Negative pressure heat pump evaporation treatment system for radioactive waste liquid

Abstract

The invention discloses a negative pressure heat pump evaporation treatment system for radioactive waste liquid, comprising: a heating evaporation unit comprising: a steam generator, a waste liquid inlet of which is used to introduce radioactive waste liquid, a waste liquid outlet of which is connected to a circulation pipe, and a heating steam outlet is connected to a startup heating steam inlet; an evaporator, comprising: a heating chamber, a separation chamber, a purification chamber, a circulation pipe, a heating chamber waste liquid circulation outlet is connected to a separation chamber waste liquid circulation inlet, the separation chamber is connected to the purification chamber, the heating chamber waste liquid circulation inlet and the separation chamber waste liquid circulation outlet are connected via a circulation pipe, and a startup heating steam inlet is connected to a heating steam outlet; a compressor, an inlet of which is connected to a secondary steam outlet, and an outlet of which is connected to a compressed secondary steam inlet. When the system in the invention is started, the steam generator is used to heat the radioactive waste liquid to generate steam, which is introduced into the heating chamber tube side through a pipeline, directly heats the radioactive waste liquid and promotes the circulation of the feed liquid, shortens the start-up time, and avoids the generation of secondary pollutants during the start-up process.

Description

Technical Field

[0001] The invention belongs to the technical field of radioactive waste treatment, and in particular relates to a lithium nickel manganese oxygen material and a radioactive waste liquid negative pressure heat pump evaporation treatment system. Background Art

[0002] As an effective means of treating radioactive liquid waste, evaporation is widely used in the nuclear industry. In recent years, heat pump evaporation has become a research hotspot in radioactive liquid waste treatment technology due to its superior energy-saving and consumption-reducing effects. Heat pump evaporation to treat radioactive liquid waste uses a compressor to recompress the secondary steam generated by the evaporator itself, and the low-grade steam is upgraded to high-grade steam through the mechanical work of the compressor, and then used to heat and evaporate the raw liquid of the system.

[0003] Commonly used heat pump evaporation technologies include natural circulation and forced circulation heat pump evaporation. The forced circulation heat pump evaporator is composed of a heating chamber, a separation chamber and a compressor, which are connected into a whole by a circulation pipe and a circulation pump. The circulation pump allows the waste liquid in the circulation pipe between the separation chamber and the heating chamber to circulate quickly, so the heat transfer coefficient is high and the heat exchange area is reduced. However, the forced circulation pump is driven by an electric motor, which consumes a lot of power, makes a lot of noise, and requires frequent maintenance and repair. Therefore, in the field of nuclear facilities, the application of forced circulation evaporation technology is limited. Compared with the forced circulation heat pump evaporator, the natural circulation heat pump evaporator does not require a power pump circulation, which reduces power consumption, leakage risk and maintenance, as well as the radiation dose of the operating personnel. Therefore, for radioactive waste liquid treatment systems that are not easy to scale, natural circulation heat pump evaporators are more suitable.

[0004] At present, the domestic radioactive waste liquid heat pump evaporation treatment technology is still in the initial research stage and there is no successful engineering application.

[0005] During the process of treating radioactive waste liquid with heat pump evaporation technology, the non-condensable gas in the waste liquid will be evaporated. This part of the non-condensable gas must be continuously and quickly discharged from the system, otherwise the impurity gas content of the distillate will exceed the standard. At this time, a certain amount of steam is required to carry the non-condensable gas to ensure the smooth flow of the non-condensable gas. This will cause the humidity and temperature of the non-condensable gas to be high. Therefore, the high-temperature and high-humidity non-condensable gas must be cooled and dehumidified before being discharged, otherwise it will seriously affect the service life of the filter of the subsequent radioactive ventilation system. However, there is little research on the treatment and recycling of non-condensable gas.

[0006] Moreover, in the prior art, the condensate from the non-condensable gas is directly discharged or reused. However, the author has found that the heat pump evaporation process will cause the non-condensable gas temperature to be higher due to excessive heat supply, resulting in a higher partial pressure of impurity gases in the non-condensable gas flow, and a higher content of impurity gases dissolved in the entrained steam condensate. For systems with stricter requirements for the quality of discharged or reused distillates, such as the ultra-low oxygen content requirement for distillates in the boron recycling system of nuclear power plants, the impurity gas content of the distillate will increase sharply, and it is very easy to cause the quality of the distillate to be unqualified.

[0007] In the publicly available technical research, the author analyzed that there are still the following problems:

[0008] a) It requires supporting public systems, which are complex and have poor independence;

[0009] b) A large amount of secondary waste liquid or secondary waste gas is often generated during the treatment process, which reduces the energy-saving and emission-reduction effect of the system;

[0010] c) It takes a long time to establish a stable production state, which is not conducive to the emergency treatment of radioactive waste liquid in the event of an emergency or emergency situation in a nuclear power plant;

[0011] d) There is still room for further improvement in the quality of the final product.

[0012] The above problems and shortcomings restrict the promotion and application of heat pump evaporation technology in the nuclear industry. Summary of the invention

[0013] The technical problem to be solved by the present invention is to provide a radioactive waste liquid negative pressure heat pump evaporation treatment system in view of the above-mentioned deficiencies in the prior art, which effectively shortens the startup time, avoids the generation of secondary pollutants during the startup process, and simplifies the system structure.

