Low-temperature negative pressure concentrating equipment for radioactive wastewater

Abstract

The utility model discloses a kind of radioactive wastewater low-temperature negative pressure concentration equipment, including evaporation system, heat pump system, vacuum system, drainage system, circulation system and online cleaning system, wherein, evaporation system: by at least two parallelly arranged evaporating tank, each evaporating tank bottom is equipped with heating coil pipe, top is connected with condensing tank import by steam pipeline;Evaporating tank inside middle part is equipped with inverted conical demister, top detachably installs high-precision filter, filter filtration accuracy≤0.1 μm;The geometric dimension of single evaporating tank and condensing tank≤120mm;Heat pump system: including frequency conversion compressor, compressor is connected with the heating coil pipe of evaporating tank bottom by refrigerant exhaust pipe. Thus, the present application provides a kind of low-temperature negative pressure environment under high-efficiency evaporation, energy consumption is low, processing capacity is adjustable, system stability is strong radioactive wastewater concentration equipment, solve the problem such as high energy consumption in traditional process, processing flexibility is poor, drainage is not smooth and maintenance complex.

Description

Technical Field

[0001] This utility model relates to the technical field of radioactive wastewater treatment, and in particular to a low-temperature negative pressure concentration device for radioactive wastewater. Background Technology

[0002] Existing radioactive wastewater treatment technologies generally suffer from the following drawbacks with traditional evaporation and concentration equipment:

[0003] 1. High energy consumption: Atmospheric pressure evaporation requires high-temperature heating, which consumes a lot of energy and is prone to the risk of radioactive material volatilization;

[0004] 2. Insufficient processing flexibility: The fixed processing capacity design cannot adapt to the wastewater treatment needs under different operating conditions;

[0005] 3. Poor system stability: Poor drainage under negative pressure can easily cause equipment operation interruption;

[0006] 4. High maintenance costs: Foam entrainment and scaling during the evaporation process lead to frequent equipment cleaning, affecting continuous operation.

[0007] Therefore, there is an urgent need for a radioactive wastewater concentration device that is low in energy consumption, highly safe, and has flexible adjustable processing capacity. Utility Model Content

[0008] This utility model aims to at least partially solve one of the technical problems in the related art.

[0009] Therefore, this utility model provides a radioactive wastewater concentration device that features high-efficiency evaporation under low-temperature negative pressure, low energy consumption, adjustable processing capacity, and strong system stability, solving problems such as high energy consumption, poor processing flexibility, poor drainage, and complex maintenance in traditional processes.

[0010] To achieve the above objectives, this utility model proposes a low-temperature negative pressure concentration device for radioactive wastewater, comprising an evaporation system, a heat pump system, a vacuum system, a drainage system, a circulation system, and an online cleaning system. The evaporation system consists of at least two parallel evaporator tanks, each equipped with a heating coil at its bottom and connected to the inlet of a condenser tank via a steam pipe at its top. Each evaporator tank has an inverted conical demister in its center and a detachable high-precision filter at its top, with a filtration accuracy ≤0.1μm. The geometric dimensions of a single evaporator tank and condenser tank are ≤120mm. The heat pump system includes a variable frequency compressor, which is connected to the heating coil at the bottom of the evaporator tank via a refrigerant exhaust pipe and to the evaporator via a refrigerant return pipe. The condenser coils inside the condenser tank are connected to form a refrigerant circulation loop; the vacuum system includes a vacuum pump, which is connected to the top of the evaporator tank via a vacuum pipe to maintain the vacuum level inside the evaporator tank; the drainage system includes a distilled water tank, which is connected to the condenser tank outlet via a condensate pipe, and the vacuum pipe is connected to both the evaporator tank and the distilled water tank via a switching valve; a normal pressure drain pump is installed at the bottom of the distilled water tank; the circulation system includes a pneumatic diaphragm pump connected to the bottom of the evaporator tank via a circulation pipe, and a pneumatic ball valve installed on the circulation pipe to pump the concentrate into the evaporator tank to form an internal circulation; the online cleaning system includes a cleaning agent storage tank, a circulation pump, and a cleaning pipe, with the circulation pump connected to the bottom of the evaporator tank via the cleaning pipe.

[0011] This utility model discloses a low-temperature negative pressure concentration device for radioactive wastewater, which provides a radioactive wastewater concentration device with high efficiency evaporation, low energy consumption, adjustable processing capacity, and strong system stability under low-temperature negative pressure environment, solving the problems of high energy consumption, poor processing flexibility, poor drainage, and complex maintenance in traditional processes.

[0012] In addition, the radioactive wastewater low-temperature negative pressure concentration device proposed in the application may also have the following additional technical features:

[0013] Specifically, the frequency adjustment range of the variable frequency compressor is 20-60Hz, and the parallel evaporator is connected to the wastewater input pipeline through an independent liquid inlet valve, which can be started and stopped independently to adapt to the treatment capacity adjustment of 20%-100%.

[0014] Specifically, the high-precision filter is a replaceable filter element structure, installed at the top opening of the evaporator and connected by a flange seal, and its produced water has a uranium content ≤10μg / L.

[0015] Specifically, the switching valve of the drainage system is a pneumatic angle valve. When draining, the connection between the evaporator and the distilled water tank is cut off through the switching valve, the vacuum pump is stopped, the distilled water tank is depressurized to normal pressure first, and then the distilled water is discharged through the drainage pump. After the drainage is completed, the distilled water tank is evacuated to the same vacuum level as the evaporator, and then the connection between the evaporator and the distilled water pump is restored.

[0016] Specifically, the inner wall of the evaporator is equipped with a liquid level sensor, which is electrically connected to the liquid inlet valve and the pneumatic diaphragm pump to control the liquid inlet volume and the start and stop of the circulation.

[0017] Specifically, the heating coil is a spiral stainless steel tube, evenly distributed at the bottom of the evaporator, and the condensing coil is a serpentine tube structure, located in the upper middle part of the condensing tank, corresponding to the steam pipe outlet.

[0018] Specifically, the demister is made of polypropylene, is in the shape of an inverted frustum cone, has a bottom diameter that is 1 / 2 of the inner diameter of the evaporator, and a height that is 1 / 3 of the height of the evaporator. It is fixed to the middle of the inner wall of the evaporator by a bracket.

[0019] Specifically, the cleaning pipeline of the online cleaning system is equipped with a solenoid valve, which can alternately perform cyclic cleaning on each evaporator, with a cleaning cycle of 8-24 hours.

[0020] Specifically, the evaporation temperature of the device during operation is 30-40℃, and the coefficient of performance (COP) of the heat pump system is ≥4.0.

[0021] Specifically, the evaporator, condenser, heating coil, and condensing coil are all made of 316L stainless steel with an inner wall roughness Ra≤0.8μm and surface pickling and passivation treatment to meet the requirements of radiation protection.

