System and method for treating acidic low-level liquid waste

Abstract

The present application relates to waste liquid treatment process technical field, disclose a kind of acid low-leakage waste liquid treatment system and method, acid low-leakage waste liquid treatment system includes: raw water tank, suitable for containing acid low-leakage waste liquid;Heating assembly, suitable for heating waste liquid in raw water tank;Hydrophobic membrane assembly, the raw water outlet of raw water tank is connected with the input end of hydrophobic membrane assembly;Condenser, hot side inlet is connected with the permeation side of hydrophobic membrane assembly;Condensate tank, with the hot side outlet of condenser is connected;Negative pressure mechanism, with the permeation side of hydrophobic membrane assembly is communicated, suitable for the vacuum extraction of the permeation side of hydrophobic membrane assembly.The acid low-leakage waste liquid treatment system of the present application has high purification coefficient, can separate and remove nitric acid and nuclide in waste liquid, so that waste liquid meets discharge requirements and without material liquid boiling can effectively reduce the corrosion and leakage problem of equipment by nitric acid, prolong the service life of equipment, avoid acid waste leakage caused by equipment corrosion, cause pollution to environment or cause harm to human body.

Description

Technical Field

[0001] This invention relates to the field of waste liquid treatment technology, specifically to an acidic low-level radioactive waste liquid treatment system and method. Background Technology

[0002] The acidic low-level radioactive wastewater sources faced by the reprocessing plant have nitric acid concentrations of 0.1–0.4 mol / L and radioactivity concentrations of 1 × 10⁻⁶. 4 Bq / L. Because evaporation is a relatively effective method for removing radionuclides from waste liquids, it is commonly used in reprocessing plants to remove acidic low-level radioactive waste liquids.

[0003] However, when using evaporation to treat acidic low-level radioactive waste, the waste needs to be heated to evaporate. During evaporation, the waste is typically boiling at around 100°C. As the nitric acid in the waste gradually concentrates, the concentrated nitric acid at high boiling temperatures accelerates equipment corrosion, thus limiting the concentration effect and potentially causing leaks, polluting the environment or harming human health. Therefore, there is an urgent need for an acidic low-level radioactive waste treatment system that can effectively treat and concentrate acidic waste without causing equipment corrosion. Summary of the Invention

[0004] In view of this, the present invention provides an acidic low-level radioactive waste liquid treatment system and method to solve the problem that when using evaporation to treat acidic low-level radioactive waste liquid, it is easy to cause equipment corrosion, which restricts the concentration effect of the waste liquid, or even causes waste liquid leakage, polluting the environment or causing harm to the human body.

[0005] In a first aspect, the present invention provides an acidic low-level radioactive waste liquid treatment system, comprising: a feeding tank adapted to contain acidic low-level radioactive waste liquid; a heating device adapted to heat the acidic low-level radioactive waste liquid in the feeding tank; a hydrophobic membrane module, wherein the raw water outlet of the feeding tank is connected to the raw water inlet of the hydrophobic membrane module; a condenser, wherein its hot-side inlet is connected to the permeate side of the hydrophobic membrane module; a condensate tank connected to the hot-side outlet of the condenser; and a negative pressure mechanism connected to the permeate side of the hydrophobic membrane module, adapted to evacuate the permeate side of the hydrophobic membrane module.

[0006] Beneficial effects:

[0007] In the acidic low-level radioactive waste treatment system of this invention, the heating device heats the acidic low-level radioactive waste in the feeding tank to 70-80°C, allowing it to enter the hydrophobic membrane module as steam without boiling. The hydrophobic membrane module can retain nitric acid and radionuclides in the acidic low-level radioactive waste treatment system without causing concentrated nitric acid to accelerate equipment corrosion in a boiling state. The negative pressure mechanism is connected to the permeate side of the hydrophobic membrane module. This configuration increases the membrane flux of the hydrophobic membrane module by increasing the pressure difference across the membrane, thereby increasing the driving force. This promotes the passage of filtered water vapor from the permeate side of the hydrophobic membrane module through the condenser and collection in the condensate tank.

[0008] Furthermore, the acidic low-level radioactive waste treatment system using this scheme has a high purification coefficient for non-volatile nuclides in radioactive waste, and its membrane flux is less affected by salt concentration. Therefore, it can achieve high-fold concentration of radioactive waste and reduce the final volume of radioactive waste.

[0009] Furthermore, under the same nitric acid mass fraction, the partial pressure of nitric acid in an aqueous solution gradually increases with increasing temperature, but is always much lower than the partial pressure of water vapor. Similarly, at the same temperature, the partial pressure of nitric acid in the aqueous solution gradually increases with increasing nitric acid mass fraction, but is always much lower than the partial pressure of water vapor. Therefore, it can be deduced that under the acidic low-level radioactive waste liquid source condition, since the nitric acid concentration is 0.1 mol / L and the mass fraction is less than 20%, its gas partial pressure should be close to 0 at 40–50℃ and less than 0.07 kPa (partial pressure of nitric acid at 20% and 80℃) at 55–80℃. Therefore, the hydrophobic membrane can effectively retain nitric acid.