[0014] The technical solution adopted to solve the technical problem of the present invention is to provide a radioactive waste liquid negative pressure heat pump evaporation treatment system, including: a heating evaporation unit, used to evaporate the radioactive waste liquid, the heating evaporation unit includes:

[0015] A steam generator is used to heat radioactive waste liquid to generate heating steam. A steam generator waste liquid inlet is provided at the upper portion of the steam generator for introducing radioactive waste liquid, a steam generator waste liquid outlet at the lower portion is connected to a circulation pipe, and a heating steam outlet is also provided at the upper portion of the steam generator for connecting to a start-up heating steam inlet at the lower portion of the heating chamber tube side;

[0016] The evaporator comprises: a heating chamber, a separation chamber, a purification chamber, and a circulation pipe, wherein the heating chamber waste liquid circulation outlet on the upper end tube side of the heating chamber is connected to the separation chamber waste liquid circulation inlet of the separation chamber, the upper part of the separation chamber is connected to the lower part of the purification chamber, the heating chamber waste liquid circulation inlet at the lower part of the heating chamber tube side and the separation chamber waste liquid circulation outlet at the lower part of the separation chamber are connected via the circulation pipe, the start-up heating steam inlet on the heating chamber tube side is connected to the heating steam outlet of the steam generator, and the heating steam generated in the steam generator is introduced into the tube side in the heating chamber to heat the radioactive waste liquid in the tube side;

[0017] A compressor, the compressor inlet is connected to the secondary steam outlet at the top of the purification chamber, and the compressor outlet is connected to the compressed secondary steam inlet on the shell side of the heating chamber.

[0018] Preferably, the negative pressure heat pump evaporation treatment system for radioactive waste liquid further comprises:

[0019] A non-condensable gas recovery and treatment unit is used for recovering and treating non-condensable gas, and the non-condensable gas flow outlet on the shell side of the heating chamber is connected to the non-condensable gas recovery and treatment unit;

[0020] The distillate recovery and utilization unit is used for distillate recovery and utilization. The distillate outlet on the shell side of the heating chamber is connected to the distillate recovery and utilization unit.

[0021] Preferably, the non-condensable gas recovery and treatment unit includes: a non-condensable gas heat exchanger and a non-condensable gas cooler, which respectively recover waste heat and cool and dehumidify the non-condensable gas flow of the system; the waste liquid inlet of the steam generator is connected to the shell side outlet of the non-condensable gas heat exchanger; the shell side inlet of the non-condensable gas heat exchanger is used to introduce radioactive waste liquid; the shell side non-condensable gas flow outlet of the heating chamber is connected to the non-condensable gas flow inlet of the heat exchanger on the lower tube side of the non-condensable gas heat exchanger; a heat exchanger non-condensable gas flow outlet is provided on the upper tube side of the non-condensable gas heat exchanger; the non-condensable gas flow outlet of the heat exchanger is connected to the non-condensable gas cooler; and a steam condensate discharge outlet is provided at the bottom of the non-condensable gas heat exchanger and is connected to the circulation pipe.

[0022] Preferably, the distillate recovery and utilization unit includes: a distillate receiving tank, a distillate pump, and a distillate heat exchanger. A distillate receiving port is provided at the top of the distillate receiving tank, and the distillate receiving port is connected to the distillate outlet on the shell side of the heating chamber. A distillate receiving tank pressure balance port is also provided at the top of the distillate receiving tank, and the distillate receiving tank pressure balance port is connected to the upper pressure balance port on the shell side of the heating chamber. The lower end outlet of the distillate receiving tank is connected to the distillate pump, and the distillate pump outlet is connected to the shell side inlet of the distillate heat exchanger. The tube side inlet of the distillate heat exchanger is used to input radioactive waste liquid, and the tube side outlet of the distillate heat exchanger is connected to the shell side inlet of the non-condensable gas heat exchanger.

[0023] Preferably, the distillate pump outlet is also connected to the pipeline between the compressor outlet and the compressed secondary steam inlet, the distillate pump outlet is also connected to the partial reflux inlet of the distillate at the top of the purification chamber, and the distillate pump outlet is also connected to the full reflux inlet of the distillate at the top of the separation chamber.

[0024] Preferably, the heating evaporation unit further comprises: a pressure regulating valve and a pressure sensor arranged on the top of the steam generator, and the pressure regulating valve and the pressure sensor are connected to form a regulating loop.

[0025] Preferably, the heating evaporation unit also includes: a differential pressure density meter and a differential pressure level meter arranged in the separation chamber, the upper and lower ends of the differential pressure density meter are located below the liquid level of the concentrated liquid in the separation chamber and are installed close to the inner wall of the separation chamber; the differential pressure level meter is used to receive the transmitted density value of the differential pressure density meter and feedback the accurate liquid level value according to the relationship between the pressure difference and the liquid level.

[0026] Preferably, the upper portion of the separation chamber is connected to the lower portion of the purification chamber, and the separation chamber and the purification chamber are an integrated structure.

[0027] Preferably, the operating pressure of the evaporator is 60 kPaA-85 kPaA, and the operating temperature is 86°C-95°C.

[0028] Preferably, the purification chamber comprises, from bottom to top, a baffle demister, a deep purification zone, and a wire mesh demister, and the deep purification zone is a multi-layer tower plate structure or a packing structure.

[0029] Preferably, the non-condensable gas heat exchanger is a vertical structure, the non-condensable gas flow hot fluid and the radioactive waste liquid cold fluid in the non-condensable gas heat exchanger adopt countercurrent heat exchange, and the non-condensable gas flow enters from the non-condensable gas flow inlet of the lower tube side heat exchanger of the non-condensable gas heat exchanger.

[0030] The radioactive waste liquid negative pressure heat pump evaporation treatment system of the present invention utilizes a steam generator to heat the radioactive waste liquid to generate steam when starting the machine, and the steam is passed into the pipe side of the heating chamber through a pipeline to directly heat the radioactive waste liquid and promote the circulation of the feed liquid, thereby effectively shortening the start-up time, avoiding the generation of secondary pollutants during the start-up process, simplifying the system structure, and improving the independence, integrity and adaptability of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is a simplified flow chart of the external heating type radioactive waste liquid negative pressure heat pump evaporation treatment system in Example 2 of the present invention;

[0032] Figure 2 This is a schematic diagram of the clean room structure of the system in Example 2 of the present invention;

[0033] Figure 3 This is a schematic diagram of the separation chamber structure of the system in Example 2 of the present invention;

[0034] Figure 4 This is a schematic diagram of the heating chamber structure of the system in Example 2 of the present invention;

[0035] Figure 5 This is a schematic diagram of the structure of the non-condensable gas treatment unit of the system in Example 2 of the present invention;

[0036] Figure 6 This is a schematic diagram of the steam generator structure of the system in Example 2 of the present invention.

