Incineration-tail gas purification device and method for treating carbon-14-containing radioactive waste

Abstract

The invention relates to an incineration-tail gas purification device and method for treating carbon-14-containing radioactive waste, and belongs to the technical field of radioactive waste treatment. The device comprises an incineration unit, a tail gas purification unit and a gas purification unit; the incineration unit is connected with the feeding assembly through a pipeline, the feeding assembly is used for introducing combustion gas and carbon-14-containing radioactive waste into the incineration unit, and the incineration unit is used for conducting incineration treatment on the carbon-14-containing radioactive waste; the tail gas purification unit comprises a filtering assembly, an acid removal adsorption column and a water removal dryer which are sequentially connected through a pipeline; the gas purification unit comprises a CO2 adsorption / desorption column, a first gas pump, a storage tank and a second gas pump, and the CO2 adsorption / desorption column is used for capturing and releasing radioactive CO2. Efficient solid-to-gas conversion and large-scale volume reduction of carbon-14-containing radioactive waste are achieved, various radioactive elements in tail gas are removed, and high-purity carbon-14-containing CO2 gas is obtained.

Description

Technical Field

[0001] The present invention relates to the technical field of radioactive waste treatment and disposal, and in particular to an incineration-tail gas purification device and method for treating radioactive waste containing carbon-14. Background Art

[0002] Carbon-14 radioactive waste mainly includes radioactive waste graphite generated during the decommissioning of graphite reactors and radioactive waste resin generated during the operation of nuclear power plants.

[0003] Among them, graphite is widely used as a neutron moderator and reflective material in reactors. Under high neutron flux irradiation in the reactor, some non-radioactive nuclides will undergo neutron activation reactions to produce radioactive nuclides, such as 17O (n, α) 14C, 13C (n, γ) 14C and 14N (n, p) 14C to generate 14C (half-life 5730 years). One of the decommissioning routes of the reactor is to restore the site after core dismantling, which meets the long-term safety requirements of relevant regions in my country. However, the radioactive waste graphite discharged from the reactor belongs to medium- and low-level solid waste, which has the characteristics of high activity, high potential and easy ignition, and it is difficult to store temporarily; at the same time, the long half-life of the radioactive nuclides contained makes it unable to meet the requirements of near-surface disposal, and its large amount makes geological disposal also unable to meet the requirements.

[0004] In addition, the main method of purifying C-14 produced during the operation of nuclear power plants is resin adsorption. Therefore, with the continuous development of the nuclear power industry, waste resins containing C-14 have accumulated year by year, forming radioactive waste resins containing carbon-14 similar to radioactive waste graphite, which also face the same problems mentioned above during its treatment and disposal.

[0005] Therefore, the treatment and disposal of carbon-14 radioactive waste has become a global problem. Traditional treatment methods mainly include physical isolation, burial and incineration, but these methods have many problems in practical application, such as large footprint, high environmental risk and low treatment efficiency. Incineration has the advantages of significant volume reduction, good technical feasibility, low treatment cost, and high technical maturity. However, during the incineration process, due to the wide variety of radioactive substances in carbon-14 radioactive waste, the exhaust gas produced by incineration has complex composition and high radioactivity. How to effectively purify the exhaust gas and CO 2 Efficient separation has become a technical bottleneck.

[0006] At present, conventional carbon-14 radioactive waste incineration treatment devices mostly use a multi-tower series adsorption process to filter and adsorb radioactive aerosols, acid gases and water vapor in the tail gas step by step. 2 and O 2 The co-adsorption phenomenon in traditional adsorbents leads to CO 2 The recovery rate is low and it is difficult to convert CO2 The purity is increased to more than 95%. In addition, the traditional adsorption process usually needs to be carried out under low temperature conditions, the equipment is complex, the operation is difficult, and it is not conducive to large-scale industrial application.