[0010] Therefore, the acidic low-level radioactive waste liquid treatment system of the present invention can treat acidic low-level radioactive waste liquid, has a good concentration effect, and will not cause equipment corrosion.

[0011] In one alternative implementation, the concentrate outlet of the hydrophobic membrane module is connected to a feed tank.

[0012] Beneficial effects:

[0013] With this setup, the concentrate from the hydrophobic membrane module's outlet can return to the feed tank and be circulated and filtered by the hydrophobic membrane module, thereby improving the treatment capacity of the acidic low-level radioactive wastewater treatment system.

[0014] In one alternative implementation, the hydrophobic membrane assembly includes:

[0015] The outer shell has a raw water inlet and a concentrate outlet.

[0016] Hollow fiber membrane bundles are disposed inside the outer shell, with the first end of the hollow fiber membrane bundle forming the permeation side and the second end being sealed;

[0017] Multiple baffles are spaced apart inside the housing, and hollow fiber membrane bundles pass through the multiple baffles, which are adapted to form a serpentine waterway inside the housing.

[0018] Beneficial effects:

[0019] In this embodiment, during use, acidic low-level radioactive waste liquid enters the shell side of the hydrophobic membrane module through the raw water inlet on the outer casing. The negative pressure mechanism creates negative pressure on the hollow fiber membrane bundle, thereby promoting the water vapor generated by the acidic waste liquid in the shell side of the hydrophobic membrane module to pass through the hollow fiber membrane fibers for filtration and enter the hollow fiber membrane fibers, and then flow out through the permeate side. The baffle increases the flow velocity of the acidic low-level radioactive waste liquid in the shell side, so that the acidic low-level radioactive waste liquid is in a turbulent state in the shell side. The boundary layer thickness between the acidic low-level radioactive waste liquid and the hollow fiber membrane fibers is thinned, improving the efficiency of mass and heat transfer, thereby significantly improving the membrane flux of the hydrophobic membrane module.

[0020] In addition, the hydrophobic membrane module in this embodiment is an external pressure type, which can increase the mass transfer area and the hollow fiber membrane filaments have greater overall strength. Since the acidic low-level radioactive waste liquid in this solution is located in the shell side of the hydrophobic membrane module, the acidic low-level radioactive waste liquid has better fluidity and can reduce the risk of impurities precipitated from the acidic low-level radioactive waste liquid clogging the hollow fiber membrane filaments, thus helping to extend the service life of the hydrophobic membrane module.

[0021] In one alternative embodiment, the heating device includes:

[0022] Solar collectors;

[0023] The inlet of the circulating water tank is connected to the outlet of the solar collector, and the outlet of the circulating water tank is connected to the inlet of the solar collector.

[0024] A fluid drive mechanism, the inlet of which is connected to the outlet of the circulating water tank;

[0025] The heat exchange preheater has its hot-side inlet connected to the outlet of the fluid drive mechanism, its hot-side outlet connected to the circulating water tank, its cold-side inlet suitable for receiving acidic low-level radioactive waste liquid, and its cold-side outlet connected to the feeding tank.

[0026] Beneficial effects:

[0027] The solar collector heats the water in the circulating water tank to above 90°C. The heated liquid enters the circulating water tank and is driven by a fluid drive mechanism to the hot-side inlet of the heat exchange preheater. It then flows back into the circulating water tank through the hot-side outlet and returns to the inlet of the solar collector for reheating. The cold side of the heat exchange preheater receives acidic low-level radioactive waste liquid and exchanges heat between the waste liquid and the hot water in the circulating water tank. The cold-side outlet temperature of the heat exchange preheater is approximately 70°C to 80°C.

[0028] In one alternative embodiment, the heating device includes:

[0029] A semi-circular tube jacketed container, which is fitted on the outside of the feed trough, is suitable for connecting to a steam source.

[0030] Beneficial effects:

[0031] In winter and at night, the solar collector may not be able to heat the liquid in the feed tank to the required temperature. The semi-circular tube jacketed container can use a high-temperature steam source to supplement the heating of the acidic low-electroactive waste liquid in the feed tank.

[0032] In one alternative implementation, the fluid drive mechanism is a circulating water pump, and the outlet of the feed trough is higher than the inlet of the circulating water pump.

[0033] In one alternative embodiment, the heating device includes a steam pipe arranged around the outside of the feed trough, with its inlet end connected to the condensate main of the power plant; or,

[0034] The heating device includes an electromagnetic coil and a frequency converter heating controller. The electromagnetic coil is arranged around the outside of the feeding trough, and the frequency converter heating controller is communicatively connected to the electromagnetic coil.

[0035] In one alternative embodiment, the acidic low-level radioactive waste treatment system further includes a tail gas treatment device connected to the output of the negative pressure mechanism.

[0036] Beneficial effects:

[0037] In addition to the condensed portion, the permeate vapor extracted by the vacuum pump also contains some non-condensable gases. In the condenser, the non-condensable gases mix with the condensate. After being drawn in by the vacuum pump, the gas will carry droplets containing radioactive nuclides. If it is directly discharged into the atmosphere, it will cause radioactive pollution. Therefore, a purification unit is required.