[0037] In the figure: 1--purification chamber, 2--separation chamber, 3--heating chamber, 4--compressor, 5--steam generator, 6--distillate receiving tank, 7--distillate pump, 8--circulation pipe, 9--distillate heat exchanger, 10--non-condensable gas heat exchanger, 12--non-condensable gas cooler, 13--deep purification area, 14--liquid level meter, 15--density meter, 20--concentrated liquid discharge pipeline, 21--secondary steam pipeline, 22--compressed secondary steam pipeline, 24-distillate collection pipeline, 25-distillate pump inlet pipeline, 26--distillate total recycling pipeline, 2 7--Distillate waste heat recovery pipeline, 28--Distillate discharge pipeline, 31--Waste liquid feeding pipeline, 32--Waste liquid feeding regulating valve, 33--Heat exchanger connecting pipeline, 34--Steam generator feeding pipeline, 36--Steam generator discharge pipeline, 37--Heating steam pipeline, 38--Heating steam regulating valve, 39--Non-condensable gas flow pipeline, 40--Entrained steam condensate pipeline, 41--Non-condensable gas cooler feeding pipeline, 42--Non-condensable gas discharge pipeline, 43--Concentrate discharge outlet, 44--Circulation pipe waste liquid inlet, 45--Entrained steam condensate inlet , 50--superheated water inlet, 51--superheated water pipeline, 52--distillate reflux pipeline, 55--distillate full reflux pipeline, 56--distillate receiving tank pressure balance pipeline, 57--distillate receiving port, 58--distillate receiving tank pressure balance port, 101--secondary steam outlet, 102--distillate partial reflux liquid inlet, 103--baffle demister, 104--wire mesh demister, 201--separation chamber waste liquid circulation outlet, 202--separation chamber waste liquid circulation inlet, 203--full reflux inlet, 301--heating chamber waste liquid circulation inlet Inlet, 302--heating chamber waste liquid circulation outlet, 303--start-up heating steam inlet, 304--distillate outlet, 305-non-condensable gas flow outlet, 306--compressed secondary steam inlet, 307--heat exchange tube of heating chamber, 308--pressure balance port, 501--heating steam outlet, 502--steam generator waste liquid outlet, 503--steam generator waste liquid inlet, 505--steam generator pressure regulation control loop, 1001--entrained steam condensate discharge outlet, 1002--heat exchanger non-condensable gas flow inlet, 1003--heat exchanger non-condensable gas flow outlet. DETAILED DESCRIPTION

[0038] In order to enable those skilled in the art to better understand the technical solution of the present invention, the present invention is further described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0039] The embodiments of the present invention are described in detail below, and examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and cannot be understood as limiting the present invention.

[0040] Example 1

[0041] This embodiment provides a radioactive waste liquid negative pressure heat pump evaporation treatment system, including: a heating evaporation unit, used to evaporate the radioactive waste liquid, the heating evaporation unit includes:

[0042] A steam generator is used to heat radioactive waste liquid to generate heating steam. A steam generator waste liquid inlet is provided at the upper portion of the steam generator for introducing radioactive waste liquid, a steam generator waste liquid outlet at the lower portion is connected to a circulation pipe, and a heating steam outlet is also provided at the upper portion of the steam generator for connecting to a start-up heating steam inlet at the lower portion of the heating chamber tube side;

[0043] The evaporator comprises: a heating chamber, a separation chamber, a purification chamber, and a circulation pipe, wherein the heating chamber waste liquid circulation outlet on the upper end tube side of the heating chamber is connected to the separation chamber waste liquid circulation inlet of the separation chamber, the upper part of the separation chamber is connected to the lower part of the purification chamber, the heating chamber waste liquid circulation inlet at the lower part of the heating chamber tube side and the separation chamber waste liquid circulation outlet at the lower part of the separation chamber are connected via the circulation pipe, the start-up heating steam inlet on the heating chamber tube side is connected to the heating steam outlet of the steam generator, and the heating steam generated in the steam generator is introduced into the tube side in the heating chamber to heat the radioactive waste liquid in the tube side;

[0044] A compressor, the compressor inlet is connected to the secondary steam outlet at the top of the purification chamber, and the compressor outlet is connected to the compressed secondary steam inlet on the shell side of the heating chamber.

[0045] The radioactive waste liquid negative pressure heat pump evaporation treatment system in this embodiment utilizes a steam generator to heat the radioactive waste liquid to generate steam when starting up, and the steam is passed into the tube side of the heating chamber through a pipeline to directly heat the radioactive waste liquid and promote the circulation of the feed liquid, thereby effectively shortening the startup time, avoiding the generation of secondary pollutants during the startup process, simplifying the system structure, and improving the independence, integrity and adaptability of the system.

[0046] Example 2

[0047] like Figures 1 to 6 As shown, this embodiment provides a radioactive waste liquid negative pressure heat pump evaporation treatment system, including: a heating evaporation unit, used to evaporate the radioactive waste liquid, the heating evaporation unit includes:

[0048] The steam generator 5 is used to generate startup steam and supplement heat during the operation of the production process. The steam generator 5 is provided with a steam generator waste liquid inlet 503 and a heating steam outlet 501 at the top, and a steam generator waste liquid outlet 502 at the bottom. The steam generator 5 is provided with a steam generator waste liquid inlet 503 at the top for introducing radioactive waste liquid. The steam generator waste liquid inlet 503 is connected to the waste liquid outlet of the non-condensable gas heat exchanger 10 through the steam generator feed pipe 34. The lower steam generator waste liquid outlet 502 is connected to the circulation pipe waste liquid inlet 44 on the circulation pipe 8 through the steam generator discharge pipe 36. The steam generator 5 is also provided with a heating steam outlet 501 at the top, which is connected to the startup heating steam inlet 303 at the bottom of the heating chamber 3 tube side through the heating steam pipe 37. A heating steam regulating valve 38 is provided on the heating steam pipe 37, and a heating chamber heat exchange pipe 307 is provided in the heating chamber 3.

