A supercritical water oxidation system and method suitable for radioactive waste treatment

Abstract

The application discloses a supercritical water oxidation system and method suitable for radioactive waste treatment, which comprises a radioactive material pretreatment unit, an oxygen multi-stage supply unit, a pure water supply unit, a reactor unit and a deep treatment unit, can realize efficient and complete degradation of organic matter after supercritical water oxidation of radioactive waste, and complete solidification of nuclides. The supercritical water oxidation system has the functions of low-temperature material injection, multi-stage feeding and multi-stage oxygen supply, mechanical devices such as scrapers and filter walls are arranged in the reactor to realize efficient separation of radioactive nuclide salt and supercritical water, so that most of the nuclide salt is solidified and treated; the gas phase and the liquid phase after reaction are treated by a conventional deep treatment unit and discharged up to the standard, and the solid-phase nuclide salt is safely transported and treated after shielding. The supercritical water oxidation system disclosed by the application has universality for radioactive organic waste and can be widely applied to the field of inorganic reduction treatment of radioactive waste.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of hazardous waste treatment, and relates to a supercritical water oxidation system and method suitable for radioactive waste treatment. BACKGROUND

[0002] With the development of nuclear energy represented by nuclear power and the utilization of nuclear technology, a large amount of radioactive waste is generated in the operation and decommissioning process of nuclear power plants. Radioactive waste is divided into high-level radioactive waste, medium-level radioactive waste and low-level radioactive waste according to its radioactivity, but it basically contains radioactive nuclides such as U, 235 U、 239 Pu、 137 Cs、 90 Sr、 60 Co, etc. Due to the physical and chemical properties of radioactive waste such as flammability, explosiveness and radioactivity, there is currently no safe and effective treatment process, and it is temporarily stored in nuclear facilities for treatment.

[0003] At present, the mainstream treatment process for radioactive waste is cement solidification, which occupies limited waste storage space and increases the final disposal cost. The existing incineration, steam reforming and glass solidification technologies have a series of engineering technical application difficulties and pain points such as complex industrial process, generation of secondary pollution such as NO X 、SO X 、PM2.5, dioxin and radioactive fly ash, operation stability and maintenance, and urgently need a green, efficient, complete, environmentally friendly and economic treatment technology.

[0004] Compared with the existing radioactive waste volume reduction treatment technology (incineration method, glass solidification, etc.), the supercritical water oxidation technology has the following significant technical advantages: 1) the reaction is rapid and complete, and the removal rate of organic pollutants is as high as 99% or more; 2) the temperature is moderate, there is no secondary pollution such as dioxin and radioactive fly ash, and the gas phase can be discharged up to standard; 3) the solubility of nuclides in supercritical water is extremely low, so that efficient solid-phase conversion and separation of nuclides can be realized; 4) the system is simple and has high automation. SUMMARY

[0005] The application aims at solving the problems of the conventional radioactive waste treatment technology, such as the generation of secondary waste liquid, the incomplete solidification or too large capacity of nuclides, and provides a supercritical water oxidation system and method suitable for radioactive waste treatment.

[0006] To achieve the above-mentioned purpose, the application adopts the following technical solutions:

[0007] A supercritical water oxidation system suitable for radioactive waste treatment comprises a reaction unit, wherein a supercritical water inlet, a first-stage oxidant inlet, a first-stage material inlet, a second-stage material inlet, a second-stage oxidant inlet, a third-stage oxidant inlet and a reaction outlet are arranged on the reaction unit; the supercritical water inlet is connected with a pure water supply unit, the first-stage oxidant inlet, the second-stage oxidant inlet and the third-stage oxidant inlet are connected with an oxygen multi-stage supply unit, and the first-stage material inlet and the second-stage material inlet are connected with a radioactive material supply unit; and the reaction outlet is connected with a deep treatment unit.

[0008] The system is further improved in that:

[0009] The radioactive material supply unit comprises a material deployment tank, the outlet of the material deployment tank is connected with a material buffer tank, a material pump and a material preheater in sequence, and the outlet of the material preheater is connected with the first-stage material inlet and the second-stage material inlet.

[0010] An accident tank is further connected with the reactor, and the outlet of the accident tank is connected with the material deployment tank.

[0011] A pressure gauge is arranged on the pipeline between the material pump and the material preheater, a pipeline is led out from the material preheater to the material buffer tank through a valve.