[0038] In one alternative embodiment, the exhaust gas treatment device includes:

[0039] The demister is connected to the output end of the negative pressure mechanism;

[0040] The heater has its inlet connected to the outlet of the demister;

[0041] The filter assembly has its inlet connected to the outlet of the heater.

[0042] Beneficial effects:

[0043] The demister removes radioactive droplets carried in the exhaust gas. Since the filter assembly is made of fiberglass paper, if the exhaust gas has a high moisture content close to the dew point temperature, condensation will occur, wetting the fiberglass paper and causing the high-efficiency filter assembly to fail. Therefore, a heater is needed to increase the temperature difference with the dew point and reduce the moisture content. Ideally, the filter assembly should be able to remove radioactive nuclides carried in the exhaust gas.

[0044] In one alternative implementation, the input end of the negative pressure mechanism is connected to the hot-side outlet of the condenser.

[0045] Beneficial effects:

[0046] With this configuration, the negative pressure mechanism can not only promote water vapor to enter the permeate side of the hydrophobic membrane module through the membrane pores to increase the membrane flux of the hydrophobic membrane module, but also promote the steam on the permeate side of the hydrophobic membrane module to enter the hot side inlet of the condenser, so that the steam passes through the condenser and is condensed into condensate.

[0047] Secondly, the present invention also provides a method for treating acidic low-level radioactive waste liquid, applied to an acidic low-level radioactive waste liquid treatment system, the acidic low-level radioactive waste liquid treatment system comprising:

[0048] The feeding tank is suitable for containing acidic, low-level radioactive waste liquid;

[0049] A heating device suitable for heating acidic low-level radioactive waste liquid in a feeding tank;

[0050] The raw water outlet of the feed tank is connected to the input end of the hydrophobic membrane module.

[0051] The condenser has its hot-side inlet connected to the permeate side of the hydrophobic membrane assembly;

[0052] A condensate tank, which is connected to the hot-side outlet of the condenser;

[0053] A negative pressure mechanism, connected to the permeate side of the hydrophobic membrane module, is suitable for evacuating the permeate side of the hydrophobic membrane module; methods for treating acidic low-level radioactive waste liquid include:

[0054] The heating device is controlled to heat the acidic low-level radioactive waste liquid in the feeding tank to the first preset temperature;

[0055] The heated acidic low-level radioactive waste liquid is transported into the hydrophobic membrane module;

[0056] The negative pressure control mechanism draws negative pressure on the permeation side of the hydrophobic membrane module, so that the permeation side of the hydrophobic membrane module reaches the preset pressure.

[0057] The condenser is controlled to cool the vapor on the permeate side of the hydrophobic membrane module, condensing the vapor into condensate and collecting it in a condensate tank.

[0058] Beneficial effects:

[0059] The acidic low-level radioactive waste liquid treatment method of the second aspect of the present invention uses the acidic waste liquid treatment system of the first aspect of the present invention, and therefore has its beneficial effects, namely: the acidic low-level radioactive waste liquid treatment method of the present invention can treat acidic low-level radioactive waste liquid, has a good concentration effect, and does not cause equipment corrosion.

[0060] In one optional implementation, the first preset temperature is T1, where 70℃≤T1≤80℃; and / or,

[0061] The preset pressure is P, where 6 kPa ≤ P ≤ 15 kPa.

[0062] In one optional embodiment, the acidic low-level radioactive waste treatment system further includes a transfer pump, the input of which is connected to the outlet of the feed tank, and the output of which is connected to the inlet of the hydrophobic membrane module.

[0063] The process of conveying the heated acidic low-level radioactive waste liquid into the hydrophobic membrane module also includes:

[0064] Control the delivery pump to ensure that the flow rate at the input end of the hydrophobic membrane component reaches the preset flow rate.

[0065] In one optional implementation, the preset flow rate is Q, where 400L / h ≤ Q ≤ 600L / h.

[0066] In one optional embodiment, the method for treating acidic low-level radioactive waste further includes:

[0067] Use an alkaline solution to adjust the pH value of the condensate. Attached Figure Description

[0068] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0069] Figure 1 This is a schematic diagram of an acidic low-level radioactive waste liquid treatment system according to an embodiment of the present invention;

[0070] Figure 2 This is a flowchart of an acidic low-level radioactive waste liquid treatment method according to an embodiment of the present invention.

[0071] Explanation of reference numerals in the attached figures:

[0072] 1. Feeding trough;

[0073] 2. Hydrophobic membrane components;

[0074] 4. Condenser;

[0075] 5. Condensate tank;

[0076] 6. Negative pressure mechanism;

[0077] 701. Solar collector; 702. Circulating water tank; 703. Fluid drive mechanism; 704. Heat exchange preheater; 705. Semi-circular tube jacketed container;

[0078] 8. Exhaust gas treatment device; 801. Demister; 802. Heater; 803. Filter set. Detailed Implementation

[0079] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0080] The acidic low-level radioactive wastewater sources faced by the reprocessing plant have nitric acid concentrations of 0.1–0.4 mol / L and radioactivity concentrations of 1 × 10⁻⁶. 4 Bq / L.