[0049] The evaporator is used for separating and concentrating radioactive waste liquid, and comprises: a heating chamber 3, a separation chamber 2, a purification chamber 1, and a circulation pipe 8. The heating chamber 3 is used for heating the waste liquid in the heat exchange pipe 307 of the heating chamber to partially vaporize it and generate secondary steam, wherein the natural circulation driving force of the waste liquid in the evaporator is formed due to the density difference between the vapor-liquid two-phase mixture in the heat exchange pipe 307 of the heating chamber and the waste liquid in the circulation pipe 8. The separation chamber 2 is used for the preliminary separation of secondary steam and waste liquid. The purification chamber 1 is used for eliminating the entrainment of mist and foam in the secondary steam and deeply purifying the secondary steam. The upper part of the side wall of the separation chamber 2 is provided with a full reflux inlet 203 of the distillate, the upper part of the purification chamber 1 is provided with a partial reflux inlet 102 of the distillate, the circulation pipe 8 is provided with a circulation pipe waste liquid inlet 44, a concentrated liquid discharge outlet 43, and an entrained steam condensate inlet 45, and the concentrated liquid discharge outlet 43 is connected to the concentrated liquid discharge pipe 20; the outlet pipe of the compressor 4 is provided with a desuperheated water inlet 50. The heating chamber waste liquid circulation outlet 302 on the upper end tube side of the heating chamber 3 is connected to the separation chamber waste liquid circulation inlet 202 of the separation chamber 2, the upper part of the separation chamber 2 is connected to the lower part of the purification chamber 1, the heating chamber waste liquid circulation inlet 301 at the lower part of the tube side of the heating chamber 3 and the separation chamber waste liquid circulation outlet 201 at the lower part of the separation chamber 2 are connected via a circulation pipe 8, the inlet end of the circulation pipe 8 is connected to the separation chamber waste liquid circulation outlet 201 at the lower part of the separation chamber 2, the outlet end of the circulation pipe 8 is connected to the heating chamber waste liquid circulation inlet 301 at the lower part of the tube side of the heating chamber 3, the startup heating steam inlet 303 on the tube side of the heating chamber 3 is connected to the heating steam outlet 501 of the steam generator 5, the heating steam generated in the steam generator 5 is introduced into the tube side of the heating chamber 3 for heating the radioactive waste liquid in the tube side, and the separation chamber 2-circulation pipe 8-heating chamber 3-separation chamber 2 constitute a waste liquid natural circulation loop;

[0050] The compressor 4 is used to increase the temperature and pressure of the secondary steam generated by the evaporator, and the obtained high-grade steam is used to circulate and heat the waste liquid. The inlet of the compressor 4 is connected to the secondary steam outlet 101 at the top of the purification chamber 1 through the secondary steam pipeline 21, and the outlet of the compressor 4 is connected to the compressed secondary steam inlet 306 on the shell side of the heating chamber 3 through the compressed secondary steam pipeline 22. The concentrated liquid discharge port 43 on the circulation pipe 8 discharges the final concentrated liquid into the downstream concentrated liquid storage tank through the concentrated liquid discharge pipeline 20.

[0051] The heating evaporation unit also includes supporting pipelines.

[0052] Preferably, the negative pressure heat pump evaporation treatment system for radioactive waste liquid further comprises:

[0053] A non-condensable gas recovery and treatment unit is used for non-condensable gas recovery and treatment. The non-condensable gas flow outlet 305 on the shell side of the heating chamber 3 is connected to the non-condensable gas recovery and treatment unit;

[0054] The distillate recovery and utilization unit is used for distillate recovery and utilization. The distillate outlet 304 on the shell side of the heating chamber 3 is connected to the distillate recovery and utilization unit.

[0055] Preferably, the non-condensable gas recovery and treatment unit includes: a non-condensable gas heat exchanger 10 and a non-condensable gas cooler 12. The non-condensable gas heat exchanger 10 is used to preheat the waste liquid to a near-saturation temperature using the heat of the non-condensable gas flow, and the non-condensable gas cooler 12 is used to cool and dehumidify the high-temperature and high-humidity non-condensable gas flow. A non-condensable gas flow inlet 1002 is provided at the lower part of the tube side of the non-condensable gas heat exchanger 10, a heat exchanger non-condensable gas flow outlet 1003 is provided at the upper part of the tube side of the non-condensable gas heat exchanger 10, a waste liquid inlet is provided at the upper part of the shell side of the non-condensable gas heat exchanger 10, a waste liquid outlet is provided at the lower part, a non-condensable gas flow entrained steam condensate discharge outlet 1001 is also provided at the lower end of the tube side of the non-condensable gas heat exchanger 10, the steam generator waste liquid inlet 503 is connected to the shell side outlet of the non-condensable gas heat exchanger 10, the shell side inlet of the non-condensable gas heat exchanger 10 is used to introduce radioactive waste liquid, and the shell side non-condensable gas flow outlet 305 of the heating chamber 3 is connected to the non-condensable gas heat exchanger through the non-condensable gas flow pipeline 39 of the system. The non-condensable gas inlet 1002 of the heat exchanger at the lower tube side 10 is connected, and the non-condensable gas outlet 1003 of the heat exchanger is set at the upper tube side of the non-condensable gas heat exchanger. The non-condensable gas outlet 1003 of the heat exchanger is connected to the non-condensable gas cooler 12 through the non-condensable gas cooler feed pipe 41. The entrained steam condensate discharge port 1001 is connected to the entrained steam condensate inlet 45 on the circulation pipe 8 through the entrained steam condensate pipe 40, which is used to discharge the entrained steam condensate into the evaporator for re-evaporation and purification. The entrained steam condensate is discharged into the circulation pipe 8 for re-evaporation, which can solve the problem of high impurity gas content of the distillate and improve the quality of the distillate. The non-condensable gas cooler 12 is used for further cooling and dehumidification of the non-condensable gas, and its outlet is connected to the radioactive ventilation system through the non-condensable gas discharge pipe 42.

[0056] The non-condensable gas recovery and treatment unit also includes supporting pipelines.