[0022] Variable frequency compressor: Utilizing Danfoss technology. The FC103 series industrial variable frequency compressor has a frequency adjustment range of 20-60Hz, is compatible with heat pump systems, supports Modbus communication, has a corrosion-resistant coating, and an IP54 protection rating.

[0023] Vacuum pump: Pfeiffer MVP 250 rotary vane vacuum pump, ultimate vacuum ≤10⁻³ mbar, pumping speed 250 m / s. 3 / h, suitable for maintaining continuous negative pressure in radioactive environments.

[0024] Pneumatic diaphragm pump: Employs Wilden 700 series polypropylene pneumatic diaphragm pump, resistant to acid and alkali corrosion, with a flow range of 5-50 m³ / h. 3 / h, the material conforms to ANSI / ASME standards and is suitable for the transportation of radioactive concentrates.

[0025] Pneumatic ball valve: ASCO Red-Hat 2-way pneumatic ball valve with stainless steel body is selected. The response time is ≤50ms and it is suitable for rapid on / off control of vacuum systems.

[0026] Liquid level sensor: Employs VEGA VEGAPULS 69 ultrasonic liquid level sensor, non-contact measurement, accuracy ±2mm, suitable for monitoring the level of radioactive liquids, explosion-proof rating Ex ia IIC T6 Ga.

[0027] Inlet valve: The Burkert 2000 series electric ball valve is selected. It is made of stainless steel, has an IP67 protection rating, supports PROFINET communication, and is suitable for precise liquid inlet control in vacuum environments.

[0028] Switching valve (pneumatic angle valve): adopts LOCKE valve series pneumatic angle valve, with a response time ≤30ms, valve body material 316L stainless steel, suitable for -0.095MPa vacuum environment, and life ≥1 million cycles.

[0029] Atmospheric pressure drainage pump: Grundfos CR32-10 stainless steel centrifugal pump, flow rate 10m³ / h. 3 With a flow rate of / h, a head of 30m, and a motor power of 2.2kW, it is suitable for leak-free conveying of distilled water under normal pressure.

[0030] PLC controller: adopts Siemens S7-1200 CPU 1214C AC / DC / Rly, supports multi-axis frequency conversion control and liquid level linkage logic, protection level IP20, and built-in PROFINET interface.

[0031] Human-Machine Interface (HMI): Weintek MT8102 iE 10-inch touchscreen is selected, which supports real-time monitoring of parameters such as vacuum, temperature, and liquid level, and integrates fault alarm and filter replacement reminder functions.

[0032] Uranium concentration detector: The Hach online uranium ion detector is used, with a detection range of 0-100μg / L, an accuracy of ±1μg / L, and supports 4-20mA signal output, making it suitable for monitoring radioactive water quality.

[0033] Temperature sensor: Heraeus CTP100 temperature transmitter is selected, with a measurement range of -50 to 200℃ and an accuracy of ±0.5℃. It features a 316L stainless steel probe and is suitable for real-time temperature monitoring inside evaporators.

[0034] High-precision filter element: Uses Pall UHP series ceramic membrane filter element with filtration accuracy of 0.1μm, multi-layer composite structure with ion exchange coating, suitable for radioactive particle interception, and passed IAEA radiation test.

[0035] Heating / Condensing Coil: Adopts Alfa Laval spiral / serpentine stainless steel heat exchange tubes, material 316L, roughness Ra≤0.8μm, pressure ≥3.0MPa, and is ASME BPVC pressure vessel certified, suitable for high-efficiency heat exchange in heat pump systems.

[0036] The advantages of this invention compared to existing technologies are as follows:

[0037] (1) The heat pump system integrates heating and cooling functions, and realizes the evaporation-condensation energy closed loop through the refrigerant phase change, which significantly reduces energy consumption and improves energy utilization efficiency; the multi-unit parallel connection and frequency conversion regulation design can dynamically match the operating power according to the real-time processing needs and flexibly adapt to the needs of different processing scales.

[0038] (2) The low-temperature evaporation process based on the vacuum negative pressure environment effectively suppresses the risk of radioactive material volatilization; the geometric dimensions of the key components of the equipment meet the critical safety design requirements for the treatment of radioactive wastewater containing uranium, thus avoiding nuclear criticality risks from a structural perspective and adapting to the safety specifications of radioactive sites.

[0039] (3) The evaporation system has a built-in multi-stage interception device. Through the synergistic effect of the demister and high-precision filter components, it effectively intercepts radioactive nuclides. The quality of the produced water meets the stringent discharge standards and can be directly reused or discharged in compliance with the standards.

[0040] (4) The independent depressurization-vacuuming process solves the drainage problem in the traditional negative pressure environment, ensuring the continuous and stable operation of the equipment; the integrated online cleaning function can automatically clean the evaporation components periodically, reducing the frequency of manual maintenance and improving the utilization rate of the equipment.

[0041] (5) The modular parallel design supports dynamic adjustment of processing capacity. The unit can be started and stopped flexibly according to parameters such as wastewater flow rate and concentration, taking into account both small-batch emergency treatment and large-scale continuous operation scenarios, significantly improving process adaptability.

[0042] Additional aspects and advantages of this invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0043] The above and / or additional aspects and advantages of this utility model will become apparent and readily understood from the following description of the embodiments taken in conjunction with the accompanying drawings, in which:

[0044] Figure 1 This is a perspective view of a low-temperature negative pressure concentration device for radioactive wastewater according to an embodiment of the present invention.

[0045] Figure 2 This is a perspective view of a low-temperature negative pressure concentration device for radioactive wastewater according to another embodiment of the present invention;

[0046] Figure 3 This is a perspective view of a low-temperature negative pressure concentration device for radioactive wastewater according to another embodiment of the present invention;

[0047] Figure 4 This is a side view of a low-temperature negative pressure concentration device for radioactive wastewater according to an embodiment of the present invention;

[0048] Figure 5 A simplified flowchart illustrating the functional principle of a heat pump system in a low-temperature negative pressure concentration device for radioactive wastewater according to one embodiment of this utility model.

[0049] Figure 6 This is a control connection flowchart of a low-temperature negative pressure concentration device for radioactive wastewater according to one embodiment of the present invention.

[0050] As shown in the figure: 1. Evaporator; 2. Condenser; 3. Variable frequency compressor; 4. Vacuum pump; 5. Inverted cone demister; 6. High-precision filter; 7. Pneumatic diaphragm pump; 8. Pneumatic ball valve; 9. Liquid level sensor; 10. Distilled water tank; 11. Heating coil; 12. Steam pipe; 13. Circulation pipe; 15. Liquid inlet valve; 21. Condensate coil; 22. Condensate pipe; 31. Refrigerant exhaust pipe; 32. Refrigerant return pipe; 41. Vacuum tube; 42. Switching valve; 51. Bracket; 61. Flange; 101. Atmospheric pressure drain pump; 141. Cleaning pipe; 142. Solenoid valve. Detailed Implementation

[0051] The embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention. Rather, the embodiments of the present invention include all variations, modifications, and equivalents falling within the spirit and scope of the appended claims.