[0012] An additive storage tank is arranged on the pipeline between the material buffer tank and the material pump, and the additives in the additive tank 10 include pH adjusters, catalysts, pre-precipitation agents and co-oxidants.

[0013] The oxygen multi-stage supply unit comprises a liquid oxygen storage tank, a liquid oxygen pump, a liquid oxygen vaporizer and an oxygen buffer tank connected in sequence, and the outlet of the oxygen buffer tank is connected with the first-stage oxidant inlet, the second-stage oxidant inlet and the third-stage oxidant inlet.

[0014] The pure water supply unit comprises a pure water tank, a pure water high-pressure pump and a heater connected in sequence, and the outlet of the heater is connected to the supercritical water inlet.

[0015] The reactor comprises a cylinder body and a cover body, and the interior comprises an upper oxidation chamber and a lower salt discharge chamber.

[0016] The advanced treatment unit comprises an expander and a pressure reducer; the outlet of the salt discharge chamber at the bottom of the reactor cylinder body is connected to the expander, the outlet of the expander is connected to a shielded transport box, the reaction outlet on the reactor cover body is connected to the pressure reducer, the outlet of the pressure reducer is connected to a water quality analyzer and a gas-liquid separator in sequence, the gas phase outlet of the gas-liquid separator is connected to a gas phase processor, and the liquid phase outlet is connected to a liquid phase processor.

[0017] A supercritical water oxidation method suitable for radioactive waste treatment comprises the following steps:

[0018] When the system is running, the reactor is kept at 27MPa and 600 DEG C steady state, at this time, liquid oxygen at the liquid oxygen pump inlet is pressurized to the rated pressure by the liquid oxygen pump and then passes through the liquid oxygen vaporizer, and then the oxygen gas buffer tank outlet is divided into three branches and connected to the first-stage oxidant inlet, the second-stage oxidant inlet and the third-stage oxidant inlet of the reaction respectively; the material is pressurized by the material pump and then enters from the first-stage material inlet and the second-stage material inlet after being preheated in the reactor interior; the supercritical water oxidation reaction of oxygen and material occurs in the oxidation zone of the reactor interior, the reaction water enters the water quality analyzer for detection, and if qualified, enters the gas-liquid separator, the gas phase passes through the gas phase processor and is discharged after reaching the standard, and the liquid phase is discharged after reaching the standard through the liquid phase processor; the nuclide salt in the reaction product is discharged through the salt discharge port at the lower part of the reactor into the expander and the shielded transport box, and waits for subsequent solidification operation.

[0019] Compared with the prior art, the present application has the following beneficial effects:

[0020] 1. On-line nuclide solidification and efficient removal. The reactor interior is provided with a scraper and a baffle, etc., which can mechanically remove the nuclides, and because the solubility of the nuclides in supercritical water is extremely low, the nuclides can be safely transported after being discharged from the reactor outlet into the expander and the shielded transport box to realize subsequent solidification operation.

[0021] 2. Efficient removal of radioactive waste. By arranging multiple-stage material inlets and oxidant inlets on the reactor cover body and the cylinder body, the reaction efficiency can be improved, and the organic matter and the oxidant can be fully reacted, especially the third-stage oxidant inlet is arranged at the lower part of the reactor, which can make the residual organic matter fully react.

[0022] 3. Water quality monitoring. By setting water quality analyzer, the organic matter concentration of reaction effluent can be monitored, if not up to standard, re-enter the material blending tank, and then supercritical water oxidation reaction is carried out again; if up to standard, enter the subsequent gas-liquid separator and waste liquid collection tank, and then solidification operation is carried out accordingly. BRIEF DESCRIPTION OF DRAWINGS

[0023] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiments. It should be understood that the following drawings only show some embodiments of the present application, and therefore should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can also be obtained without creative labor on the basis of these drawings.

[0024] Figure 1 It is a schematic diagram of the overall structure of the present application.

[0025] Among them, 1-pure water tank; 2-pure water high-pressure pump; 3-heater; 4-liquid oxygen storage tank; 5-liquid oxygen pump; 6-liquid oxygen vaporizer; 7-oxygen buffer tank; 8-material blending tank; 9-material buffer tank; 10-additive storage tank; 11-material pump; 12-pressure gauge; 13-material preheater; 14-gas phase processor; 15-gas-liquid separator; 16-water quality analyzer; 17-pressure reducer; 18-expander; 19-shielded transport box; 20-reactor; 21-accident tank; 22-liquid phase processor; N1-supercritical water inlet; N2-primary oxidant inlet; N3-primary material inlet; N4-secondary material inlet; N5-secondary oxidant inlet; N6-tertiary oxidant inlet; N7-reaction effluent outlet. DETAILED DESCRIPTION

[0026] In order to make the purpose, technical solutions and advantages of the embodiments of the present application more clear, the following will combine the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all the embodiments. The components of the embodiments of the present application described and shown in the drawings can be arranged and designed in various different configurations.

