater treatment device further comprises a first temperature and humidity sensor, which is arranged on a circulating pipeline between the second membrane distillation assembly and the second fan to detect the temperature and humidity of high-temperature water vapor in the circulating pipeline; (3) The double-stage non-contact membrane distillation wastewater treatment device further comprises a second temperature and humidity sensor, which is arranged on a circulating pipeline between the second membrane distillation assembly and the second fan to detect the temperature and humidity of high-temperature water vapor in the circulating pipeline. The double-stage non-contact membrane distillation wastewater treatment device further comprises a gas supplement pipeline and a gas supplement valve, the gas supplement pipeline is connected to the circulating pipeline between the second membrane distillation assembly and the second fan, and the gas supplement valve is installed on the gas supplement pipeline to supplement gas into the circulating pipeline between the evaporation tower and the second fan.

3. The two-stage non-contact membrane distillation wastewater treatment device according to claim 1, characterized in that, The double-stage non-contact membrane distillation wastewater treatment device further satisfies at least one of the following conditions:

4. The two-stage non-contact membrane distillation wastewater treatment device according to any one of claims 1 to 3, characterized in that, ​ (1) the double-stage non-contact membrane distillation wastewater treatment device further comprises a pressure sensor arranged on a circulating pipeline between the cyclone water separator and the second membrane distillation assembly for detecting the pressure of dry cold air in the circulating pipeline; (2) the double-stage non-contact membrane distillation wastewater treatment device further comprises a third temperature and humidity sensor arranged on a circulating pipeline between the cyclone water separator and the second membrane distillation assembly for detecting the temperature and humidity of dry cold air in the circulating pipeline.

5. The two-stage non-contact membrane distillation wastewater treatment device according to any one of claims 1 to 3, characterized in that, The double-stage non-contact membrane distillation wastewater treatment device further satisfies at least one of the following conditions: (1) the double-stage non-contact membrane distillation wastewater treatment device further comprises a first purified liquid outlet pipe and a first purified liquid outlet valve, the first purified liquid outlet pipe is connected to the second membrane distillation assembly for discharging the first purified liquid separated by the second membrane distillation assembly, and the first purified liquid outlet valve is installed on the first purified liquid outlet pipe; (2) the double-stage non-contact membrane distillation wastewater treatment device further comprises a second purified liquid outlet pipe and a second purified liquid outlet valve, the second purified liquid outlet pipe is connected to the cyclone water separator for discharging the second purified liquid separated by the cyclone water separator, and the second purified liquid outlet valve is installed on the second purified liquid outlet pipe.

6. The two-stage non-contact membrane distillation wastewater treatment device according to any one of claims 1 to 3, characterized in that, The double-stage non-contact membrane distillation wastewater treatment device further comprises a heat pump system, such as a compressor, a shell-and-tube heat exchanger, and a wastewater circulating pump, the evaporation tower, the heating assembly, and the shell-and-tube heat exchanger are connected in circulation through a heating pipeline, the wastewater circulating pump is installed on the heating pipeline, and the wastewater circulating pump is used to realize heat exchange of radioactive wastewater in the evaporation tower through the shell-and-tube heat exchanger and heating through the heating assembly; The shell-and-tube heat exchanger is further connected in circulation with the evaporation heat exchange assembly through a heat pump system pipeline, the compressor is installed on the heat pump system pipeline, a refrigerant is arranged in the heat pump system pipeline, the refrigerant passes through the evaporation heat exchange assembly to realize heat exchange of high-temperature water vapor in the evaporation heat exchange assembly to absorb heat of the high-temperature water vapor, and the compressor is used to realize change of the refrigerant in the heat pump system pipeline from normal temperature and pressure to high temperature and high pressure, and then input the shell-and-tube heat exchanger to realize heat exchange with radioactive wastewater in the shell-and-tube heat exchanger to improve heating efficiency.