[0052] The following description, in conjunction with the accompanying drawings, describes a low-temperature negative pressure concentration device for radioactive wastewater according to an embodiment of the present invention.

[0053] like Figures 1-6 As shown in the figure, a low-temperature negative pressure concentration device for radioactive wastewater according to an embodiment of the present invention may include an evaporation system, a heat pump system, a vacuum system, a drainage system, a circulation system, and an online cleaning system.

[0054] The evaporation system consists of at least two evaporator tanks 1 connected in parallel, with heating coils 11 (spiral stainless steel pipes, evenly distributed, providing evaporation heat) at the bottom, and a condenser tank 2 (receiving steam) connected to the top via a steam pipe 12. Inside the tank, there is an inverted conical demister 5 (made of polypropylene, inverted frustum-shaped, with a base diameter half the tank's inner diameter and a height one-third of the tank's height, intercepting liquid droplets), and a high-precision filter 6 at the top (with replaceable filter cartridges, filtration accuracy ≤0.1μm, trapping radioactive particles). The dimensions of a single tank and the condenser tank 2 are ≤120mm (critical safety design).

[0055] Heat pump system: The variable frequency compressor 3 forms a refrigerant cycle (heat is transferred from the condensing end to the evaporating end, improving energy efficiency) through the refrigerant exhaust pipe 31 (connected to the heating coil 11) and the refrigerant return pipe 32 (connected to the condensing coil 21 in the condensing tank 2, the serpentine pipe, and the condensing vapor).

[0056] Vacuum system: Vacuum pump 4 is connected to the top of evaporator 1 via vacuum tube 41 to maintain the vacuum inside the tank (the negative pressure required for low-temperature evaporation at 30-40℃).

[0057] Drainage system: Distilled water tank 10 is connected to condenser tank 2 via condensate pipe 22, and the connection is disconnected by switching valve 42 on vacuum pipe 41. During drainage: switching valve 42 disconnects evaporator 1 from distilled water tank 10, disconnects vacuum pump 4, and depressurizes distilled water tank 10 to atmospheric pressure;

[0058] Start the atmospheric pressure drainage pump 101 to drain the water;

[0059] After draining, vacuum pump 4 evacuates the distilled water tank 10 (at the same pressure as evaporator 1) and restores the original connection (to avoid negative pressure leakage and ensure continuous operation).

[0060] Circulation system: The bottom of the evaporator 1 is connected to the pneumatic diaphragm pump 7 via the circulation pipe 13. The pneumatic ball valve 8 on the pipe controls the on / off state, pumping the concentrate back into the tank for circulation (improving concentration efficiency and enriching radioactive materials).

[0061] Online cleaning system: includes cleaning agent storage tank, circulation pump, and cleaning pipeline 141 (connected to the bottom of evaporator 1, regularly circulating and cleaning the inner wall to remove scale).

[0062] Workflow:

[0063] 1. Vacuum establishment:

[0064] Vacuum pump 4 starts and evacuates evaporator 1 through vacuum tube 41 (maintaining a negative pressure environment for evaporation at 30-40℃). Wastewater enters the tank through inlet valve 15, and liquid level sensor 9 monitors the liquid level.

[0065] 2. Evaporation-condensation cycle:

[0066] When the variable frequency compressor 3 is running, the refrigerant releases heat in the heating coil 11, causing the wastewater to evaporate. The steam is then defoamed by the demister 5 and filtered by the high-precision filter 6 before entering the condenser tank 2 through the steam pipe 12. In the condenser coil 21, the refrigerant absorbs heat (the steam condenses into distilled water), and the distilled water flows into the distilled water tank 10 through the condensate pipe 22.

[0067] 3. Concentrated internal circulation:

[0068] The concentrated liquid at the bottom of evaporator 1 is circulated back into the tank via pneumatic diaphragm pump 7, circulation pipeline 13, and pneumatic ball valve 8 (to improve enrichment efficiency until the uranium concentration meets the emission standards).

[0069] 4. Negative pressure isolation drainage:

[0070] Depressurization and drainage: Close switching valve 42, (vacuum pump 4 first depressurizes distilled water tank 10 (from negative pressure to normal pressure), start normal pressure drainage pump 101 to discharge distilled water (avoid drainage under negative pressure to prevent steam leakage).

[0071] Restore vacuum: After draining, vacuum pump 4 evacuates distilled water tank 10 (at the same pressure as evaporator 1), switching valve 42 switches back to evaporator 1, and continues operation (ensuring a continuous and uninterrupted negative pressure environment in the system).

[0072] 5. Online cleaning (performed periodically):

[0073] The circulation pump starts, and the cleaning agent enters each evaporator 1 through the cleaning pipe 141 to circulate and clean each heating coil 11 and other components (removing scale, maintaining heat transfer efficiency, cleaning cycle 8-24 hours).

[0074] In one embodiment of this utility model, such as Figures 1-6 As shown, the frequency adjustment range of the variable frequency compressor 3 is 20-60Hz. The parallel evaporator 1 is connected to the wastewater input pipeline through an independent liquid inlet valve 15, and can be started and stopped independently to adapt to the 20%-100% treatment capacity adjustment.

[0075] It is understandable that the variable frequency compressor 3, as the core energy regulation component of the heat pump system, can steplessly adjust its frequency within the range of 20-60Hz. When the processing capacity is low (such as 20% load), the compressor operates at a low frequency of 20-40Hz to reduce the amount of refrigerant circulating and reduce energy consumption; when the processing capacity is high (such as 100% load), the compressor operates at a high frequency of 40-60Hz to increase the refrigerant flow, enhance the heat output of the heating coil 11, and match the evaporation requirements of multiple tanks connected in parallel.

[0076] Each evaporator 1 is connected to the wastewater inlet pipe via an independent inlet valve 15. The inlet valve 15 is an electric ball valve, which can individually control the inlet flow to the corresponding tank.

[0077] Low throughput (20%-50%): Only open 1-2 evaporators 1, and close the remaining inlet valves 15 to avoid energy waste (e.g., a single tank can handle 20% of the flow rate at full load, or two tanks can each handle 25% of the flow rate).

[0078] High throughput (80%-100%): All inlet valves are fully open at 15%, and multiple tanks are operated in parallel (e.g., 4 tanks in parallel, each tank handles 25% of the flow, and the total throughput is 100%).

[0079] Dynamic processing volume adjustment process:

[0080] 1. Load detection and unit configuration:

[0081] The system monitors the wastewater input flow rate in real time using a flow sensor.

[0082] If the flow rate is ≤ 20% of the design flow rate of a single tank:

[0083] Close the inlet valve 15 of the redundant evaporator 1, leaving only one tank in operation.

[0084] The variable frequency compressor 3 operates at a low frequency of 20-30Hz to reduce heating power (e.g., the evaporation rate of wastewater in evaporator 1 is matched with a low flow rate to avoid the concentrate from becoming too concentrated).