[0057] Preferably, the distillate recovery and utilization unit comprises: a distillate receiving tank 6, a distillate pump 7, and a distillate heat exchanger 9. The distillate heat exchanger 9 is used to recycle the heat of the distillate to preheat the waste liquid and to collect the distillate condensed from the steam in the shell side of the heating chamber 3. The distillate receiving tank 6 is provided with a distillate receiving port 57 at the top, and the distillate receiving port 57 is connected to the distillate outlet 304 on the shell side of the heating chamber 3 through a distillate collecting pipe 24. The distillate receiving tank 6 is also provided with a distillate receiving tank pressure balance port 58 at the top. The shell side of the heating chamber 3 is provided with a non-condensable gas flow outlet 305 and a pressure balance port 308, and the bottom is provided with a distillate outlet 304. The distillate receiving tank pressure balance port 58 is connected to the pressure balance port 308 on the upper shell side of the heating chamber 3 through a distillate receiving tank pressure balance pipe 56 to ensure that the distillate receiving tank 6 forms a certain pressure so that the distillate flows out smoothly. The lower end outlet of the distillate receiving tank 6 is connected to the distillate pump 7 through a distillate pump inlet pipe 25.

[0058] The pipeline connected at the outlet of the distillate pump 7 branches into a distillate waste heat recovery pipeline 27 and a distillate total recycling pipeline 26. The distillate total recycling pipeline 26 is further branched into a superheated water pipeline 51, a distillate reflux pipeline 52, and a distillate total reflux pipeline 55. The distillate waste heat recovery pipeline 27 is connected to the shell side inlet of the distillate heat exchanger 9, the superheated water pipeline 51 is connected to the superheated water inlet 50 at the outlet compression secondary steam pipeline 22 of the compressor 4, the distillate reflux pipeline 52 is connected to the distillate partial reflux inlet 102 at the top of the purification chamber 1, and the distillate total reflux pipeline 55 is connected to the upper total reflux inlet 203 of the separation chamber 2. Furthermore, the tube side inlet end of the distillate heat exchanger 9 is connected to the waste liquid feeding pipeline 31, and the waste liquid feeding pipeline 31 is provided with a waste liquid feeding regulating valve 32. The tube side outlet end of the distillate heat exchanger 9 is connected to the upper waste liquid inlet on the shell side of the non-condensable gas heat exchanger 10 via the heat exchanger connecting pipeline 33, and the shell side outlet of the distillate heat exchanger 9 is discharged from the system via the distillate discharge pipeline 28.

[0059] The distillate recovery and utilization unit also includes supporting pipelines.

[0060] Preferably, the outlet of the distillate pump 7 is also connected to the pipeline between the outlet of the compressor 4 and the compressed secondary steam inlet 306, the outlet of the distillate pump 7 is also connected to the partial reflux inlet 102 of the distillate at the top of the purification chamber 1, and the outlet of the distillate pump 7 is also connected to the full reflux inlet 203 of the distillate at the top of the separation chamber 2.

[0061] Preferably, the heating evaporation unit further comprises: a pressure regulating valve and a pressure sensor arranged at the top of the steam generator 5, the pressure regulating valve and the pressure sensor are connected to form a steam generator pressure regulating control loop 505 for regulating the generated steam pressure, and the steam generator 5 is arranged at a preset distance higher than the separation chamber 2.

[0062] Preferably, the heating evaporation unit further comprises: a differential pressure density meter 15 and a differential pressure level meter 14 arranged in the separation chamber 2 and located at the lower part of the separation chamber 2, the upper and lower ends of the differential pressure density meter 15 are located below the liquid level of the concentrated liquid in the separation chamber 2, and the height difference is fixedly installed, and the differential pressure density meter 15 and the differential pressure level meter 14 are installed close to the inner wall of the separation chamber 2 to avoid the presence of a dead zone; the differential pressure level meter 14 is used to receive the transmission density value of the differential pressure density meter 15, and to feedback the accurate liquid level value according to the relationship between the pressure difference and the liquid level. According to the relationship pressure difference = density × height × gravity acceleration, the pressure difference monitoring value can be monitored online to infer the density of the concentrated liquid, and the degree of concentration of the concentrated liquid during the evaporation operation of the monitoring system can be monitored. By receiving the concentrated liquid density value provided by the differential pressure density meter 15, according to the relationship pressure difference = density × height × gravity acceleration, the liquid level of the concentrated liquid in the separation chamber 2 can be measured online, which is used to control the liquid level of the concentrated liquid in the separation chamber 2 during the operation of the system.

[0063] Preferably, the upper part of the separation chamber 2 is directly connected to the lower part of the purification chamber 1, and the separation chamber 2 and the purification chamber 1 are an integrated structure. After the secondary steam is initially separated in the separation chamber 2, it flows directly upward into the purification chamber 1 for deep purification operation. In the conventional split structure of the separation chamber 2 and the purification chamber 1, the secondary steam is exchanged for mass transfer in the purification chamber 1, and there is often residual concentrated liquid in the purification chamber 1, which requires a special pipeline to be set up to discharge into the separation chamber 2 for regular sampling and analysis. In the integrated structure, the liquid phase in the purification chamber 1 directly flows into the separation chamber 2 for re-evaporation and concentration treatment, which makes the device structure simpler and more convenient to operate.

[0064] Preferably, the operating pressure of the evaporator is 60 kPaA-85 kPaA, and the operating temperature is 86°C-95°C.

[0065] Preferably, the purification chamber 1 comprises, from bottom to top, a baffle demister 103, a deep purification zone 13, and a wire mesh demister 104, and the deep purification zone 13 is a multi-layer tower plate structure or a packing structure.

[0066] The baffle demister 103 is used to perform preliminary demisting and purification on the secondary steam in the separation chamber 2, and stabilize the airflow pattern of the secondary steam entering the deep purification zone 13; the deep purification zone 13 is used to perform mass transfer exchange on the radioactive droplets entrained in the secondary steam, and recover the key components in the entrained droplets; the wire mesh demister 104 further demists the secondary steam to improve the purification effect of the secondary steam.