[0081] In related technologies, evaporation is generally used to remove radionuclides from acidic low-level radioactive waste liquid. However, during evaporation, the acidic waste liquid is generally boiling at around 100°C. As the nitric acid in the waste liquid gradually concentrates, the concentrated nitric acid will accelerate equipment corrosion under high-temperature boiling conditions, thereby limiting the concentration ratio of the waste liquid.

[0082] Acid separation combined with fine treatment technology is also effective in treating acidic low-level radioactive wastewater. However, this technology has some limitations. As the treatment volume increases, more membrane stacks are required, making the system more complex. Its applicability to different wastewater sources is also limited; currently, the designed influent acidity is between 0.1 and 0.15 mol / L. If the influent acidity is too high, the system cannot be treated. The difficulty in treating acidic low-level radioactive wastewater lies in the fact that most current technologies cannot simultaneously concentrate and separate high concentrations of nitric acid and trace radionuclides without increasing the salt concentration. Commonly used low-level radioactive wastewater treatment technologies such as reverse osmosis, ion exchange, and adsorption all have strict requirements on the pH value of the wastewater. When the acidity is too high, the purification coefficient drops significantly, and the system cannot operate normally.

[0083] The following is combined with Figure 1 The following describes embodiments of the present invention.

[0084] According to an embodiment of the present invention, an acidic low-level radioactive waste liquid treatment system is provided, comprising a feeding tank 1, a heating assembly, a hydrophobic membrane assembly 2, a condenser 4, a condensate tank 5, and a negative pressure mechanism 6. The feeding tank 1 is adapted to contain the acidic low-level radioactive waste liquid. The heating assembly is adapted to heat the acidic low-level radioactive waste liquid in the feeding tank 1. The raw water outlet of the feeding tank 1 is connected to the input end of the hydrophobic membrane assembly 2. The hot-side inlet of the condenser 4 is connected to the permeate side of the hydrophobic membrane assembly 2. The condensate tank 5 is connected to the hot-side outlet of the condenser 4. The negative pressure mechanism 6 is connected to the permeate side of the hydrophobic membrane assembly 2 and is adapted to evacuate the permeate side of the hydrophobic membrane assembly 2.

[0085] During the use of the acidic low-level radioactive waste liquid treatment system of the present invention, the heating component can heat the acidic low-level radioactive waste liquid in the feed tank 1 to 70-80°C, so that it enters the hydrophobic membrane module 2 in the form of steam without boiling. The hydrophobic membrane module 2 can retain nitric acid and radionuclides in the acidic low-level radioactive waste liquid treatment system, and will not cause concentrated nitric acid to accelerate equipment corrosion in a boiling state. The negative pressure mechanism 6 is connected to the permeate side of the hydrophobic membrane module 2. By setting it up in this way, the pressure difference across the membrane can be increased, thereby increasing the driving force and increasing the membrane flux of the hydrophobic membrane module 2. This promotes the water vapor filtered on the permeate side of the hydrophobic membrane module 2 to pass through the condenser 4 and be collected in the condensate tank 5.

[0086] Furthermore, the acidic low-level radioactive waste treatment system using this scheme has a high purification coefficient for non-volatile nuclides in radioactive waste, and its membrane flux is less affected by salt concentration. Therefore, it can achieve high-fold concentration of radioactive waste and reduce the final volume of radioactive waste.

[0087] Furthermore, at the same nitric acid mass fraction, the partial pressure of nitric acid in an aqueous solution gradually increases with increasing temperature, but it is always much lower than the partial pressure of water vapor. Similarly, at the same temperature, the partial pressure of nitric acid in the aqueous solution gradually increases with increasing nitric acid mass fraction, but it is still much lower than the partial pressure of water vapor. Therefore, it can be deduced that under the acidic low-level radioactive waste liquid source condition, since the nitric acid concentration is 0.1 mol / L and the mass fraction is less than 20%, its gas partial pressure should be close to 0 at 40–50℃ and less than 0.07 kPa (partial pressure of 20% nitric acid at 80℃) at 55–80℃. Therefore, the hydrophobic membrane can effectively retain nitric acid.

[0088] Therefore, the acidic low-level radioactive waste liquid treatment system of the present invention can treat acidic low-level radioactive waste liquid, has a good concentration effect, and will not cause equipment corrosion.

[0089] The negative pressure mechanism 6 is preferably, but not limited to, a vacuum pump. The condenser 4 is preferably a shell-and-tube heat exchanger. The heating element can be a heating wire.

[0090] In one embodiment, the concentrate outlet of the hydrophobic membrane module 2 is connected to the feed tank 1. With this configuration, the concentrate from the concentrate outlet of the hydrophobic membrane module 2 can return to the feed tank 1 and be circulated and filtered by the hydrophobic membrane module 2, thereby improving the treatment capacity of the acidic low-level radioactive wastewater treatment system.