[0085] If the flow rate is ≥ 80% of the design flow rate of a single tank:

[0086] Open the inlet valve 15 of all parallel evaporators 1, allowing multiple tanks to be filled with liquid simultaneously.

[0087] Compressor 3 operates at a high frequency of 30-60Hz to ensure that the heating coil 11 of each tank receives sufficient heat (if 4 tanks are connected in parallel, the total heat demand is 4 times that of a single tank, and high-frequency operation improves the refrigerant circulation efficiency).

[0088] 2. Intermediate load adjustment (30%-70%):

[0089] Unit combination adjustment: Select 2-3 evaporators to operate according to the flow rate (e.g., at 30% flow rate, 1 tank at full load + 1 tank at 30% load, or 3 tanks each at 10% load).

[0090] Dynamic frequency matching: The compressor frequency is linearly adjusted with the flow rate within the range of 30-60Hz (e.g., at 50% flow rate, the frequency is set to 30Hz, and the heat output is 50% of the full load of a single tank × the number of units, ensuring that the total heat is matched with the evaporation demand).

[0091] 3. Feedback control and stability:

[0092] Liquid level feedback: Liquid level sensor 9 inside evaporator 1 monitors the liquid level height.

[0093] If the liquid level is lower than the set lower limit (evaporation is too fast, and the actual processing volume is higher than the detection value), the compressor frequency will be automatically reduced (to reduce heating, reduce the evaporation rate, and avoid the uranium concentration in the concentrate from exceeding the standard), or the inlet valve 15 of the backup tank will be temporarily opened to add wastewater.

[0094] If the liquid level is higher than the set upper limit (evaporation is too slow, and the actual processing capacity is lower than the detection value), increase the compressor frequency (increase heating), or close part of the liquid inlet valve 15 to stop the liquid inlet until the liquid level returns to normal.

[0095] In one embodiment of this utility model, such as Figures 1-6 As shown, the high-precision filter 6 is a replaceable filter element structure, installed at the top opening of the evaporator 1, and sealed by flange 61. Its produced water has a uranium content ≤10μg / L.

[0096] It is understood that the high-precision filter 6 adopts a cartridge design, with the cartridge composed of multiple layers of composite filter materials (such as radiation-resistant ceramic membranes or sintered metal membranes). The cartridge is sealed via flange 61 (a metal sealing flange that matches the flange 61 at the top opening of the evaporator 1), ensuring no leakage in the steam path. When the cartridge reaches the end of its service life (e.g., when trapped radioactive particles cause the filtration resistance to rise to a set threshold), it can be quickly disassembled and replaced.

[0097] Replacement procedure: Close the steam outlet of evaporator 1 (i.e. the connecting valve of steam pipe 12 to ensure system safety), loosen the bolts of flange 61, remove the old filter element, install the new filter element, tighten flange 61 again, and restore system operation.

[0098] Installation location:

[0099] The high-precision filter 6 is located at the top opening of the evaporator 1 and is directly connected in series between the steam outlet and the steam pipe 12. After the large droplets are removed by the inverted cone-shaped demister 5 inside the evaporator 1, the steam first passes through the filter element of the high-precision filter 6 to intercept micron-sized radioactive particles (such as uranium particles with a size ≥0.1μm, which are intercepted by the ≤0.1μm micropores of the filter element).

[0100] Filtration workflow and product water quality control:

[0101] 1. Steam filtration process:

[0102] Evaporation stage: The heating coil 11 at the bottom of the evaporator 1 evaporates the wastewater, producing uranium-containing vapor (containing radioactive pollutants such as uranium aerosols and tiny droplets).

[0103] Defoaming and filtration work together:

[0104] Steam first passes through demister 5 (inverted frustum-shaped, made of polypropylene) to intercept large droplets (droplets with a diameter ≥ 1 mm, reducing the load on the filter element), and then passes through the filter element of high-precision filter 6.

[0105] Physical interception: The microporous structure (≤0.1μm) of the filter element directly blocks uranium particles (uranium oxide particles, uranium-containing colloids), ensuring that particles ≥0.1μm in the steam are completely intercepted.

[0106] Chemical purification: The functional coating (material containing ion exchange groups) on the surface of the filter element affects uranium ions (UO2). 2+ Adsorption is carried out to further reduce the uranium content in the produced water (even if submicron-sized uranium ions are present in the steam, they can be retained through chemical action).

[0107] 2. Water quality assurance:

[0108] Online monitoring: Install a uranium concentration detection device (such as a fluorescence spectrometer) at the outlet of the condensate pipeline 22 or the distilled water tank 10 to monitor the uranium content in the produced water in real time.

[0109] When the detected value is ≥8μg / L (close to the threshold of 10μg / L, with safety redundancy set), the system will automatically prompt to replace the filter cartridge (with an alarm via the human-machine interface) to ensure that the produced water always meets the discharge requirement of ≤10μg / L.

[0110] Filter cartridge performance verification: Before installation, each batch of new filter cartridges undergoes a filtration test in the laboratory simulating uranium vapor (concentration ≥100μg / L) to ensure that its filtration accuracy is ≤0.1μm and the uranium content in the produced water is ≤10μg / L.

[0111] In one embodiment of this utility model, such as Figures 1-6 As shown, the switching valve 42 of the drainage system is a pneumatic angle valve. When draining, the connection between the evaporator 1 and the distilled water tank 10 is cut off through the switching valve 42, the vacuum pump 4 is turned off, the distilled water tank 10 is first depressurized to atmospheric pressure, and then the distilled water is discharged through the atmospheric pressure drainage pump 101. After the drainage is completed, the distilled water tank 10 is first evacuated to the same vacuum level as the evaporator 1, and then the connection between the evaporator 1 and the vacuum pump 4 is restored.

[0112] It can be understood that the switching valve 42 connects the distilled water tank 10 and the evaporator 1, and has three ports. The distilled water tank 10 is connected to the vacuum pump 4. When the switching valve 42 is disconnected and the vacuum pump 4 is turned off, the evaporator 1 maintains its existing vacuum state (the evaporator 1 maintains a vacuum), while the inside of the distilled water tank is connected to the atmosphere for pressure relief and drainage.

[0113] Distilled water tank 10 receives distilled water discharged from condenser 2 through condensate pipe 22, and an atmospheric pressure drain pump 101 is installed at the bottom (it only starts when distilled water tank 10 is at atmospheric pressure to avoid the drain pump not working under negative pressure).

[0114] Drainage process:

[0115] Phase 1: System status before drainage

[0116] Switching valve 42 status: normally open, vacuum pump 4 maintains the vacuum level in evaporator 1.

[0117] State of distilled water tank 10: It is connected to condenser tank 2 through condensate pipe 22, and the internal vacuum degree is the same as that of evaporator tank 1. Due to the negative pressure environment, the distilled water cannot be discharged by atmospheric pressure drain pump 101.