[0007] Therefore, it is necessary to develop an efficient tail gas purification device that can be used in large-scale industrial applications. Summary of the invention

[0008] The purpose of the present invention is to provide an incineration-tail gas purification device and method for treating carbon-14 radioactive waste. The device can achieve high-efficiency solid-to-gas conversion of carbon-14 radioactive waste to achieve large-scale volume reduction, and at the same time remove multiple radioactive elements in the waste gas to obtain high-purity carbon-14-containing CO 2 Gas, can be connected to the subsequent chemical exchange method with CO 2 It is of great significance to separate carbon-14 in a certain form and reduce its emission into the environment.

[0009] The purpose of the present invention can be achieved by the following technical solutions: An incineration-tail gas purification device for treating carbon-14 radioactive waste, comprising an incineration unit, a tail gas purification unit and a gas purification unit; The incineration unit is connected to a feed assembly through a pipeline, and the feed assembly is used to pass combustion gas and carbon-14 radioactive waste into the incineration unit, and the incineration unit is used to incinerate the carbon-14 radioactive waste; The tail gas purification unit comprises a filter assembly, an acid removal adsorption column and a water removal dryer which are sequentially connected through pipelines, the filter assembly is connected to the incineration unit through a pipeline, the water removal dryer is connected to the gas purification unit through a pipeline, the filter assembly is used to capture particulate matter, the acid removal adsorption column is used to remove chlorides, and the water removal dryer is used to remove residual water vapor; The gas purification unit includes a CO 2 adsorption / desorption column, a first gas pump, a storage tank and a second gas pump, the CO 2 One end of the adsorption / desorption column is connected to a dehydration dryer through a pipeline. 2 The other end of the adsorption / desorption column is connected to the first gas pump and the second gas pump through pipelines. The first gas pump is far away from the CO 2 One end of the adsorption / desorption column is connected to a storage tank, and the second gas pump is away from the CO 2 One end of the adsorption / desorption column is connected to the feed assembly through a pipeline. 2 Adsorption / desorption columns for capturing and releasing radioactive CO 2 The first gas pump pressurizes the radioactive CO 2 , the tank is used to collect radioactive CO 2The second gas pump circulates the unburned exhaust gas in the incineration unit.

[0010] Furthermore, the feed assembly includes a first feed bin and a second feed bin, the first feed bin is connected to the incineration unit through a pipeline, and the second feed bin is connected to the incineration unit and the second gas pump through a pipeline at the same time, the first feed bin is used to pass carbon-14 radioactive waste into the incineration unit, and the second feed bin is used to pass combustion gas into the incineration unit.

[0011] Furthermore, in the above, an oxygen input pipe is provided at one end of the second feed bin away from the incineration unit.

[0012] Furthermore, the incineration unit includes a tubular furnace, a fluidized bed incinerator and a fixed bed incinerator. The incineration unit is used to incinerate carbon-14 radioactive waste to achieve large-scale volume reduction of carbon-14 radioactive waste, and the generated exhaust gas enters the exhaust gas purification unit through a pipeline.

[0013] Furthermore, the filter assembly includes a first filter and a second filter, one end of the first filter is connected to the incineration unit through a pipeline, the other end of the first filter is connected to the second filter through a pipeline, and the end of the second filter away from the first filter is connected to the acid removal adsorption column through a pipeline; The first filter is used to capture particulate matter, and the second filter is used to capture very fine volatile solid particulate matter.

[0014] Furthermore, in the above, a heat exchange sleeve is provided between the first filter and the second filter, and the heat exchange sleeve is used for cooling the filtered gas.

[0015] As a preferred technical solution, both the first filter and the second filter are metal filters.

[0016] Furthermore, the filler of the acid removal adsorption column includes bicarbonate, carbonate and porous material modified by impregnation with bicarbonate or carbonate solution to improve the removal efficiency.

[0017] Furthermore, the packing of the dehydration dryer can absorb water without reacting with CO. 2 The characteristics of the reaction can be, specifically, the filler of the dehydration dryer is a desiccant such as porous alumina.