[0091] In one embodiment, the acidic low-level radioactive waste treatment system further includes a refrigeration unit. The refrigeration unit has a coolant inlet and a coolant outlet. The coolant outlet is connected to the cold-side inlet of the condenser 4. The coolant inlet is connected to the cold-side outlet of the condenser 4. The refrigeration unit is capable of introducing coolant into the condenser 4 to condense the vapor output from the permeate side of the hydrophobic membrane assembly 2. The refrigeration unit is preferably, but not limited to, a cooling tower, etc.

[0092] In one embodiment, the hydrophobic membrane assembly 2 includes a housing, a hollow fiber membrane bundle, and a plurality of baffles. The housing has a raw water inlet and a concentrate outlet. The hollow fiber membrane bundle is disposed within the housing, with a first end forming a permeate side and a second end sealed. The plurality of baffles are spaced apart within the housing, and the hollow fiber membrane bundle passes through the baffles, which are adapted to form a serpentine water path within the housing.

[0093] In this embodiment, during use, acidic low-level radioactive waste liquid can enter the shell side of the hydrophobic membrane module 2 through the raw water inlet on the outer shell. The negative pressure mechanism 6 can draw negative pressure on the hollow fiber membrane bundle, thereby promoting the water vapor generated by the acidic waste liquid in the shell side of the hydrophobic membrane module 2 to pass through the hollow fiber membrane fibers for filtration and enter the hollow fiber membrane fibers, and then flow out through the permeate side. The baffle can increase the flow velocity of the acidic low-level radioactive waste liquid in the shell side, so that the acidic low-level radioactive waste liquid can be in a turbulent state in the shell side. The boundary layer thickness between the acidic low-level radioactive waste liquid and the hollow fiber membrane fibers is thinned, improving the efficiency of mass transfer and heat transfer, thereby significantly improving the membrane flux of the hydrophobic membrane module 2.

[0094] Furthermore, the hydrophobic membrane component 2 in this embodiment is an externally pressurized type, which increases the mass transfer area and provides greater overall strength to the hollow fiber membrane filaments. Since the acidic low-level radioactive waste liquid is located within the shell side of the hydrophobic membrane component 2, the waste liquid exhibits good flowability, reducing the risk of impurities precipitated from the waste liquid clogging the hollow fiber membrane filaments and thus extending the service life of the hydrophobic membrane component 2. The hollow fiber membrane filaments are preferably, but not limited to, made of polytetrafluoroethylene (PTFE).

[0095] Membrane distillation technology is difficult to apply in the field of spent fuel waste treatment due to its low membrane flux. This solution uses a negative pressure mechanism to evacuate the hydrophobic membrane and sets up baffles to make the acidic low-level radioactive waste liquid turbulent, which can significantly improve the membrane flux. Thus, it can achieve high-fold concentration of radioactive waste liquid and reduce the final volume of radioactive waste liquid without reducing the treatment efficiency of acidic low-level radioactive waste liquid.

[0096] In one embodiment, the heating assembly includes a solar collector 701, a circulating water tank 702, a fluid drive mechanism 703, and a heat exchange preheater 704. The inlet of the circulating water tank 702 is connected to the outlet of the solar collector 701. The outlet of the circulating water tank 702 is connected to the inlet of the solar collector 701. The inlet of the fluid drive mechanism 703 is connected to the outlet of the circulating water tank 702. The hot-side inlet of the heat exchange preheater 704 is connected to the outlet of the fluid drive mechanism 703. The hot-side outlet of the heat exchange preheater 704 is connected to the circulating water tank 702, the cold-side inlet is adapted to receive acidic low-level radioactive waste liquid, and the cold-side outlet of the heat exchange preheater 704 is connected to the feeding tank 1.

[0097] The solar collector 701 can heat the water in the circulating water tank 702 to above 90°C. The heated liquid enters the circulating water tank 702 and is driven by the fluid drive mechanism 703 to the hot side inlet of the heat exchange preheater 704. It then flows back into the circulating water tank 702 through the hot side outlet and returns to the inlet of the solar collector through the outlet of the circulating water tank 702 for repeated heating. The cold side of the heat exchange preheater 704 can receive acidic low-level radioactive waste liquid and exchange heat between the acidic low-level radioactive waste liquid and the hot water in the circulating water tank 702. The cold side outlet temperature of the heat exchange preheater 704 is approximately 70°C to 80°C.

[0098] Among them, the heat exchange preheater 704 is preferably, but not limited to, a shell and tube heat exchanger.

[0099] In one embodiment, the heating assembly further includes a semi-circular tube jacketed container 705. The semi-circular tube jacketed container 705 is fitted onto the outside of the feeding tank 1 and is suitable for connecting to a steam source. In winter and at night, the solar collector 701 may not adequately heat the liquid in the feeding tank 1; the semi-circular tube jacketed container 705 can supplement the heating of the acidic low-level radioactive waste liquid in the feeding tank 1 using a high-temperature steam source. The semi-circular tube jacketed container 705 is preferably, but not limited to, a DN60 semi-circular tube jacket.

[0100] As an alternative implementation, the outer side of the feeding trough 1 may be equipped with an electric heater.