[0118] Phase 2: Depressurized distilled water tank 10

[0119] Switching valve 42 operation:

[0120] Close the pneumatic valve, disconnect the connection between the evaporator 1 and the distilled water tank 10, and simultaneously turn off the vacuum pump 4.

[0121] Depressurization process:

[0122] Vacuum pump 4 stops evacuating the distilled water tank 10, and the distilled water tank 10 automatically depressurizes (i.e., the distilled water tank 10 is connected to the atmosphere and gradually enters the air until its internal pressure rises to atmospheric pressure (0.1MPa)).

[0123] At this time, because the evaporator 1 is disconnected from the distilled water tank 10, it is temporarily in a closed vacuum state, and the internal vacuum degree remains unchanged; because the vacuum pump 4 is turned off, the distilled water tank 10 is connected to the atmosphere, and the pressure gradually decreases to atmospheric pressure.

[0124] Phase 3: Atmospheric Pressure Drainage

[0125] Start the atmospheric pressure drainage pump 101:

[0126] When the pressure in the distilled water tank 10 reaches atmospheric pressure, the control system sends a signal to start the atmospheric pressure drain pump 101, which discharges the distilled water through the drain pipe.

[0127] Drainage process control:

[0128] The operating time of the atmospheric pressure drain pump 101 is controlled by the liquid level sensor 9 in the distilled water tank 10 or by a preset time, ensuring that the distilled water is completely discharged.

[0129] Phase 4: Restore the vacuum level of the distilled water tank to 10 degrees.

[0130] Secondary action of switching valve 42:

[0131] After drainage is completed, vacuum pump 4 is restarted to evacuate distilled water tank 10 until its internal vacuum level is restored to the same set value as evaporator 1.

[0132] Vacuum synchronization logic:

[0133] Once the vacuum level of the distilled water tank 10 reaches the target, the switching valve 42 opens, connecting the distilled water tank 10 to the evaporator 1, and the vacuum pump 4 resumes evaporating the evaporator 1, ensuring that the entire system re-enters a stable negative pressure operating state.

[0134] In one embodiment of this utility model, such as Figures 1-6 As shown, the inner wall of the evaporator 1 is equipped with a liquid level sensor 9, which is electrically connected to the liquid inlet valve 15 and the pneumatic diaphragm pump 7 to control the liquid inlet volume and the start and stop of the circulation.

[0135] It is understood that the liquid level sensor 9 is installed on the inner wall of the evaporator 1, usually at 1 / 3 (low position) and 2 / 3 (high position) of the tank height. It adopts a non-contact ultrasonic sensor or a contact hydrostatic sensor to monitor the liquid level in the tank in real time.

[0136] Electrical connection relationship:

[0137] Liquid level sensor 9 → Inlet valve 15: The electric actuator connected to the inlet valve 15 via a control cable is used to trigger the opening / closing of the valve.

[0138] Liquid level sensor 9 → Pneumatic diaphragm pump 7: Connected to the pump start / stop control circuit via a relay module to control the start / stop of the concentrate circulation.

[0139] Liquid level control workflow:

[0140] Phase 1: Initial Liquid Injection Control

[0141] Equipment startup: Vacuum pump 4 starts drawing a vacuum, and the vacuum level in evaporator 1 rises to the set value (-0.09MPa).

[0142] Inlet valve 15 opens: The level sensor 9 detects that the liquid level in the tank is lower than the low threshold (10% of the tank height) and sends a signal to the inlet valve 15. The valve opens and the radioactive wastewater is drawn into the evaporator 1 through the inlet pipe by vacuum suction.

[0143] Liquid inlet stop condition: When the liquid level sensor 9 detects that the liquid level has reached the high threshold (80% of the tank height), it sends a signal to close the liquid inlet valve 15 and stop the liquid inlet.

[0144] Phase 2: Evaporation Concentration and Cycle Start-up / Stop

[0145] Evaporation process: The variable frequency compressor 3 starts, the heating coil 11 heats the wastewater, the water evaporates into steam, and the liquid level gradually decreases.

[0146] Loop start logic:

[0147] When the liquid level drops to the mid-threshold (50% of the tank height), the liquid level sensor 9 sends a signal to the pneumatic diaphragm pump 7, which starts the pump and opens the pneumatic ball valve 8. The concentrate circulates in the tank through the circulation pipe 13 (to improve evaporation efficiency and prevent local enrichment of radioactive materials).

[0148] If the liquid level continues to drop to the low threshold (10% of the tank height), it indicates that evaporation is nearing completion. The liquid level sensor 9 sends a signal to stop the pneumatic diaphragm pump 7, shutting off the circulation loop to prevent the pump from running dry and being damaged.

[0149] Phase 3: Response to Abnormal Operating Conditions

[0150] Liquid level over-limit protection:

[0151] Liquid level is higher than the high threshold (inlet valve 15 is faulty and not closed): Liquid level sensor 9 triggers an audible and visual alarm and automatically shuts off the main valve of the inlet pipeline to prevent wastewater from overflowing.

[0152] If the liquid level is below the low threshold and the circulating pump is running (evaporation rate is abnormally fast): the liquid level sensor 9 immediately stops the pneumatic diaphragm pump 7 and sends a fault signal (refrigerant leakage, heating runaway, etc.) to the control system, prompting manual maintenance.

[0153] Phase 4: Drainage and Standby

[0154] Evaporation complete: When the liquid level sensor 9 detects that the liquid level has dropped to the discharge threshold (5% of the tank height), the system determines that the concentration is complete and opens the discharge ball valve to discharge the concentrate.

[0155] Standby mode: After the liquid is drained, the liquid level sensor 9 detects that the liquid level is zero, and the control system enters standby mode to wait for the next liquid inlet command (the liquid inlet valve 15 remains closed until the liquid level is lower than the low threshold).

[0156] In one embodiment of this utility model, such as Figures 1-6 As shown, the heating coil 11 is a spiral stainless steel tube, evenly distributed at the bottom of the evaporator 1, and the condensing coil 21 is a serpentine tube structure, located in the upper middle part of the condenser 2, corresponding to the outlet of the steam pipe 12.

[0157] It is understood that the heating coil 11 is made of spiral stainless steel (material is 316L stainless steel, which is corrosion resistant and meets the requirements of radioactive environment), and is tightly spiraled around the bottom of the evaporator 1. The distance between the outer diameter of the coil and the inner wall of the evaporator 1 is 5-8mm, which ensures the steam flow space while maximizing the heating area.

[0158] Advantages of spiral shape: Compared with straight tubes, the spiral structure can effectively increase the heat transfer area of ​​heating coil 11, and the spiral path extends the refrigerant flow time, thereby enhancing heat exchange efficiency.

[0159] Uniform distribution characteristics: The coils are evenly distributed in concentric circles with the center of the bottom of the evaporator 1 as the origin, ensuring that the wastewater in the tank is heated evenly and avoiding local overheating that could lead to the volatilization of radioactive materials or scaling.