[0018] Furthermore, the CO 2 The filler of the adsorption / desorption column is capable of selectively adsorbing CO 2 The adsorption material has the characteristics of adsorption at room temperature and desorption when heated, and can be an organic amine adsorbent or a fluorine-containing ultra-microporous adsorbent, etc., preferably a fluorine-containing ultra-microporous adsorbent.

[0019] Furthermore, the gas purification unit further comprises a three-way valve, the CO 2 The adsorption / desorption column, the first gas pump and the second gas pump are respectively connected to the three-way valve through pipelines.

[0020] In addition, the present invention also provides a method for treating carbon-14-containing radioactive waste, which is carried out using the above-mentioned incineration-tail gas purification device, and the specific steps are as follows: S1. Passing combustion gas and carbon-14 radioactive waste into an incineration unit, closing the first gas pump, opening the second gas pump, and subjecting the carbon-14 radioactive waste to high-temperature combustion treatment through the incineration unit to obtain combustion products; S2, passing the combustion products obtained in step S1 into a filter assembly for filtration to obtain primary purified gas; S3, passing the primary purified gas obtained in step S2 into an acid removal adsorption column and a water removal dryer in sequence to obtain a secondary purified gas; S4, passing the secondary purified gas obtained in step S3 into CO 2 In the adsorption / desorption column, CO 2 Adsorption / desorption column captures CO in secondary purge gas 2 , to obtain captured tail gas; S5, when the CO in the captured tail gas obtained in step S4 is 2 When the concentration is greater than 1 ppm, the captured tail gas is passed into the incineration unit and steps S1 to S4 are repeated; S6, when the CO in the captured tail gas obtained in step S4 2 When the concentration is less than 1ppm, turn off the second gas pump and CO 2 Open the gas inlet valve of the adsorption / desorption column, open the first gas pump and the storage tank, and 2 The adsorption / desorption column is heated, CO 2 The adsorption / desorption column absorbs the gas CO 2 Release into tank.

[0021] Furthermore, in step S1, the combustion gas is selected from air, pure oxygen or a mixture of air and pure oxygen.

[0022] Furthermore, in step S1, the main component of the combustion product is CO 2 , O 2 , CO, 137Cs oxide, 90Sr oxide, 3H 2 O、36Cl 2 , H 36 Cl et al.

[0023] Further, in step S2, the combustion product obtained in step S1 is passed into a first filter, and the first filter captures particulate matter to obtain filtered exhaust gas; The filtered tail gas is passed into the heat exchange sleeve, and the heat exchange sleeve cools the filtered tail gas; The cooled filtered tail gas is then passed into a second filter, which captures the remaining volatile solid particles and a portion of condensed water vapor to obtain primary purified gas.

[0024] The working principle of the present invention is as follows: The present invention designs a small incineration-exhaust gas purification device to achieve high-temperature incineration of waste, purification of radioactive particles and acidic gases in exhaust gas, and finally CO2 removal through fluorine-containing ultra-microporous adsorbent. 2 The tail gas generated during the incineration process passes through a multi-stage purification system to remove particulate matter, acidic gases and moisture, and finally obtains high-purity CO through a room temperature adsorption-heating desorption process. 2 The device not only improves the efficiency of carbon-14 radioactive waste treatment through scientific and reasonable design, but also simplifies CO 2 The purification process reduces secondary pollution to the environment. After being treated by the device and method of the present invention, high-purity CO 2 Used for chemical exchange to achieve carbon isotope 14 enrichment and separation from 12. After treatment, most of the CO 2 Discharge after meeting emission requirements.

[0025] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. The incineration-exhaust gas purification device provided by the present invention can realize the efficient incineration of carbon-14 radioactive waste, realize the efficient solid-to-gas volume reduction of carbon-14 radioactive waste, and at the same time improve the purification and purification of the incineration exhaust gas to obtain high-purity CO 2 Gas, to solve the existing technology of difficult incineration, complex exhaust gas composition and CO 2 To ensure the safety and effectiveness of waste treatment, especially to achieve CO 2 High purity recovery.