[0101] In one embodiment, the heating assembly includes a steam pipe. The steam pipe is arranged around the outside of the feed trough 1, and its inlet end is connected to the condensate main of the power plant, enabling the feed trough 1 to be heated using waste heat from the power plant.

[0102] In one embodiment, the heating assembly includes an electromagnetic coil and a frequency converter heating controller. The electromagnetic coil is arranged around the outside of the feeding trough 1, and the frequency converter heating controller is communicatively connected to the electromagnetic coil.

[0103] It should be noted that the above-described embodiments of the heating component are merely preferred embodiments of the heating component of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art can easily make changes or modifications within the scope of the technology disclosed in the present invention, and such changes or modifications should be covered within the scope of protection of the present invention.

[0104] In one embodiment, the fluid drive mechanism 703 is a circulating water pump, and the outlet of the feed trough is higher than the inlet of the circulating water pump to prevent cavitation. Preferably, the height difference between the inlet and outlet of the circulating water pump is greater than 1.5m.

[0105] In one embodiment, the acidic low-level radioactive waste liquid treatment system further includes an exhaust gas treatment device 8, which is connected to the output end of the negative pressure mechanism 6 and can remove radioactive elements from the exhaust gas to prevent the leakage of radioactive elements and environmental pollution.

[0106] In one embodiment, the exhaust gas treatment device 8 further includes a demister 801, a heater 802, and a filter assembly 803. The demister 801 is connected to the output of the negative pressure mechanism 6. The inlet of the heater 802 is connected to the outlet of the demister 801, and is suitable for increasing the exhaust gas temperature and reducing the exhaust gas humidity. The inlet of the filter assembly 803 is connected to the outlet of the heater 802.

[0107] The permeate vapor extracted by the vacuum pump contains not only condensed portion but also some non-condensable gases. These non-condensable gases mix with the condensate in condenser 4. After being drawn into the vacuum pump, the gas will carry droplets containing radioactive nuclides. Direct release into the atmosphere would cause radioactive contamination; therefore, a purification unit is required. The demister 801 can remove radioactive droplets from the exhaust gas with a removal efficiency of ≥99%.

[0108] The demister 801 is preferably, but not limited to, made of glass fiber, and is capable of removing radioactive droplets entrained in the exhaust gas. Since the filter assembly 803 is made of glass fiber paper, if the moisture content in the exhaust gas is high and close to the dew point temperature, condensation will occur, wetting the glass fiber paper and causing the high-efficiency filter assembly 803 to fail. Therefore, a heater 802 is needed to increase the temperature difference with the dew point and reduce the moisture content. The heater 802 is preferably, but not limited to, a pipe-type electric heater 802, capable of heating the exhaust gas to 80–120°C to increase the exhaust gas temperature and reduce its humidity. The filter assembly 803 is preferably, but not limited to, made of glass fiber, and is capable of removing radioactive nuclides carried in the exhaust gas. Preferably, the exhaust gas treatment device 8 also includes an exhaust gas fan, which is connected to the outlet of the filter assembly 803 and is suitable for conveying the purified exhaust gas to the chimney. The fan is a vortex fan with an inlet negative pressure of -20 kPa and an outlet pressure of 2 kPa.

[0109] In one embodiment, the acidic low-level radioactive waste treatment system further includes a transfer pump 7. The input end of the transfer pump 7 is connected to the outlet of the feed tank 1, and the output end of the transfer pump 7 is connected to the inlet of the membrane module. The transfer pump 7 not only facilitates the flow of acidic low-level radioactive waste from the feed tank 1 to the membrane module, but also, after the transfer pump 7 inputs the acidic low-level radioactive waste into the membrane module, there is a certain pressure loss. A circulation pipeline can be formed between the feed tank 1, the transfer pump 7, and the hydrophobic membrane module 2, so that the concentrated solution at the outlet of the hydrophobic membrane module 2 returns to the feed tank 1.

[0110] In one embodiment, the input end of the negative pressure mechanism 6 is connected to the hot-side outlet of the condenser 4. With this configuration, the negative pressure mechanism 6 can not only facilitate water vapor to pass through the membrane pores of the hydrophobic membrane assembly 2 into the permeate side of the hydrophobic membrane assembly 2 to increase the membrane flux of the hydrophobic membrane assembly 2, but also facilitate the vapor on the permeate side of the hydrophobic membrane assembly 2 to enter the hot-side inlet of the condenser 4, so that the vapor passes through the condenser 4 and is condensed into condensate.

[0111] According to an embodiment of the present invention, another aspect provides a method for treating acidic low-level radioactive waste liquid, applied to an acidic low-level radioactive waste liquid treatment system. The acidic low-level radioactive waste liquid treatment system includes a feeding tank 1, a heating component, a hydrophobic membrane component 2, a condenser 4, a condensate tank 5, and a negative pressure mechanism 6. The feeding tank 1 is adapted to contain the acidic low-level radioactive waste liquid. The heating component is adapted to heat the acidic low-level radioactive waste liquid in the feeding tank 1. The raw water outlet of the feeding tank 1 is connected to the input end of the hydrophobic membrane component 2. The hot-side inlet of the condenser 4 is connected to the permeate side of the hydrophobic membrane component 2. The condensate tank 5 is connected to the hot-side outlet of the condenser 4. The negative pressure mechanism 6 is connected to the permeate side of the hydrophobic membrane component 2 and is adapted to evacuate the permeate side of the hydrophobic membrane component 2.