[0160] Heat exchange process:

[0161] The high-temperature and high-pressure refrigerant gas discharged from the variable frequency compressor 3 enters the heating coil 11 through the refrigerant inlet pipe 31, and releases heat in the spiral pipe (heating process). The heating coil 11 transfers heat to the wastewater in the evaporator 1 through the pipe wall, raising the wastewater temperature to 30-40℃ and causing it to evaporate.

[0162] Refrigerant phase change process: The refrigerant condenses from a gaseous state to a liquid state in the heating coil 11. The released latent heat is used for wastewater evaporation. The liquid refrigerant returns to the compressor 3 through the pipeline, completing the heating cycle.

[0163] The condenser coil 21 has a serpentine structure (multiple U-shaped bends connected in series) and is made of the same 316L stainless steel as the heating coil 11. It is located in the upper middle part of the condenser tank 2, and its inlet position directly corresponds to the outlet of the steam pipe 12 (ensuring that the steam directly impacts the surface of the coil).

[0164] Advantages of serpentine coils: The serpentine structure allows the coil to extend the pipe length within a limited space, increasing the contact area between the steam and the coil; at the same time, the steam flows meanderingly between the serpentine coils, extending the residence time and improving the condensation effect.

[0165] The upper-middle layout logic: Steam flows from top to bottom in the condenser tank 2 (the outlet of steam pipe 12 is located in the upper part of the tank). The coil is located in the upper-middle part so that it can come into contact with high-temperature steam first. The condensate will automatically drip to the bottom of the tank due to gravity, avoiding water accumulation and affecting the condensation efficiency.

[0166] Condensation process:

[0167] The steam generated in evaporator 1 enters condenser 2 through steam pipe 12 and comes into contact with the surface of condenser coil 21. The low-temperature, low-pressure refrigerant liquid discharged from variable frequency compressor 3 enters condenser coil 21 through refrigerant exhaust pipe 32, where it absorbs heat from the steam (refrigeration process) in the serpentine pipe, causing the steam to liquefy into distilled water.

[0168] Refrigerant phase change process: The refrigerant vaporizes from liquid to gas in the condenser coil 21, and the latent heat absorbed is used for vapor condensation. The gaseous refrigerant returns to the compressor 3 to complete the refrigeration cycle.

[0169] Distilled water collection: After condensation, the distilled water drips down the surface of the condenser coil 21 to the bottom of the condenser tank 2, and flows into the distilled water tank 10 through the condensate pipe 22.

[0170] In one embodiment of this utility model, such as Figures 1-6As shown, the demister 5 is made of polypropylene and is in the shape of an inverted frustum. The diameter of the bottom surface is 1 / 2 of the inner diameter of the evaporator 1, and the height is 1 / 3 of the height of the evaporator 1. It is fixed to the middle of the inner wall of the evaporator 1 by the bracket 51.

[0171] It is understandable that the demister 5 is made of polypropylene (PP), which has the characteristics of being resistant to chemical corrosion (resisting acid and alkali components in radioactive wastewater), low temperature resistance (adapting to the 30-40℃ working conditions inside the evaporator 1), and light weight (easy to install and maintain). In addition, the surface of polypropylene is non-polar, making it difficult to adsorb radioactive substances, thus reducing the difficulty of subsequent cleaning.

[0172] Inverted frustum-shaped: A frustum-shaped structure with a smaller top and a larger bottom. The diameter of the bottom surface is 1 / 2 of the inner diameter of evaporator 1, the diameter of the top surface is 1 / 3 of the diameter of the bottom surface, and the height is 1 / 3 of the height of evaporator 1.

[0173] The large bottom diameter (accounting for 1 / 2 of the tank's inner diameter) ensures that the rising steam first passes through the wide truncated cone bottom surface, thus expanding the interception area.

[0174] The reduced top diameter guides steam to gather towards the center of the tank, forming a spiral upward airflow, which prolongs the residence time of steam in the demister and improves droplet separation efficiency.

[0175] The bracket 51 is a stainless steel bracket with a symmetrical triangular structure. One end is welded to the bottom edge of the demister cone, and the other end is fixed to the middle of the inner wall of the evaporator 1 by bolts (about 1 / 3 of the total height of the tank from the bottom). This ensures that the central axis of the demister coincides with the axis of the evaporator 1, and avoids uneven steam flow caused by skewness.

[0176] Defoaming process:

[0177] 1. Steam entrains liquid droplets as they rise:

[0178] The heating coil 11 at the bottom of the evaporator 1 heats the wastewater to generate steam, which then flows upward.

[0179] 2. Droplet inertial collision trapping:

[0180] When steam enters the inverted truncated cone region of demister 5, the flow direction changes from vertical upward to deflected towards the center along the surface of the cone, forming a rotating airflow.

[0181] Due to inertia (due to its large mass), the droplets cannot follow the airflow to make a sharp turn and directly impact the surface of the cone, where they are adsorbed and trapped by the polypropylene material (the droplets gather on the surface of the cone to form a liquid film, which flows back to the bottom of the evaporator 1 along the wall of the cone).

[0182] 3. Steam purification output:

[0183] The concentration of droplets carried by the steam after passing through the demister 5 is significantly reduced, and they continue to rise to the high-precision filter 6 at the top of the evaporator 1, where they are further intercepted by submicron particles (uranium colloids), ensuring that the final produced water contains ≤10μg / L of uranium.

[0184] In one embodiment of this utility model, such as Figures 1-6 As shown, the cleaning pipe 141 of the online cleaning system is equipped with a solenoid valve 142, which can alternately perform cyclic cleaning on each evaporator 1, with a cleaning cycle of 8-24 hours.

[0185] It is understood that the cleaning pipe 141 is made of 316L stainless steel (resistant to corrosion by radioactive cleaning agents). The main pipe connects to the cleaning agent storage tank and the circulation pump, and the branch pipes are connected to the following via solenoid valves 142:

[0186] Bottom of evaporator 1: The cleaning fluid inlet is located 50mm below the heating coil 11, ensuring that the cleaning fluid covers the surface of the coil.

[0187] Each evaporator is equipped with one solenoid valve 142:

[0188] Each solenoid valve has a 142 inlet: connected to the outlet of the circulation pump;

[0189] Solenoid valve 142 outlet: connected to the corresponding evaporator 1 cleaning inlet;

[0190] Circulating cleaning workflow:

[0191] Phase 1: Cleaning Preparation

[0192] System downtime:

[0193] Evaporator 1 that needs cleaning is shut down, and the corresponding inlet and outlet pipes are closed. Vacuum pump 4 maintains negative pressure in the other evaporators 1 and continues to operate.

[0194] Cleaning agent preparation:

[0195] Inject a special cleaning agent (such as a 0.5%-2% citric acid solution) into the cleaning agent storage tank, start the circulation pump, and deliver the cleaning agent to the cleaning pipeline 141.