[0027] Therefore, the following detailed description of the embodiments of the present application provided in the drawings is not intended to limit the scope of the claimed application, but only represents selected embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0028] It should be noted that: similar numbers and letters represent similar items in the following drawings, therefore, once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings.

[0029] In the description of the embodiments of the present application, it should be noted that if the terms "upper", "lower", "horizontal", "inner" and the like indicating the orientation or position relationship are based on the orientation or position relationship shown in the drawings, or the orientation or position relationship of the product of the present application when it is usually placed, which is only for the convenience of describing the present application and simplifying the description, and does not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application. In addition, the terms "first", "second" and the like are only used to distinguish the description and cannot be understood as indicating or implying relative importance.

[0030] In addition, if the term "horizontal" appears, it does not mean that the component must be absolutely horizontal, but can be slightly inclined. For example, "horizontal" only means that its direction is relatively more horizontal than "vertical", and does not mean that the structure must be completely horizontal, but can be slightly inclined.

[0031] In the description of the embodiments of the present application, it should be noted that unless otherwise explicitly specified and limited, if the terms "arrangement", "installation", "connection", "connection" appear, they should be understood in a broad sense, for example, they can be fixedly connected, or can be detachably connected, or integrally connected; can be mechanically connected, or can be electrically connected; can be directly connected, or can be indirectly connected through an intermediate medium; can be the communication inside two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0032] The present application will be described in further detail below in conjunction with the accompanying drawings:

[0033] Referring to Figure 1 The embodiment of the present application discloses a supercritical water oxidation system suitable for radioactive waste treatment, mainly including a reaction unit, a radioactive material supply unit, an oxygen multi-stage supply unit, a pure water supply unit, a residual heat cascade utilization unit, a safety emergency treatment unit and a deep treatment unit.

[0034] The reaction unit includes a reactor 20, a first oxidant inlet N2, a first material inlet N3, a second oxidant inlet N5, a second material inlet N4, a third oxidant inlet N6 and a supercritical water inlet N1, and performs supercritical water oxidation reaction of radioactive waste;

[0035] The radioactive material supply unit includes a material preparation tank 8, a material buffer tank 9, a material pump 11, a pressure gauge 12, and a valve, through which the material enters a material preheating pipeline in the reactor, and is divided into two branches at the outlet of the material preheating pipeline and connected with a first material inlet N3 and a second material inlet N4 of the reactor, respectively. The radioactive material includes but is not limited to radioactive waste resin, radioactive waste TBP solvent, radioactive waste engine oil and lubricating oil, radioactive waste plastic and other radioactive organic materials. The radioactive material of the material supply unit is not directly heated by a heater, but is low-temperature sprayed into the reactor 20 after passing through the material preheater and mixed with high-temperature supercritical water to occur supercritical water oxidation reaction. After the radioactive material in the reactor is subjected to supercritical water oxidation reaction, the radionuclide salt is separated from the reacted supercritical fluid by mechanical devices including but not limited to a scraper, a filter wall and the like in the reactor 20. The material supply unit is provided with an auxiliary agent tank 10 to regulate the material fluid, and the auxiliary agent includes but is not limited to pH adjusting, catalytic, pre-precipitation, co-oxidation and other functional additives. After the radioactive material in the reactor is subjected to supercritical water oxidation reaction, the radionuclide salt is separated from the reacted supercritical fluid by mechanical devices including but not limited to a scraper, a filter wall and the like in the reactor 20.

[0036] The oxygen multi-stage supply unit includes a liquid oxygen storage tank 4, a liquid oxygen pump 5, a liquid oxygen vaporizer 6, and an oxygen buffer tank 7. The outlet of the oxygen buffer tank is divided into three branches and connected with a first oxidant inlet N2, a second oxidant inlet N5, and a third oxidant inlet N6 of the reactor 20, respectively. The oxygen supply unit is divided into three stages and enters the reactor, including the first oxidant inlet N2, the second oxidant inlet N5, and the salt discharge chamber oxidant inlet N6.