[0112] like Figure 2 As shown, the method for treating acidic low-level radioactive waste liquid includes steps S1, S2, S3, and S4.

[0113] Step S1: Control the heating component to heat the acidic low-level radioactive waste liquid in the feeding tank 1 to the first preset temperature;

[0114] Step S2: The heated acidic low-level radioactive waste liquid is transported into the hydrophobic membrane module 2;

[0115] Step S3: Control the negative pressure mechanism 6 to draw negative pressure on the permeation side of the hydrophobic membrane assembly 2 so that the permeation side of the hydrophobic membrane assembly 2 reaches the preset pressure.

[0116] Step S4: Control the condenser 4 to cool the vapor on the permeation side of the hydrophobic membrane assembly 2, condense the vapor into condensate and collect it in the condensate tank 5.

[0117] The acidic low-level radioactive waste liquid treatment method of the second aspect of the present invention uses the acidic waste liquid treatment system of the first aspect of the present invention, and therefore has its beneficial effects, namely: the acidic low-level radioactive waste liquid treatment method of the present invention can treat acidic low-level radioactive waste liquid, has a good concentration effect, and does not cause equipment corrosion.

[0118] In one embodiment, the preset temperature is T1, where 70℃≤T1≤80℃. This setting allows the acidic low-level radioactive waste liquid in the feeding tank 1 to enter the hydrophobic membrane component 2 in the form of steam without boiling. The hydrophobic membrane component 2 can retain nitric acid and radionuclides in the acidic low-level radioactive waste liquid treatment system without causing concentrated nitric acid to accelerate equipment corrosion in a boiling state.

[0119] In one embodiment, the acidic low-level radioactive waste treatment system further includes a transfer pump 7. The input end of the transfer pump 7 is connected to the outlet of the feed tank 1, and the output end of the transfer pump 7 is connected to the inlet of the membrane module.

[0120] Step S2 also includes: controlling the delivery pump 7 to make the flow rate at the input end of the hydrophobic membrane assembly 2 reach the preset flow rate.

[0121] Preferably, the preset flow rate is Q, where 400 L / h ≤ Q ≤ 600 L / h. In a more preferred embodiment, the circulation flow rate of the transfer pump 7 is 600 L / h. The higher the circulation flow rate of the transfer pump 7, the higher the flow velocity of the acidic low-level radioactive waste liquid, which can be in a turbulent state. The boundary layer thickness between the acidic low-level radioactive waste liquid and the hydrophobic membrane component 2 becomes thinner, thereby improving the efficiency of mass and heat transfer, and thus significantly improving the membrane flux.

[0122] In one embodiment, the preset pressure is P, where 6 kPa ≤ P ≤ 15 kPa. Calculations show that when the preset pressure is within the above range, after multiple cycles, the nitric acid concentration in the waste liquid in the feed tank 1 is concentrated to a high level. The partial pressure of concentrated nitric acid vapor at 70-80°C is 5.7 kPa. This is because the vacuum side pressure must be higher than the partial pressure of the highest concentration of concentrated nitric acid; otherwise, a large amount of nitric acid will permeate through the hydrophobic membrane.

[0123] In one embodiment, the acidic low-level radioactive wastewater treatment system further includes a refrigeration unit having a coolant inlet and a coolant outlet, the coolant outlet being connected to the cold-side inlet of the condenser 4. The coolant inlet is connected to the cold-side outlet of the condenser 4. Step S4 further includes controlling the refrigeration unit to introduce coolant into the condenser 4. The coolant temperature at the cold-side inlet is a second preset temperature, and the coolant temperature at the cold-side outlet is a third preset temperature. Preferably, the second preset temperature is 10°C, and the third preset temperature is 20°C. The vapor drawn from the cold side is cooled into condensate in the condenser 4 and collected in a condensate tank 5. The purified liquid in the condensate tank 5 has a pH ≥ 4.

[0124] In one embodiment, the method for treating acidic low-level radioactive waste liquid further includes step S5: adjusting the pH value of the condensate using an alkaline solution.

[0125] After processing a batch of liquid material, the purified liquid needs to be neutralized with a 20% sodium hydroxide solution. The treatment target is achieved when the pH in the condensate tank 5 is 6-7, the radioactivity βγ ≤ 40 Bq / L, and α ≤ 4 Bq / L.

[0126] Although embodiments of the invention have been described in conjunction with the accompanying drawings, those skilled in the art can make various modifications and variations without departing from the spirit and scope of the invention, and such modifications and variations all fall within the scope defined by the appended claims.