[0026] 2. The incineration-exhaust gas purification device provided by the present invention has high incineration efficiency: the tubular furnace design ensures the full combustion of carbon-14 radioactive waste, effectively reduces the generation of incomplete combustion products, and can achieve large-scale volume reduction of carbon-14 radioactive waste.

[0027] 3. The incineration-exhaust gas purification device provided by the present invention removes particulate aerosol, tritium, acidic gas containing 36Cl and water vapor (including 3H 2O), through a multi-stage purification system, it can efficiently remove radioactive particles, acidic gases and moisture in the exhaust gas, and the exhaust gas is thoroughly purified, significantly reducing the risk of environmental pollution.

[0028] 4. The incineration-tail gas purification device provided by the present invention uses a gas purification unit to purify CO 2 Gas is selectively adsorbed / desorbed to obtain high-purity CO 2 Gas, CO 2 The purification effect is excellent; the present invention utilizes the high-efficiency separation characteristics of the fluorine-containing ultra-microporous adsorbent to simplify the CO 2 The purification process can obtain high-purity CO in a single process 2 Gas, CO 2 The recovery rate reaches more than 95%, pure CO 2 The chemical exchange method can be used to separate carbon isotopes carbon-14 and carbon-12. After treatment, most of the CO 2 The discharge can meet the discharge requirements.

[0029] 5. Reliable experimental verification: Through thermal verification of a small laboratory test bench, the effectiveness and reliability of the incineration-exhaust gas purification device provided by the present invention in treating carbon-14 radioactive waste have been proved, providing solid technical support for subsequent industrial applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The accompanying drawings are part of the present invention and are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention, but do not constitute an improper limitation of the present invention. Obviously, the accompanying drawings described below are only some embodiments. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without creative work.

[0031] In the attached picture: Figure 1 It is a schematic diagram of the structure of the incineration-tail gas purification device in the present invention; Figure 2 A flow chart of a method for treating radioactive waste containing carbon-14 in the present invention; Figure 3 This is a schematic table of product gas detection results of Example 2, Example 3 and Comparative Example 1 in the present invention.

[0032] Description of the accompanying figures: 1. first feed bin, 2. oxygen input pipe, 3. second feed bin, 4. incineration unit, 5. combustion products, 6. first filter, 7. particulate matter, 8. filtered tail gas, 9. heat exchange sleeve, 10. cooling water, 11. second filter, 12. acid removal adsorption column, 13. primary purified gas, 14. dehydration dryer, 15. secondary purified gas, 16. CO2 Adsorption / desorption column, 17, capture tail gas, 18, adsorption gas CO 2 , 19. three-way valve, 21. first gas pump, 22. storage tank, 24. second gas pump. DETAILED DESCRIPTION

[0033] The present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0034] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0035] In the description of the present invention, it should be noted that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first" and "second" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance.

[0036] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0037] The experimental methods in the following examples are conventional methods unless otherwise specified.

[0038] Unless otherwise specified, the materials and reagents used in the following examples can be obtained from commercial sources.

[0039] In conjunction with the accompanying drawings, some embodiments of the present invention are described in detail below. In the absence of conflict, the following embodiments and features in the embodiments may be combined with each other.