[0037] The pure water supply unit includes a pure water tank 1, a pure water high-pressure pump 2, a pure water preheater reactor, and a heater 3, which sprays into the reactor 20 and mixes with the preheated material and oxygen;

[0038] The waste heat cascade utilization unit includes a plurality of cooling water circuits arranged in the reactor and a material preheater 13. The waste heat utilization unit includes a material preheating pipeline, a pure water preheating pipeline, a cooling water pipeline, etc., which can be arranged in the reactor 20 or outside the reactor 20.

[0039] The safety emergency treatment unit includes an accident tank 20.

[0040] The deep treatment unit comprises a volume expander 18, a shielding transfer box 19, a water quality analyzer 16, a gas-liquid separator 15, a gas phase processor 14 and a liquid phase processor 22. The reactor 20 is composed of a cylinder and a cover, and comprises an upper oxidation chamber and a lower salt discharge chamber in the interior, and the salt discharge chamber is connected with the external volume expander 18 through a valve. The salt discharge valve can be always opened or intermittently opened. The volume expander 18 is arranged in the reactor unit. After the nuclide salt fluid is discharged into the volume expander through the salt discharge valve, the nuclide salt fluid can be initially depressurized, and then the overheat steam is discharged and the pressure is released through the valve on the volume expander 18. The process used in the gas phase processor 14 includes but is not limited to filtration, adsorption, dilution, storage and the like. The process used in the liquid phase processor 22 includes but is not limited to filtration, adsorption, precipitation, electrodialysis, biological treatment and the like.

[0041] Principles and processes of the present application:

[0042] When the system is running, the reactor 20 is kept at 27 MPa and 600 DEG C steady state. At this time, the liquid oxygen pump 5 inlet is a certain concentration of liquid oxygen, which is pressurized to the rated pressure by the liquid oxygen pump 5, and then passes through the liquid oxygen vaporizer 6. Subsequently, the oxygen buffer tank 7 outlet is divided into three branches, which are connected with the first-stage oxidant inlet N2, the second-stage oxidant inlet N5 and the third-stage oxidant inlet N6 of the reaction, respectively. The material is pressurized by the material pump 11, and then enters from the first-stage material inlet N3 and the second-stage material inlet N4 after being preheated in the interior of the reactor 20. The oxygen and the material are oxidized in the supercritical water oxidation reaction zone in the reactor 20, and the reaction water enters the water quality analyzer 16 for detection. If the water quality is qualified, the water enters the gas-liquid separator 15. The gas phase is treated by the gas phase processor 14 and then discharged after reaching the standard. The liquid phase is treated by the liquid phase processor 22 and then discharged after reaching the standard. The nuclide salt in the reaction product is discharged from the lower salt discharge port of the reactor 20 to the volume expander 18 and the shielding transfer box 19, and waits for subsequent solidification operation. In summary, the system provides a feasible scheme for the disposal of radioactive waste.

[0043] The above only describes the preferred embodiments of the present application and is not used to limit the present application. For those skilled in the art, the present application can have various modifications and changes. Any modification, equivalent replacement, improvement and the like made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A supercritical water oxidation system suitable for use in the treatment of radioactive waste, characterised in that, The reactor (20) is provided with a supercritical water inlet (N1), a primary oxidant inlet (N2), a primary material inlet (N3), a secondary material inlet (N4), a secondary oxidant inlet (N5), a tertiary oxidant inlet (N6) and a reaction water outlet (N7); the supercritical water inlet (N1) is connected with a pure water supply unit, the primary oxidant inlet (N2), the secondary oxidant inlet (N5) and the tertiary oxidant inlet (N6) are connected with an oxygen multi-stage supply unit, the primary material inlet (N3) and the secondary material inlet (N4) are connected with a radioactive material supply unit; the reaction water outlet (N7) is connected with a deep treatment unit. The supercritical water inlet (N1), the primary oxidant inlet (N2), the primary material inlet (N3), the secondary material inlet (N4), the secondary oxidant inlet (N5) and the reaction water outlet (N7) are arranged on the upper part of the reactor, and the tertiary oxidant inlet (N6) is arranged on the lower part of the reactor; the primary oxidant inlet (N2) is below the supercritical water inlet (N1), the primary material inlet (N3) is below the primary oxidant inlet (N2), and the secondary material inlet (N4), the secondary oxidant inlet (N5) and the reaction water outlet (N7) are below the primary material inlet (N3).