[0067] Preferably, the waste liquid first passes through the distillate heat exchanger 9 to recover the heat of the discharged distillate, and then passes through the non-condensable gas heat exchanger 10 to recover the heat of the non-condensable gas flow.

[0068] Preferably, the non-condensable gas heat exchanger 10 is a vertical structure, and the non-condensable gas flow hot fluid and the radioactive waste liquid cold fluid in the non-condensable gas heat exchanger 10 adopt countercurrent heat exchange, and the non-condensable gas flow enters from the non-condensable gas flow inlet 1002 of the tube side heat exchanger at the bottom of the non-condensable gas heat exchanger 10. The non-condensable gas flow flows upward in the heat exchange tube of the non-condensable gas heat exchanger 10, and the condensate formed by the entrained secondary steam continuously releasing heat can flow downward along the inner wall of the heat exchange tube of the non-condensable gas heat exchanger 10 to the lower part of the non-condensable gas heat exchanger 10 for collection. More importantly, the entrained steam condensate can be heated and heated by the high-temperature non-condensable gas flow during the process of flowing downward along the inner wall of the heat exchange tube of the non-condensable gas heat exchanger 10, which can reduce the amount of impurity gas dissolved in the condensate and maximize the discharge amount of impurity gas in the system.

[0069] The radioactive liquid waste negative pressure heat pump evaporation treatment system in this embodiment is an external heating type radioactive liquid waste negative pressure heat pump evaporation treatment system.

[0070] The operation process of establishing a stable production state in this example system is as follows:

[0071] (1) The steam generator 5 is filled with radioactive waste liquid to a set liquid level, and the steam generator 5 is started to heat the radioactive waste liquid to generate heating steam;

[0072] (2) Open the heating steam regulating valve 38, and pass the heating steam through the heating steam pipeline 37, through the start-up heating steam inlet 303 at the lower part of the heat exchange tube side of the heating chamber 3, and into the heat exchange tube 307 of the heating chamber, so as to directly contact with the waste liquid in the heat exchange tube 307 of the heating chamber. The waste liquid in the heat exchange tube 307 of the heating chamber is heated and gradually vaporized, forming a cold and hot density difference with the cold radioactive waste liquid in the circulation tube 8, thereby generating a thermal siphon effect, and the radioactive waste liquid establishes a circulating flow in the natural circulation loop;

[0073] (3) As the temperature of the radioactive waste liquid gradually increases, the vapor phase fraction of the vapor-liquid two-phase flow in the circulation pipe 8 gradually increases, and the natural circulation driving force formed by the density difference also gradually increases, thereby gradually accelerating the circulation speed of the radioactive waste liquid;

[0074] (4) When the temperature of the waste liquid approaches the saturation temperature, the compressor 4 is slowly started to suck the air in the evaporator to form a negative pressure of about 70 kPaA, and the waste liquid is flashed to produce secondary steam; the secondary steam is initially separated into vapor and liquid in the separation chamber 2, and then deeply removed from the mist and foam in the purification chamber 1, and then enters the compressor 4 to be compressed into high-temperature and high-pressure steam, and then enters the shell side of the heating chamber 3 to heat the waste liquid;

[0075] (5) As the amount of secondary steam gradually increases, the heating power of the steam generator 5 and the opening of the heating steam regulating valve 38 are continuously reduced until the introduction of heating steam is completely stopped.

[0076] (6) The operating pressure of the separation chamber 2 is controlled to be stable, and the secondary steam on the shell side of the heating chamber 3 releases heat and condenses into distillate. The quality of the distillate at this stage is not up to standard and cannot be discharged. It is fully refluxed to the evaporator through the distillate collection pipeline 24, the distillate receiving tank 6, the distillate pump 7, the distillate total recycling pipeline 26, and the distillate full reflux pipeline 55;

[0077] (7) After the quality of the distillate reaches the standard, the system operation is stable and can be transferred to normal production status.

[0078] Through the above process, the system can quickly establish a stable production state.

[0079] During the operation of the system in this example, the startup steam is passed into the heat exchange tube 307 in the heating chamber, which can push the waste liquid upward, thereby inducing natural circulation; the startup steam directly contacts the heated waste liquid, and has high heat transfer efficiency; it can promote the flow and mixing of cold and hot waste liquids between the heating chamber and the separation chamber, thereby accelerating the preheating process; the startup process has a strong operational independence and does not generate additional waste liquid or waste gas; after heating the waste liquid, the startup steam flows through the separation chamber 2 and the purification chamber 1 to remove the mist and foam entrainment, and then enters the shell side of the heating chamber 3 to condense into distillate. The distillate has a high quality, so the whole process time can be shortened, the startup operation can be further accelerated, and the system can establish a stable production state as soon as possible.

[0080] During the normal operation stage of the system, the radioactive waste liquid enters the tube side of the distillate heat exchanger 9 through the waste liquid feeding pipe 31 at a certain flow rate, recovers the heat of the distillate on the shell side of the distillate heat exchanger 9, and the waste liquid is preheated to about 60°C. The waste liquid then enters the shell side of the non-condensable gas heat exchanger 10 through the heat exchanger connecting pipe 33, absorbs the heat of the non-condensable gas flow on the tube side of the non-condensable gas heat exchanger 10, and is heated to about 90°C. It is then merged into the circulating concentrated liquid in the circulating pipe 8 through the steam generator feed pipe 34, the steam generator 5, and the steam generator discharge pipe 36. The concentrated liquid in the heat exchange tube 307 of the heating chamber flows upward along the heat exchange tube 307 of the heating chamber under the thrust of natural circulation, and is heated by the steam on the shell side of the heating chamber 3, and partially vaporizes to produce secondary steam, with a vaporization rate of about 0.03; the concentrated liquid and secondary steam in the heat exchange tube 307 of the heating chamber enter the separation chamber 2 through the waste liquid circulation inlet 202 of the separation chamber, and gas-liquid separation is carried out in the separation chamber 2. The operating pressure in the separation chamber 2 is about 70kPaA, and the liquid phase concentrated liquid obtained by separation enters the heat exchange tube 307 of the heating chamber through the circulation pipe 8 and is heated and evaporated again. The secondary steam obtained by separation enters the purification chamber 1, and in the purification chamber 1, the secondary steam airflow moves upward, and is firstly removed by the baffle demister 103 to remove the entrained droplets, and the airflow pattern is stabilized, and then flows through the deep purification area 13 in the purification chamber 1, and performs deep mass transfer exchange with the reflux distillate, so that the secondary steam airflow is purified, and finally the secondary steam flows through the wire mesh demister 104 to further remove the entrained droplets. The purified secondary steam enters the compressor 4 through the evaporation secondary steam pipeline 21, is pressurized and heated to about 105°C, and then enters the shell side of the heating chamber 3 through the compression secondary steam pipeline 22 to condense and release heat to form distillate, which provides heat for the evaporation of the circulating concentrated liquid in the heating chamber heat exchange tube 307. The non-condensable gas and uncondensed secondary steam on the shell side of the heating chamber 3 constitute a non-condensable gas flow, which enters the non-condensable gas recovery and treatment unit through the non-condensable gas flow pipeline 39; the distillate on the shell side of the heating chamber 3 is discharged through the lower distillate outlet 304, and enters the distillate recovery and utilization unit through the distillate collection pipeline 24.

