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

Abstract

The application discloses a supercritical water oxidation reactor and method suitable for radioactive waste treatment, which comprises an end cover area, a reaction area and a salt storage area, and mechanical devices such as a scraper and a stirrer are arranged in the core area of the reaction area. The bottom is a nuclide salt storage area, and is provided with a mechanical stirring device and a third oxidant inlet. The application can realize supercritical water oxidation treatment of radioactive waste, utilizes the small solubility of nuclides in supercritical water to remove the nuclides, and simultaneously removes the nuclides mechanically through the scraper. Meanwhile, due to the existence of the cooling membrane wall, not only the heat of the reaction area can be absorbed to prevent the wall surface from over-temperature, but also the residual heat can be utilized. Meanwhile, a sacrificial thin lining is arranged at the key position of the reactor to ensure that the device minimizes the generation of radioactive waste after decommissioning. The reactor has important application value in the field of supercritical water oxidation treatment of radioactive waste.

Description

TECHNICAL FIELD

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

[0002] Nuclear power as a clean energy has become an important part of the energy structure in China. With the emergence of a large number of nuclear power plants, the amount of radioactive waste is also increasing year by year, mainly including radioactive waste ion exchange resin, radioactive waste oil, radioactive waste solvent, radioactive waste protective clothing and gloves, etc. At present, the main methods for treating these radioactive wastes are incineration, plasma incineration, Fenton oxidation, direct solidification, etc. However, these methods all have various problems. Although incineration can significantly reduce the volume of waste, it will cause secondary pollution such as radioactive fly ash; plasma incineration requires the addition of solidification materials and the tail gas treatment system is complex; Fenton oxidation has mild reaction conditions, but the reaction time is long and the amount of secondary waste liquid is large; direct solidification has a simple process, but the volume is increased greatly.

[0003] Supercritical water oxidation technology is a technology that uses the special properties of supercritical water to make radioactive organic matter and oxidizing agents undergo homogeneous oxidation reaction under the conditions of temperature and pressure exceeding the critical point of water, so as to decompose the radioactive organic matter into CO2, H2O, N2, etc., and convert the radionuclide into inorganic nuclide salt. The nuclide salt has extremely low solubility in supercritical water, so it can be easily separated. SUMMARY

[0004] The present application aims to solve the problems in the prior art and provides a supercritical water oxidation reactor and method suitable for radioactive waste treatment. The present application can realize efficient degradation of radioactive waste, and at the same time, the nuclide is separated by a simple mechanical removal method due to the extremely low solubility of the nuclide in supercritical water, so as to minimize the radioactive waste. The reactor has the functions of low-temperature material injection, alcohol co-oxidation, catalytic oxidation, cold wall protection, and waste heat recovery, which ensures the efficient removal of radioactive organic matter and the solidification and separation of nuclides, thereby providing a feasible solution for the treatment of radioactive waste.

[0005] To achieve the above-mentioned purposes, the present application adopts the following technical solutions:

[0006] A supercritical water oxidation reactor suitable for radioactive waste treatment, comprising:

[0007] An end cap part, the end cap part comprises an end part dosing cylinder and an annular cover plate, the end part dosing cylinder is connected to the inner ring of the annular cover plate, and the bottom of the annular cover plate is sealingly connected with the flow guide adiabatic cylinder; the inner cavity of the end part dosing cylinder is an end cap area;

[0008] A center cylinder, a flow guide heat insulation cylinder is arranged in the center cylinder, an inner cavity of the flow guide heat insulation cylinder is a reaction zone, and the reaction zone is communicated with an end cover zone;

[0009] A cooling wall, a cylinder structure with an open top, is sleeved at a bottom of the flow guide heat insulation cylinder, an inner cavity surrounded by the flow guide heat insulation cylinder and the inner side of the cooling wall is a salt storage zone, and the salt storage zone is communicated with the reaction zone.

[0010] The further improvement of the present application is that:

[0011] The top of the end part of the charging cylinder is provided with a high-temperature supercritical water injection port, a primary oxidizing agent inlet and a primary low-temperature material inlet are arranged on the side wall, the primary oxidizing agent inlet is located above the primary low-temperature material inlet, and the high-temperature supercritical water injection port, the primary oxidizing agent inlet and the primary low-temperature material inlet are communicated with the end cover zone.

[0012] The side surface of the annular cover plate is provided with an end cover cooling water inlet and an end cover cooling water outlet, the end surface of the annular cover plate is provided with a secondary low-temperature material inlet and a secondary oxidizing agent inlet, and the secondary low-temperature material inlet and the secondary oxidizing agent inlet are communicated with the reaction zone.