2. The supercritical water oxidation system suitable for radioactive waste treatment according to claim 1, characterized in that, The radioactive material supply unit comprises a material deployment tank (8), the outlet of the material deployment tank (8) is connected with a material buffer tank (9), a material pump (11) and a material preheater (13) in sequence, and the outlet of the material preheater (13) is connected with the primary material inlet (N3) and the secondary material inlet (N4) respectively.

3. The supercritical water oxidation system suitable for radioactive waste treatment according to claim 2, characterized in that, The reactor (20) is further connected with an accident tank (21), and the outlet of the accident tank (21) is connected with the material deployment tank (8).

4. The supercritical water oxidation system suitable for radioactive waste treatment according to claim 2, characterized by, A pressure gauge (12) is arranged on the pipeline between the material pump (11) and the material preheater (13), and a pipeline is led out from the pressure gauge (12) to the material buffer tank (9) through a valve and returns to the material buffer tank (9).

5. The supercritical water oxidation system suitable for radioactive waste treatment according to claim 2, characterized in that, An additive storage tank (10) is arranged on the pipeline between the material buffer tank (9) and the material pump (11), and the additives in the additive storage tank (10) comprise a pH regulator, a catalyst, a pre-precipitation agent and a co-oxidant.

6. The supercritical water oxidation system suitable for radioactive waste treatment according to claim 1, characterized by, The oxygen multi-stage supply unit comprises a liquid oxygen storage tank (4), a liquid oxygen pump (5), a liquid oxygen vaporizer (6) and an oxygen buffer tank (7) connected in sequence, and the outlet of the oxygen buffer tank (7) is connected with the primary oxidant inlet (N2), the secondary oxidant inlet (N5) and the tertiary oxidant inlet (N6) respectively.

7. The supercritical water oxidation system suitable for radioactive waste treatment according to claim 1, characterized by, The pure water supply unit comprises a pure water tank (1), a pure water high-pressure pump (2) and a heater (3) connected in sequence, and the outlet of the heater (3) is connected with the supercritical water inlet (N1).

8. The supercritical water oxidation system suitable for radioactive waste treatment according to claim 1, characterized by, The reactor (20) comprises a cylinder body and a cover body, and the inside comprises an upper oxidation chamber and a lower salt discharge chamber.

9. The supercritical water oxidation system suitable for radioactive waste treatment according to claim 8, characterized in that, The deep treatment unit comprises an expander (18) and a pressure reducer (17); the outlet of a salt discharge chamber at the bottom of a cylinder of the reactor (20) is connected with the expander (18), and the outlet of the expander (18) is connected with a shielded transfer box (19); a reaction outlet (N7) on a cover of the reactor (20) is connected with the pressure reducer (17), and the outlet of the pressure reducer (17) is connected with a water quality analyzer (16) and a gas-liquid separator (15) in sequence, the gas phase outlet of the gas-liquid separator (15) is connected with a gas phase processor (14), and the liquid phase outlet is connected with a liquid phase processor (22).

10. A supercritical water oxidation method for radioactive waste treatment using the system according to any one of claims 1 to 9, characterized by, The method comprises the following steps: When the system is running, the reactor (20) is kept at 27 MPa and 600 ℃ in a steady state, at this time, the liquid oxygen at the inlet of the liquid oxygen pump (5) is pressurized to the rated pressure by the liquid oxygen pump (5), and then passes through the liquid oxygen vaporizer (6), and then the outlet of the oxygen buffer tank (7) is divided into three branches, which are respectively connected with the first-stage oxidant inlet (N2), the second-stage oxidant inlet (N5) and the third-stage oxidant inlet (N6) of the reaction; the material is pressurized by the material pump (11), and then enters from the first-stage material inlet (N3) and the second-stage material inlet (N4) after being preheated in the reactor (20); the oxygen and the material occur supercritical water oxidation reaction in the oxidation zone of the reactor (20), the reaction water enters the water quality analyzer (16) for detection, and if qualified, enters the gas-liquid separator (15), the gas phase passes through the gas phase processor (14) and is discharged after reaching the standard, and the liquid phase passes through the liquid phase processor (22) and is discharged after reaching the standard; the nuclide salt in the reaction product is discharged through the salt discharge port at the lower part of the reactor (20) to the expander (18) and the shielded transfer box (19), and waits for subsequent solidification operation.

Images