Claims

1. A method for treating acidic low-level radioactive waste liquid, characterized in that, An application is made in an acidic low-level radioactive waste liquid treatment system, the acidic low-level radioactive waste liquid treatment system comprising: Feed tank (1) is suitable for containing acidic low-level radioactive waste liquid; A heating assembly adapted to heat the acidic low-level radioactive waste liquid in the feed tank (1); The hydrophobic membrane assembly (2) has its raw water outlet connected to the input end of the feed tank (1); The condenser (4) has its hot-side inlet connected to the permeation side of the hydrophobic membrane assembly (2); A condensate tank (5) is connected to the hot-side outlet of the condenser (4); A negative pressure mechanism (6) is connected to the permeation side of the hydrophobic membrane assembly (2) and is adapted to evacuate the permeation side of the hydrophobic membrane assembly (2). The input end of the negative pressure mechanism (6) is connected to the hot side outlet of the condenser (4); The method for treating acidic low-level radioactive waste liquid includes: The heating assembly is controlled to heat the acidic low-level radioactive waste liquid in the feeding tank (1) to a first preset temperature; The heated acidic low-level radioactive waste liquid is transported into the hydrophobic membrane module (2); The negative pressure mechanism (6) is controlled to draw negative pressure on the permeation side of the hydrophobic membrane assembly (2) so that the permeation side of the hydrophobic membrane assembly (2) reaches a preset pressure. The condenser (4) is controlled to cool the vapor on the permeation side of the hydrophobic membrane assembly (2), condensing the vapor into condensate and collecting it in the condensate tank (5); The first preset temperature is T1, 70℃≤T1≤80℃; the preset pressure is P, 6kpa≤P≤15kpa; The acidic low-level radioactive waste liquid contains nitric acid and radionuclides.

2. The method for treating acidic low-level radioactive waste liquid according to claim 1, characterized in that, The acidic low-level radioactive waste treatment system also includes a transfer pump (7), the input end of which is connected to the outlet of the feed tank (1), and the output end of which is connected to the inlet of the hydrophobic membrane assembly (2). The step of conveying the heated acidic low-level radioactive waste liquid into the hydrophobic membrane module (2) further includes: Control the delivery pump (7) to make the flow rate at the input end of the hydrophobic membrane assembly (2) reach the preset flow rate.

3. The method for treating acidic low-level radioactive waste liquid according to claim 2, characterized in that, The preset flow rate is Q, where 400L / h ≤ Q ≤ 600L / h.

4. The method for treating acidic low-level radioactive waste liquid according to claim 1, characterized in that, Also includes: The pH value of the condensate is adjusted using an alkaline solution.

5. The method for treating acidic low-level radioactive waste liquid according to claim 1, characterized in that, The concentrated liquid outlet of the hydrophobic membrane assembly (2) is connected to the feed tank (1).

6. The method for treating acidic low-level radioactive waste liquid according to claim 1, characterized in that, The hydrophobic membrane assembly (2) includes: The outer shell has a raw water inlet and a concentrate outlet. A hollow fiber membrane bundle is disposed inside the housing, wherein a first end of the hollow fiber membrane bundle forms a permeation side and a second end is sealed; Multiple baffles are spaced apart within the housing, and the hollow fiber membrane bundle passes through the multiple baffles, which are adapted to form a serpentine waterway within the housing.

7. The method for treating acidic low-level radioactive waste liquid according to any one of claims 1 to 6, characterized in that, The heating component includes: Solar collector (701); The inlet of the circulating water tank (702) is connected to the outlet of the solar collector (701), and the outlet of the circulating water tank (702) is connected to the inlet of the solar collector (701). A fluid drive mechanism (703) has its inlet connected to the outlet of the circulating water tank (702); The heat exchange preheater (704) has its hot side inlet connected to the outlet of the fluid drive mechanism (703), its hot side outlet connected to the circulating water tank (702), its cold side inlet adapted to receive acidic low-level radioactive waste liquid, and its cold side outlet connected to the feeding tank (1).

8. The method for treating acidic low-level radioactive waste liquid according to claim 7, characterized in that, The heating component includes: A semi-circular tube jacketed container (705) is fitted on the outside of the feed trough (1) and is suitable for connecting to a steam source.

9. The method for treating acidic low-level radioactive waste liquid according to claim 7, characterized in that, The fluid drive mechanism (703) is a circulating water pump, and the outlet of the feeding tank (1) is higher than the inlet of the circulating water pump.

10. The method for treating acidic low-level radioactive waste liquid according to any one of claims 1 to 6, characterized in that, The heating assembly includes a steam pipe that surrounds the outside of the feed trough (1), and the steam inlet is connected to the condensate main of the power plant; or, The heating assembly includes an electromagnetic coil and a frequency converter heating controller. The electromagnetic coil is arranged around the outside of the feeding trough (1), and the frequency converter heating controller is communicatively connected to the electromagnetic coil.

11. The method for treating acidic low-level radioactive waste liquid according to any one of claims 1 to 6, characterized in that, It also includes an exhaust gas treatment device (8), which is connected to the output end of the negative pressure mechanism (6).

12. The method for treating acidic low-level radioactive waste liquid according to claim 11, characterized in that, The exhaust gas treatment device (8) includes: A demister (801) is connected to the output end of the negative pressure mechanism (6); A heater (802) has its inlet connected to the outlet of the demister (801); The filter assembly (803) has its inlet connected to the outlet of the heater (802).

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