[0013] The stirrer and the scraper are sequentially arranged in the reaction zone from top to bottom.

[0014] The inner wall of the flow guide heat insulation cylinder is provided with a sacrificial thin lining, a through hole is arranged on the cylinder wall of the flow guide heat insulation cylinder and is communicated with the inner side of the cylinder wall of the center cylinder, and a filter wall is arranged in the through hole.

[0015] The cylinder wall of the center cylinder is provided with a material preheater and a heat removal device, the material preheater and the heat removal device are arranged on the outer side of the flow guide heat insulation cylinder, a reaction water outlet is arranged on the side surface of the center cylinder, and the reaction water outlet is communicated with the reaction zone.

[0016] The side surface of the cooling wall is provided with a cooling wall water inlet, a cooling wall water outlet, a third oxidizing agent inlet and a salt discharge port, the third oxidizing agent inlet and the salt discharge port are communicated with the salt storage zone, the third oxidizing agent inlet is arranged on the side wall of the cooling wall, and the salt discharge port is arranged at the bottom of the cooling wall.

[0017] The filter wall is a filter screen or a sintered metal filter.

[0018] The cylinder wall of the center cylinder is a membrane wall, a coil pipe or a cooling cavity with a flow guide function.

[0019] A supercritical water oxidation method suitable for radioactive waste treatment, comprising the following steps:

[0020] The supercritical water, the primary oxidant and the primary low-temperature material are injected into the end cover area, the secondary oxidant and the secondary low-temperature material are input into the reaction area, and the primary oxidant, the primary low-temperature material, the secondary oxidant and the secondary low-temperature material are mixed and oxidized in the reaction area;

[0021] After the reaction, the supercritical water is cooled and decompressed into steam through the filter wall and is discharged through the reaction water outlet, and the nuclide is deposited in the salt storage area and is discharged through the salt discharge port.

[0022] Compared with the prior art, the present application has the following beneficial effects:

[0023] 1. Effective separation of nuclides. Since the solubility of nuclides in supercritical water is extremely low, the nuclides and supercritical water are separated by mechanical means such as scraping and brushing and porous powder sintered wall, which can effectively remove the nuclides in radioactive waste and prevent their diffusion into the environment. The nuclide removal process in the salt storage area can be intermittent or continuous, making the reactor suitable for different systems.

[0024] 2. High temperature in the center of the reaction area and efficient oxidation. The primary oxidant and the low-temperature material release a large amount of heat after converging and reacting at the outlet, and the secondary oxidant and the secondary material also undergo intense oxidation reaction at this place. The high temperature at this place is conducive to the complete degradation of radioactive waste.

[0025] 3. Waste heat utilization and cold wall protection. The presence of cold wall water not only absorbs the heat generated by the reaction, but also prevents the wall from overheating and being damaged. The heated water can also be used for other purposes. BRIEF DESCRIPTION OF DRAWINGS

[0026] 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.

[0027] Figure 1 The present application is a structural schematic diagram.

[0028] 1-end cover area; 2-stirrer; 3-flow guide adiabatic cylinder; 4-scraping brush; 5-heat removal water heater; 6-material preheater; 7-reaction area; 8-filter wall; 9-sacrificial thin liner; 10-salt storage area; 11-cooling wall; N1-high-temperature supercritical water injection port; N2-primary oxidant inlet; N3-primary low-temperature material inlet; N4-end cover cooling water inlet; N5-secondary low-temperature material inlet; N6-secondary oxidant inlet; N7-end cover cooling water outlet; N8-cold wall water inlet; N9-reaction water outlet; N10-cold wall water outlet; N11-third oxidant inlet; N12-salt discharge port. DETAILED DESCRIPTION

[0029] In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the following will clearly and completely describe the technical solutions in the embodiments of the present application with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some but not all of the embodiments of the present application. Generally, the components of the embodiments of the present application described and shown in the drawings can be arranged and designed in various different configurations.

[0030] 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 present application, but only represents selected embodiments of the present application. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present application without creative work fall within the scope of protection of the present application.

[0031] It should be noted that: similar reference numerals 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.

[0032] In the description of the embodiments of the present application, it should be noted that, if the orientation or position relationship indicated by the terms "upper", "lower", "horizontal", "inner" and the like is based on the orientation or position relationship shown in the drawings, or is the orientation or position relationship when the product of the present application is usually placed, and is only for the convenience of describing the present application and simplifying the description, and therefore cannot be understood as indicating or implying that the indicated device or element must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the present application. In addition, the terms "first", "second" and the like are only used for differentiation and cannot be understood as indicating or implying relative importance.