7. The two-stage non-contact membrane distillation wastewater treatment device according to any one of claims 1 to 3, characterized in that, The double-stage non-contact membrane distillation wastewater treatment device further satisfies at least one of the following conditions: (1) the double-stage non-contact membrane distillation wastewater treatment device further comprises a makeup water pump installed on a liquid inlet pipeline of the evaporation tower for pumping radioactive wastewater to be treated; (2) the first membrane distillation assembly comprises a hydrophobic membrane; (3) the second membrane distillation assembly comprises a hydrophobic membrane.

8. The two-stage non-contact membrane distillation wastewater treatment device according to any one of claims 1-3, characterized in that, The double-stage non-contact membrane distillation wastewater treatment device further satisfies at least one of the following conditions: (1) the double-stage non-contact membrane distillation wastewater treatment device further comprises a wastewater temporary storage tank connected to the evaporation tower through a liquid inlet pipeline; (2) The double-stage non-contact membrane distillation wastewater treatment device further comprises a blowdown valve installed at a blowdown port at the bottom of the evaporation tower.

9. A two-stage non-contact membrane distillation wastewater treatment method, characterized by, The double-stage non-contact membrane distillation wastewater treatment device according to any one of claims 1-8 comprises the following steps: The radioactive wastewater is input into the evaporation tower to a preset height, and the water level of the radioactive wastewater to be treated in the evaporation tower is controlled to be lower than the first membrane distillation assembly, so that the non-contact membrane distillation wastewater treatment form is realized; The heating assembly is controlled to heat the radioactive wastewater in the evaporation tower to a preset temperature, and the radioactive wastewater in the heating pipeline of the heating assembly is sprayed downward in a high-temperature gas-liquid mixed state from the spiral nozzle, and the spraying direction is downward so that the radioactive wastewater does not directly contact the first membrane distillation assembly; The radioactive wastewater in the evaporation tower is diffused to the hot side of the first membrane distillation assembly in the form of high-humidity gas higher than the preset temperature through evaporation, and the water molecules in the high-humidity gas enter the cold side through the hydrophobic membrane in the first membrane distillation assembly under the action of water molecule pressure to form high-temperature water vapor lower than 10-20℃ of the preset temperature, which is transported to the second membrane distillation assembly through the first fan for secondary membrane distillation purification; The water molecules in the high-humidity gas enter the cold side through the hydrophobic membrane in the second membrane distillation assembly under the action of water molecule pressure, and the high-temperature water vapor formed is transported to the evaporation heat exchange assembly through the second fan for heat exchange to form low-temperature water vapor lower than 45℃ and condense into purified water, and the second membrane distillation assembly generates a first purified liquid; The low-temperature water vapor after heat exchange in the evaporation heat exchange assembly is controlled by the temperature and humidity adjusting assembly, and the low-temperature water vapor from the temperature and humidity adjusting assembly is separated by the cyclone water separator to produce a second purified liquid, and the dry and cold air after separation of the cyclone water separator is input into the evaporation tower through the second membrane distillation assembly and the first membrane distillation assembly for circulation.

10. The two-stage non-contact membrane distillation wastewater treatment method according to claim 9, characterized in that, The double-stage non-contact membrane distillation wastewater treatment method further satisfies at least one of the following conditions: (1) The refrigerant in the heat pump system pipeline is controlled to circulate to realize heat exchange between the refrigerant and the high-temperature water vapor in the evaporation heat exchange assembly to form low-temperature water vapor; (2) The compressor is controlled to change the refrigerant in the heat pump system pipeline from normal temperature and pressure to high temperature and pressure state, and then transport the refrigerant to the shell and tube heat exchanger to exchange heat with the radioactive wastewater in the shell and tube heat exchanger to improve the heating efficiency of the radioactive wastewater and the COP of the high-temperature heat pump to reduce energy consumption; (3) Radionuclides in radioactive wastewater include, but are not limited to 133 Cs, 131 I, 89 Sr, 99 mTr, 60 Co; the concentration of radionuclides in radioactive wastewater is not less than 5 x 10 6 Bq / L; (4) The concentration of radionuclides in the first purified liquid can be reduced to 25-300 Bq / L; (5) The concentration of radionuclides in the second purified liquid can be reduced to 20-25 Bq / L.

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