[0081] In the non-condensable gas recovery and treatment unit, the non-condensable gas flow flows upward on the tube side of the non-condensable gas heat exchanger 10, the secondary steam in the non-condensable gas flow releases heat and condenses, and the resulting condensate flows downward along the inner wall of the tube under the action of gravity, and is discharged through the entrained steam condensate discharge port 1001, and discharged to the circulation pipe 8 through the steam condensate pipe 40 for re-evaporation and purification; to prevent cross-contamination, the lower end of the non-condensable gas heat exchanger 10 is arranged to be higher than the preset distance of the separation chamber 2, specifically higher than 2m, and a U-shaped bend is set on the entrained steam condensate pipe 40 to form a liquid seal to prevent cross-contamination between the non-condensable gas heat exchanger 10 and the evaporator. The non-condensable gas flow treated by the non-condensable gas heat exchanger 10 still has a high temperature and humidity, and is discharged from the non-condensable gas cooler feed pipe 41 to the non-condensable gas cooler 12 for further cooling and dehumidification. The non-condensable gas flow after cooling and dehumidification by the non-condensable gas cooler 12 enters the downstream radioactive ventilation system through the non-condensable gas discharge pipe 42.

[0082] In the distillate recovery and utilization unit, the distillate is collected by the distillate receiving tank 6, and then enters the distillate pump 7 through the distillate pump inlet pipe 25 to be transported. A part of the distillate is reused through the distillate total recycling pipe 26. The recycled distillate is divided into two branches. Most of the recycled distillate enters the distillate reflux liquid inlet 102 at the top of the purification chamber 1 through the distillate reflux pipe 52 for reflux operation, and the reflux ratio is selected to be about 0.3; a small part of the recycled distillate passes through the desuperheated water pipe 51 and is used as desuperheated water for compressed steam at the outlet of the compressor 4; the remaining distillate enters the shell side of the distillate heat exchanger 9 through the distillate waste heat recovery pipe 27 to preheat the waste liquid to be treated on the tube side of the distillate heat exchanger 9, and the distillate after heat exchange enters the outside of the system through the distillate discharge pipe 28 for collection or discharge.

[0083] Furthermore, the principle and beneficial effects of the method for quickly establishing a stable production state of the system are described as follows:

[0084] a) Passing steam into the heat exchange tubes in the heating chamber 3 can push the waste liquid upward along the heat exchange tubes, causing a circulation flow;

[0085] b) The waste liquid is heated by direct contact with steam, which has high heat transfer efficiency and can provide a large driving force for the circulation of the waste liquid, so as to promote the uniform mixing of the cold and hot waste liquids between the separation chamber 2 and the heating chamber 3, accelerate the system preheating process, and shorten the time to establish a stable production state;

[0086] c) Using waste liquid as steam-generating medium to directly generate steam, without the need for a desalted water system or compressed air system, simplifies the system, enhances the independence of system operation, and does not generate additional waste liquid or waste gas;

[0087] d) Startup steam is introduced into the heat exchange tube side of the heating chamber 3. The startup steam directly enters the evaporator and flows through the separation chamber 3 and the purification chamber 1 to remove the mist and foam entrainment. The obtained distillate is of high quality. Therefore, the quality of the distillate produced during the startup process of this system can meet the standards quickly, the full reflux time is short, and the time to establish a stable production state is further shortened.

[0088] The beneficial effects of the negative pressure heat pump evaporation treatment system for radioactive waste liquid described in this embodiment are summarized as follows:

[0089] a) The system is simple, independent, and has higher separation efficiency, which improves product quality;

[0090] b) No secondary waste liquid or secondary waste gas is generated during the treatment process, which greatly increases the energy-saving and emission-reduction effect of the system;

[0091] c) It can quickly establish a stable production state, which is conducive to the emergency treatment of radioactive waste liquid in sudden or emergency situations of nuclear power plants;

[0092] d) It can easily and reliably process and recycle non-condensable gases, effectively improve energy utilization, and protect the service life of subsequent systems.

[0093] It is to be understood that the above embodiments are merely exemplary embodiments used to illustrate the principles of the present invention, but the present invention is not limited thereto. For those of ordinary skill in the art, various modifications and improvements can be made without departing from the spirit and essence of the present invention, and these modifications and improvements are also considered to be within the scope of protection of the present invention.