[0033] 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.

[0034] In the description of the embodiments of the present application, it should also be noted that, unless otherwise explicitly specified and limited, if the terms "arrange", "mount", "connect", "connect" appear, they should be understood in a broad sense, for example, can be fixedly connected, can be detachably connected, or integrally connected; can be mechanically connected, can be electrically connected; can be directly connected, can be indirectly connected through an intermediate medium, or can be the communication inside two elements. For those of ordinary skill in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0035] The application will be further described in detail below with reference to the drawings:

[0036] Referring to Figure 1 The application discloses a supercritical water oxidation reactor suitable for radioactive waste treatment, which mainly comprises an upper end cover area 1, a middle reaction and waste heat utilization area 7 and a lower nuclide salt storage area 10. The end cover area 1 is provided with a high-temperature supercritical water injection port N1, a primary oxidizing agent injection port N2, a primary low-temperature material injection port N3, an end cover cooling water injection port N4, an end cover cooling water outlet port N7, a secondary low-temperature material injection port N5 and a secondary oxidizing agent injection port N6. The outer side of the reaction area 7 is provided with a cold wall water injection port N8, a cold wall water outlet port N10 and a reaction water outlet port N9. The inner side of the reaction area 7 is sequentially provided with a flow guide adiabatic cylinder 3 with a sacrificial thin lining 9, a material preheater 6 and a heat extraction heater 5, wherein the wall of the flow guide adiabatic cylinder 3 is provided with a filter wall 8. The core area of the reaction area 7 is provided with mechanical devices such as a scraping brush 4 and a stirrer 2. The bottom is the nuclide salt storage area 10, which is provided with a mechanical stirring device, a tertiary oxidizing agent injection port N11 and a salt discharge port N12.

[0037] The radioactive material is preheated by the material preheater 6 in the reactor, then enters the core reaction area 7 of the reactor through the primary and secondary injection ports of the upper end cover of the reactor, and undergoes supercritical water oxidation reaction after being mixed by high-temperature supercritical water. The oxidizing agent includes but is not limited to being injected into the reactor in three times, and can be injected into the reactor in multiple times according to the reaction condition. The flow guide adiabatic cylinder 3 in the core area of the reactor is internally provided with a sacrificial thin lining 9, and the thin lining 9 can have a reaction catalysis effect according to different materials. The mechanical devices in the core area of the reactor include but are not limited to the scraping brush 4 and the stirrer 2, which are used to mix the reaction fluid and separate the solid nuclide salt. The filter wall 8 of the flow guide adiabatic cylinder is a filter wall with small pores, which can separate the nuclide salt from the supercritical water, and is not limited to a filter screen, a sintered metal filter and the like. The end cover cold wall water is arranged in the inner part of the upper end cover of the reactor, and the center cylinder wall is provided with cylinder wall cold wall water. The loading form of the cold wall water is not limited to a membrane wall, a coil pipe and a cooling cavity with a flow guide effect. The material preheater 6 can be arranged in the reactor according to the use requirement, or can be arranged outside the reactor. The size of the nuclide storage area 10 at the lower part of the reactor can be set according to the nuclide salt content of the material, intermittent salt discharge, continuous salt discharge and the like. The components such as the flow guide adiabatic cylinder 3, the material preheater 6 and the heat extraction heater 5 in the reactor are all arranged in a detachable manner

[0038] The working process of the application:

[0039] Supercritical water, primary oxidant and low-temperature material are respectively injected from corresponding injection ports, mixed and intensely oxidized in the reaction zone 7, and the secondary oxidant and secondary material also react in the reaction zone 7. After the reaction, the nuclide is separated due to low solubility in supercritical water, the supercritical water is cooled and decompressed into steam through the filter wall 8, and then discharged through the reaction water outlet N9, and the nuclide is deposited in the salt storage area 10 and discharged through the salt discharge port N12.

[0040] In summary, in view of the low degradation efficiency and large nuclide solidification volume based on the traditional radioactive waste treatment method, the application provides a supercritical water oxidation reactor suitable for radioactive waste treatment, which can realize efficient degradation and nuclide removal of radioactive waste. By combining the radioactive waste treatment technology and the supercritical water oxidation technology, the radioactive waste can be efficiently degraded and the nuclide can be efficiently solidified, thereby realizing inorganic reduction of radioactive waste, which has important application significance for actual radioactive waste treatment.