[0196] Phase 2: Cleaning of Evaporator 1

[0197] Valve switching:

[0198] When the evaporator 1 needs cleaning, the solenoid valve 142 is opened, and the cleaning agent enters the bottom of the evaporator 1 through the cleaning pipe 141, submerging the heating coil 11.

[0199] Circulating cleaning:

[0200] The circulating pump is maintained at 3-5m. 3The cleaning agent circulates within evaporator 1 at a flow rate of / h.

[0201] The upward flow washes away the scale (uranium compound deposits) on the surface of the heating coil 11;

[0202] Part of the cleaning fluid enters the upper part of the tank through the circulation pipe 13 via the pneumatic diaphragm pump 7 to rinse the inner wall and the demister 5.

[0203] Cleaning time: 4-8 hours (50% of the total cleaning cycle), during which the circulation pump is intermittently reversed (the flow direction is switched every 30 minutes to enhance turbulence).

[0204] Phase 3: Cleaning fluid discharge and system reset

[0205] Emission process:

[0206] After cleaning is completed, solenoid valve 142 is switched to the closed state, and the discharge valve at the bottom of evaporator 1 is opened to discharge the cleaning waste liquid into the radioactive waste liquid collection tank.

[0207] Rinse with clean water:

[0208] Pour deionized water into the cleaning agent storage tank and repeat the above cycle 2-3 times to thoroughly remove residual cleaning agent.

[0209] System restart:

[0210] Close all discharge valves, resume evaporation system operation, vacuum pump 4 re-establishes negative pressure, and heating coil 11 and condensing coil 21 resume heat exchange function.

[0211] In one embodiment of this utility model, such as Figures 1-6 As shown, the evaporation temperature of the equipment during operation is 30-40℃, and the coefficient of performance (COP) of the heat pump system is ≥4.0.

[0212] It is understood that the vacuum pump 4 maintains the vacuum level in the evaporator 1 (usually -0.08MPa to -0.095MPa) through the vacuum tube 41. According to the boiling point-pressure characteristics of water, when the pressure drops to about -0.09MPa, the boiling point of water can drop to 30-40℃.

[0213] The higher the vacuum level (the lower the pressure), the lower the boiling point. For example:

[0214] At a pressure of -0.08 MPa, the boiling point is approximately 40°C.

[0215] At a pressure of -0.095 MPa, the boiling point is approximately 30°C.

[0216] The variable frequency compressor 3 precisely controls the wastewater temperature in the evaporator 1 by adjusting the refrigerant flow (which is input to the heating coil 11 via the refrigerant discharge pipe 31).

[0217] The temperature sensor monitors the wastewater temperature in real time. When the temperature is >40℃, the compressor 3 reduces the frequency (e.g., from 60Hz to 50Hz) to reduce heat input.

[0218] When the temperature is <30℃, compressor 3 increases the frequency (e.g., from 20Hz to 40Hz) to increase heat output.

[0219] The coefficient of performance (COP) is the ratio of output heat to input electrical energy. This equipment achieves efficient energy transfer through a heat pump cycle using a variable frequency compressor 3.

[0220] The high-temperature and high-pressure refrigerant gas discharged from the compressor (3) enters the heating coil 11 through the refrigerant inlet pipe 31, releases heat (Q1) to heat the wastewater, and the refrigerant condenses into liquid.

[0221] Refrigeration process: Liquid refrigerant enters condenser coil 21 through refrigerant exhaust pipe 32, absorbs heat from steam (Q2) and evaporates into gas, and the steam condenses into distilled water.

[0222] Energy balance: The compressor 3 inputs electrical energy (W) to drive the refrigerant circulation and outputs heat Q1=Q2+W. Therefore, COP=Q1 / W=(Q2+W) / W=1+Q2 / W.

[0223] Since Q2 (heat absorption from condensation) is much greater than W (electrical energy), the COP of this system is ≥4.0 (e.g., when Q2 = 3W, COP = 4.0), meaning that consuming 1 kWh of electricity can output ≥4 kWh of heat.

[0224] In one embodiment of this utility model, such as Figures 1-6 As shown, the evaporator 1, condenser 2, heating coil 11, and condensing coil 21 are all made of 316L stainless steel with an inner wall roughness Ra≤0.8μm, which meets the requirements for radiation protection.

[0225] It is understandable that the inner walls of all components in contact with radioactive fluids are mechanically or electrolytically polished to achieve Ra≤0.8μm (mirror-grade smooth surface):

[0226] Reduce radioactive adsorption: The micropores on rough surfaces (micron-sized pits that exist when Ra > 0.8 μm) easily trap radioactive colloids or ions, while smooth surfaces make it difficult for radioactive substances to adhere as they flow with the fluid.

[0227] Improved cleaning efficiency: The smooth inner wall allows cleaning agents (such as nitric acid solution) to evenly cover the surface, making it difficult for scale (such as uranium hydroxide) to adhere, and the cleaning cycle can be extended to 8-24 hours.

[0228] It should be noted that the control method of this application can be automatically controlled by a controller. The control method of the controller can be implemented by simple programming by those skilled in the art, which is common knowledge in the field. Furthermore, this application is mainly used to protect mechanical structures, so the control method and circuit connection will not be explained in detail here.

[0229] Specifically, taking the treatment of uranium-containing radioactive wastewater as an example, the complete workflow of the equipment is as follows:

[0230] 1. Equipment startup and vacuum establishment

[0231] Turn on vacuum pump 4 and evacuate evaporator 1 through vacuum tube 41 to maintain the vacuum level inside the tank at -0.09MPa (corresponding to evaporation temperature 35℃).

[0232] The liquid level sensor 9 detects that the liquid level in the evaporator 1 is lower than the low threshold (10% of the tank height), triggering the opening of the inlet valve 15. Radioactive wastewater is then drawn into the tank through the wastewater inlet pipe by vacuum suction.

[0233] When the liquid level reaches the high threshold (80% of the tank height), the liquid level sensor 9 sends a signal to close the inlet valve 15 and stop the liquid inlet.

[0234] 2. Evaporation Concentration and Heat Pump Circulation

[0235] Start the variable frequency compressor 3, and the refrigerant enters the heating coil 11 (a spiral stainless steel tube, evenly distributed at the bottom of the evaporator 1) through the refrigerant inlet pipe 31, releasing heat to heat the wastewater to 35°C for evaporation.

[0236] The steam generated by evaporation carries liquid droplets upwards. First, it passes through an inverted cone-shaped demister 5 (made of polypropylene, with a bottom diameter equal to 1 / 2 of the tank's inner diameter) to intercept large droplets. Then, it passes through a high-precision filter 6 (with a replaceable filter element and a filtration accuracy of ≤0.1μm) to trap micron-sized uranium particles. The purified steam then enters the condenser tank 2 through the steam pipe 12.

[0237] The condenser coil 21 (serpentine structure, arranged in the upper middle part) in the condenser tank 2 receives low-temperature refrigerant through the refrigerant exhaust pipe 32, absorbs steam heat and condenses it into distilled water, and the distilled water flows into the distilled water tank 10 through the condensate pipe 22.