Claims

1. A radioactive waste liquid negative pressure heat pump evaporation treatment system, characterized in that: include: The heating evaporation unit is used to evaporate the radioactive waste liquid. The heating evaporation unit includes: The steam generator (5) is used to heat the radioactive waste liquid to generate heating steam. The steam generator (5) is provided with a steam generator waste liquid inlet (503) at the top for introducing the radioactive waste liquid. The steam generator waste liquid outlet (502) at the bottom is connected to the circulation pipe (8). The steam generator (5) is also provided with a heating steam outlet (501) at the top for connecting to the start-up heating steam inlet (303) at the bottom of the tube side of the heating chamber (3). The evaporator comprises: a heating chamber (3), a separation chamber (2), a purification chamber (1), and a circulation pipe (8); a heating chamber waste liquid circulation outlet (302) on the upper end tube side of the heating chamber (3) is connected to a separation chamber waste liquid circulation inlet (202) of the separation chamber (2); the upper part of the separation chamber (2) is connected to the lower part of the purification chamber (1); a heating chamber waste liquid circulation inlet (301) on the lower part of the tube side of the heating chamber (3) and a separation chamber waste liquid circulation outlet (201) on the lower part of the separation chamber (2) are connected via the circulation pipe (8); a startup heating steam inlet (303) on the tube side of the heating chamber (3) is connected to a heating steam outlet (501) of a steam generator (5); and the heating steam generated in the steam generator (5) is introduced into the tube side of the heating chamber (3) to heat the radioactive waste liquid in the tube side; A non-condensable gas recovery and treatment unit is used for recovering and treating the non-condensable gas, and a shell-side non-condensable gas flow outlet (305) of the heating chamber (3) is connected to the non-condensable gas recovery and treatment unit; A compressor (4), wherein the inlet of the compressor (4) is connected to the secondary steam outlet (101) at the top of the purification chamber (1), and the outlet of the compressor (4) is connected to the compressed secondary steam inlet (306) at the shell side of the heating chamber (3); The negative pressure heat pump evaporation treatment system for radioactive waste liquid also includes: A distillate recovery and utilization unit is used for distillate recovery and utilization, and the shell side distillate outlet (304) of the heating chamber (3) is connected to the distillate recovery and utilization unit; The distillate recovery and utilization unit comprises: a distillate receiving tank (6), a distillate pump (7), and a distillate heat exchanger (9). The upper portion of the distillate receiving tank (6) is provided with a distillate receiving port (57), which is connected to a distillate outlet (304) on the shell side of a heating chamber (3). The upper portion of the distillate receiving tank (6) is also provided with a distillate receiving tank pressure balance port (58), which is connected to a pressure balance port (308) on the upper portion of the shell side of the heating chamber (3). The lower end outlet of the distillate receiving tank (6) is connected to the distillate pump (7), the outlet of the distillate pump (7) is connected to a shell side inlet of the distillate heat exchanger (9), the tube side inlet of the distillate heat exchanger (9) is used to input radioactive waste liquid, and the tube side outlet of the distillate heat exchanger (9) is connected to a non-condensable gas recovery and treatment unit.

2. The radioactive waste liquid negative pressure heat pump evaporation treatment system according to claim 1 is characterized in that: The non-condensable gas recovery and treatment unit comprises: a non-condensable gas heat exchanger (10) and a non-condensable gas cooler (12), which respectively recover waste heat and cool and dehumidify the non-condensable gas flow of the system; a waste liquid inlet (503) of the steam generator is connected to the shell side outlet of the non-condensable gas heat exchanger (10); the shell side inlet of the non-condensable gas heat exchanger (10) is used to introduce radioactive waste liquid; a shell side non-condensable gas flow outlet (305) of the heating chamber (3) is connected to a non-condensable gas flow inlet (1002) of the heat exchanger on the lower tube side of the non-condensable gas heat exchanger (10); a heat exchanger non-condensable gas flow outlet (1003) is provided on the upper tube side of the non-condensable gas heat exchanger; the heat exchanger non-condensable gas flow outlet (1003) is connected to the non-condensable gas cooler (12); and a steam condensate discharge outlet (1001) is provided at the bottom of the non-condensable gas heat exchanger (10) and is connected to a circulation pipe (8).

3. The radioactive waste liquid negative pressure heat pump evaporation treatment system according to claim 1, characterized in that: The outlet of the distillate pump (7) is also connected to the pipeline between the outlet of the compressor (4) and the compressed secondary steam inlet (306), the outlet of the distillate pump (7) is also connected to the partial reflux inlet (102) of the distillate at the top of the purification chamber (1), and the outlet of the distillate pump (7) is also connected to the full reflux inlet (203) of the distillate at the top of the separation chamber (2).

4. The radioactive waste liquid negative pressure heat pump evaporation treatment system according to any one of claims 1 to 3, characterized in that: The heating evaporation unit also includes: a pressure regulating valve and a pressure sensor arranged on the top of the steam generator (5); the pressure regulating valve and the pressure sensor are connected to form a regulating loop.

5. The radioactive waste liquid negative pressure heat pump evaporation treatment system according to any one of claims 1 to 3, characterized in that: The heating evaporation unit further comprises: a differential pressure density meter (15) and a differential pressure level meter (14) arranged in the separation chamber (2); the upper and lower ends of the differential pressure density meter (15) are located below the liquid level of the concentrated liquid in the separation chamber (2) and are installed close to the inner wall of the separation chamber (2); the differential pressure level meter (14) is used to receive the transmission density value of the differential pressure density meter (15) and to feed back an accurate liquid level value according to the relationship between the pressure difference and the liquid level.

6. The radioactive waste liquid negative pressure heat pump evaporation treatment system according to any one of claims 1 to 3, characterized in that: The upper part of the separation chamber (2) is connected to the lower part of the purification chamber (1), and the separation chamber (2) and the purification chamber (1) are an integrated structure.

7. The radioactive waste liquid negative pressure heat pump evaporation treatment system according to any one of claims 1 to 3, characterized in that: The purification chamber (1) comprises, from bottom to top, a baffle demister (103), a deep purification zone (13), and a wire mesh demister (104); the deep purification zone (13) is a multi-layer tower plate structure or a packing structure.

8. The radioactive waste liquid negative pressure heat pump evaporation treatment system according to any one of claims 2 to 3, characterized in that: The non-condensable gas heat exchanger (10) is a vertical structure. The non-condensable gas flow hot fluid and the radioactive waste liquid cold fluid in the non-condensable gas heat exchanger (10) adopt countercurrent heat exchange. The non-condensable gas flow enters the non-condensable gas heat exchanger (10) through the non-condensable gas flow inlet (1002) of the lower tube side heat exchanger.

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