[0041] The above is only a preferred embodiment of the application and is not intended to limit the application. The application can be variously changed and modified for those skilled in the art. Any modification, equivalent replacement, improvement, etc. within the spirit and principle of the application shall be included in the protection scope of the application.

Claims

1. A supercritical water oxidation reactor suitable for use in the treatment of radioactive waste, characterised in that, It comprises: an end cap part, which comprises an end cap and an annular cover plate, the end cap being connected to the inner ring of the annular cover plate, and the bottom of the annular cover plate being sealingly connected to the flow guide heat insulation cylinder (3); the inner cavity of the end cap is the end cap area (1); the top of the end cap is provided with a high-temperature supercritical water injection port (N1), the sidewall is provided with a primary oxidant inlet (N2) and a primary low-temperature material inlet (N3), and the primary oxidant inlet (N2) is located above the primary low-temperature material inlet (N3); the high-temperature supercritical water injection port (N1), the primary oxidant inlet (N2) and the primary low-temperature material inlet (N3) are in communication with the end cap area (1); a center cylinder, which is provided with a flow guide heat insulation cylinder (3) inside, and the inner cavity of the flow guide heat insulation cylinder (3) is the reaction area (7), which is in communication with the end cap area (1); a cooling wall (11), which is a cylindrical structure with an open top, is sleeved on the bottom of the flow guide heat insulation cylinder (3), and the inner cavity formed by the bottom of the flow guide heat insulation cylinder (3) and the inner side of the cooling wall (11) is the salt storage area (10), which is in communication with the reaction area (7).

2. The supercritical water oxidation reactor suitable for radioactive waste treatment according to claim 1, characterized in that, The side of the annular cover plate is provided with an end cap cooling water inlet (N4) and an end cap cooling water outlet (N7); the end face of the annular cover plate is provided with a secondary low-temperature material inlet (N5) and a secondary oxidant inlet (N6); the secondary low-temperature material inlet (N5) and the secondary oxidant inlet (N6) are in communication with the reaction area (7).

3. The supercritical water oxidation reactor suitable for radioactive waste treatment according to claim 1, characterized by, The reaction area (7) is sequentially provided with a stirrer (2) and a scraper (4) from top to bottom.

4. The supercritical water oxidation reactor suitable for radioactive waste treatment according to claim 1, characterized by, The inner wall of the flow guide heat insulation cylinder (3) is provided with a sacrificial thin lining (9), and a through hole is formed in the cylinder wall of the flow guide heat insulation cylinder (3) and is in communication with the inner side of the cylinder wall of the center cylinder, and a filter wall (8) is arranged in the through hole.

5. The supercritical water oxidation reactor suitable for radioactive waste treatment according to claim 1, 3 or 4, characterized in that, The cylinder wall of the center cylinder is provided with a material preheater (6) and a heat removal heater (5); the material preheater (6) and the heat removal heater (5) are arranged outside the flow guide heat insulation cylinder (3); the side of the center cylinder is provided with a reaction water outlet (N9), which is in communication with the reaction area (7).

6. The supercritical water oxidation reactor suitable for radioactive waste treatment according to claim 1, characterized by, The side of the cooling wall (11) is provided with a cold wall water inlet (N8), a cold wall water outlet (N10), a third oxidant inlet (N11) and a salt discharge port (N12); the third oxidant inlet (N11) and the salt discharge port (N12) are in communication with the salt storage area (10); the third oxidant inlet (N11) is arranged on the sidewall of the cooling wall (11), and the salt discharge port (N12) is arranged on the bottom of the cooling wall (11).

7. The supercritical water oxidation reactor suitable for radioactive waste treatment according to claim 4, characterized by, The filter wall (8) is a filter screen or a sintered metal filter.

8. The supercritical water oxidation reactor suitable for radioactive waste treatment according to claim 1, characterized by, The cylinder wall of the center cylinder is a membrane wall, a coil pipe or a cooling cavity with flow guide function.

9. A supercritical water oxidation process for the treatment of radioactive waste using the reactor according to any one of claims 1 to 8, characterized in that, It comprises the following steps: injecting supercritical water, a primary oxidant and a primary low-temperature material into the end cap area (1), and injecting a secondary oxidant and a secondary low-temperature material into the reaction area (7), so that the primary oxidant, the primary low-temperature material, the secondary oxidant and the secondary low-temperature material are mixed and oxidized in the reaction area (7); After the reaction, the supercritical water is cooled and decompressed into steam through the filter wall (8) and discharged through the reaction water outlet (N9), and the nuclides are deposited in the salt storage area (10) and discharged through the salt discharge port (N12).

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