[0238] 3. Concentrate circulation and drainage

[0239] The concentrated liquid at the bottom of the evaporator 1 is pumped into the tank by the pneumatic diaphragm pump 7 through the circulation pipe 13 and the pneumatic ball valve 8 to increase the uranium concentration to ≥200g / L.

[0240] When draining, the switching valve 42 disconnects the evaporator 1 from the distilled water pump 10, the vacuum pump 4 is paused to depressurize the distilled water tank 10 to atmospheric pressure, and the atmospheric pressure drain pump 101 is started to discharge the distilled water.

[0241] After the drainage is completed, vacuum pump 4 first evacuates distilled water tank 10 to the same pressure as evaporator 1, and then restores the connection between evaporator 1 and distilled water tank 10 to maintain continuous negative pressure operation of the system.

[0242] 4. Online cleaning process (24-hour cycle)

[0243] Start the online cleaning system, switch the solenoid valve 142 to the cleaning path of evaporator 1, and the circulating pump pumps 0.5% nitric acid solution into the tank through the cleaning pipe 141 to flush the heating coil 11 and demister 5. After 4 hours, switch to the condenser 2 path to clean the condenser coil 21 (4 hours).

[0244] The cleaning waste liquid is discharged into the radioactive waste liquid tank through the bottom discharge valve, and finally rinsed with deionized water until the pH is neutral to restore the equipment operation.

[0245] In summary, the low-temperature negative pressure concentration equipment for radioactive wastewater according to this utility model provides a radioactive wastewater concentration device with high efficiency evaporation, low energy consumption, adjustable processing capacity, and strong system stability under low-temperature negative pressure environment, solving the problems of high energy consumption, poor processing flexibility, poor drainage, and complex maintenance in traditional processes.

Claims

1. A low-temperature negative pressure concentration device for radioactive wastewater, characterized in that, It includes an evaporation system, a heat pump system, a vacuum system, a drainage system, a circulation system, and an online cleaning system, among which... Evaporation system: Composed of at least two evaporating tanks (1) arranged in parallel, each of the evaporating tanks (1) is provided with a heating coil (11) at the bottom and connected to the inlet of the condensing tank (2) at the top through a steam pipe (12); an inverted cone-shaped demister (5) is provided in the middle of the interior of each evaporating tank (1), and a high-precision filter (6) can be detachably installed at the top, the filter (6) having a filtration accuracy ≤0.1μm; the geometric dimensions of a single evaporating tank (1) and condensing tank (2) are ≤120mm; Heat pump system: includes variable frequency compressor (3), the compressor (3) is connected to the heating coil (11) at the bottom of the evaporator (1) through the refrigerant exhaust pipe (31), and is connected to the condensing coil (21) in the condenser (2) through the refrigerant return pipe (32) to form a refrigerant circulation loop; Vacuum system: including vacuum pump (4), which is connected to the top of evaporator (1) through vacuum tube (41) to maintain the vacuum level inside evaporator (1); Drainage system: includes a distilled water tank (10), which is connected to the outlet of the condenser (2) through a condensate pipe (22), and the vacuum pipe (41) is connected to the evaporator (1) and the distilled water tank (10) respectively through a switching valve (42); the bottom of the distilled water tank (10) is equipped with an atmospheric pressure drain pump (101); Circulation system: The bottom of the evaporator (1) is connected to a pneumatic diaphragm pump (7) through a circulation pipe (13). A pneumatic ball valve (8) is provided on the circulation pipe (13) to pump the concentrate into the evaporator (1) to form an internal circulation. The online cleaning system includes a cleaning agent storage tank, a circulation pump, and a cleaning pipeline (141). The circulation pump is connected to the bottom of the evaporator (1) through the cleaning pipeline (141).

2. The low-temperature negative pressure concentration equipment for radioactive wastewater according to claim 1, characterized in that, The frequency adjustment range of the variable frequency compressor (3) is 20-60Hz. The parallel evaporator (1) is connected to the wastewater input pipeline through an independent liquid inlet valve (15) and can be started and stopped independently to adapt to the 20%-100% processing capacity adjustment.

3. The low-temperature negative pressure concentration equipment for radioactive wastewater according to claim 1, characterized in that, The high-precision filter (6) is a replaceable filter element structure, installed at the top opening of the evaporator (1), and sealed by a flange (61). Its produced water contains uranium ≤10μg / L.

4. The low-temperature negative pressure concentration equipment for radioactive wastewater according to claim 1, characterized in that, The switching valve (42) of the drainage system is a pneumatic angle valve. When draining, the connection between the evaporator (1) and the distilled water tank (10) is cut off through the switching valve (42), the vacuum pump (4) is stopped, the pressure of the distilled water tank (10) is first depressurized to normal pressure, and then the distilled water is discharged through the drain pump (101). After the drainage is completed, the distilled water tank (10) is first evacuated to the same vacuum level as the evaporator (1), and then the connection between the evaporator (1) and the distilled water tank (10) is restored.

5. The low-temperature negative pressure concentration equipment for radioactive wastewater according to claim 1, characterized in that, The evaporator (1) is equipped with a liquid level sensor (9) on its inner wall. The liquid level sensor (9) is electrically connected to the liquid inlet valve (15) and the pneumatic diaphragm pump (7) to control the liquid inlet volume and the start and stop of the circulation.

6. The low-temperature negative pressure concentration equipment for radioactive wastewater according to claim 1, characterized in that, The heating coil (11) is a spiral stainless steel tube, which is evenly distributed at the bottom of the evaporator (1). The condensing coil (21) is a serpentine tube structure, located in the upper middle part of the condensing tank (2), corresponding to the outlet of the steam pipe (12).

7. The low-temperature negative pressure concentration equipment for radioactive wastewater according to claim 1, characterized in that, The demister (5) is made of polypropylene and is in the shape of an inverted truncated cone. The diameter of the bottom surface is 1 / 2 of the inner diameter of the evaporator (1) and the height is 1 / 3 of the height of the evaporator (1). It is fixed to the middle of the inner wall of the evaporator (1) by a bracket (51).

8. The low-temperature negative pressure concentration equipment for radioactive wastewater according to claim 1, characterized in that, The cleaning pipe (141) of the online cleaning system is equipped with a solenoid valve (142), which can alternately clean each evaporator (1) in a cycle of 8-24 hours.

9. The low-temperature negative pressure concentration equipment for radioactive wastewater according to claim 1, characterized in that, The evaporation temperature of the device during operation is 30-40℃, and the coefficient of performance (COP) of the heat pump system is ≥4.

0.

10. A low-temperature negative pressure concentration device for radioactive wastewater according to any one of claims 1-9, characterized in that, The evaporator (1), condenser (2), heating coil (11), and condensing coil (21) are all made of 316L stainless steel with an inner wall roughness Ra≤0.8μm and surface pickling and passivation treatment to meet the requirements of radiation protection.

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