[0040] Example 1 See also Figure 1This embodiment provides an incineration-tail gas purification device for treating carbon-14 radioactive waste, wherein the carbon-14 radioactive waste includes but is not limited to radioactive graphite waste, and the tail gas purification device includes an incineration unit 4, a tail gas purification unit and a gas purification unit. The incineration unit 4 is connected to a feed assembly through a pipeline, and the feed assembly is used to pass combustion gas and radioactive graphite waste into the incineration unit 4, and the incineration unit 4 is used to incinerate the radioactive graphite waste; The tail gas purification unit comprises a filter assembly, an acid removal adsorption column 12 and a water removal dryer 14 which are sequentially connected through pipelines, wherein the filter assembly is connected to the incineration unit 4 through a pipeline, and the water removal dryer 14 is connected to the gas purification unit through a pipeline, wherein the filter assembly is used to capture particulate matter, the acid removal adsorption column 12 is used to remove chlorides, and the water removal dryer 14 is used to remove residual water vapor; The gas purification unit includes a CO 2 The adsorption / desorption column 16, the first gas pump 21, the storage tank 22 and the second gas pump 24, the CO 2 One end of the adsorption / desorption column 16 is connected to the dehydration dryer 14 through a pipeline. 2 The other end of the adsorption / desorption column 16 is connected to a first gas pump 21 and a second gas pump 24 through pipelines. The first gas pump 21 is far away from the CO 2 One end of the adsorption / desorption column 16 is connected to the storage tank 22, and the second gas pump 24 is away from the CO 2 One end of the adsorption / desorption column 16 is connected to the feed assembly through a pipeline. 2 Adsorption / desorption column 16 is used to capture and release radioactive CO 2 The first gas pump 21 pressurizes the radioactive CO 2 The storage tank 22 is used to collect radioactive CO 2 The second gas pump 24 circulates the unburned exhaust gas in the incineration unit 4.

[0041] In this embodiment, the feeding assembly includes a first feeding bin 1 and a second feeding bin 3. The first feeding bin 1 is connected to the incineration unit 4 through a pipeline, and the second feeding bin 3 is connected to the incineration unit 4 and the second gas pump 24 through a pipeline at the same time. The first feeding bin 1 is used to pass radioactive graphite waste into the incineration unit 4, and the second feeding bin 3 is used to pass combustion gas into the incineration unit 4.

[0042] In this embodiment, an oxygen input pipe 2 is provided at one end of the second feed bin 3 away from the incineration unit 4 .

[0043] In this embodiment, the incineration unit 4 includes a tubular furnace, a fluidized bed incinerator and a fixed bed incinerator. The incineration unit 4 is used to incinerate radioactive graphite waste to achieve large-scale volume reduction of waste graphite, and the generated exhaust gas enters the exhaust gas purification unit through a pipeline.

[0044] In this embodiment, the filter assembly includes a first filter 6 and a second filter 11, one end of the first filter 6 is connected to the incineration unit 4 through a pipeline, the other end of the first filter 6 is connected to the second filter 11 through a pipeline, and the end of the second filter 11 away from the first filter 6 is connected to the acid removal adsorption column 12 through a pipeline; The first filter 6 is used to capture particulate matter, and the second filter 11 is used to capture extremely fine volatile solid particulate matter.

[0045] In this embodiment, a heat exchange sleeve 9 is provided between the first filter 6 and the second filter 11, and the heat exchange sleeve 9 is used to cool the filtered gas.

[0046] In this embodiment, the first filter 6 and the second filter 11 are both metal filters.

[0047] In this embodiment, the filler of the acid removal adsorption column 12 includes bicarbonate, carbonate and porous material modified by impregnation with bicarbonate or carbonate solution to improve the removal efficiency.

[0048] In this embodiment, the packing of the dehydration dryer 14 is sufficient to absorb water without reacting with CO. 2 The characteristics of the reaction can be, specifically, the filler of the dehydration dryer 14 is a desiccant such as porous alumina.

[0049] In this embodiment, the CO 2 The filler of the adsorption / desorption column 16 is capable of selectively adsorbing CO 2 The adsorption material has the characteristics of adsorption at room temperature and desorption when heated, and can be an organic amine adsorbent or a fluorine-containing ultra-microporous adsorbent, etc., preferably a fluorine-containing ultra-microporous adsorbent.

[0050] In this embodiment, the gas purification unit further includes a three-way valve 19. 2 The adsorption / desorption column 16, the first gas pump 21 and the second gas pump 24 are respectively connected to the three-way valve 19 through pipelines.

[0051] Example 2 This embodiment provides a method for treating carbon-14 radioactive waste, which is carried out using the incineration-tail gas purification device described in Example 1. In this embodiment, the carbon-14 radioactive waste is taken as radioactive graphite, and the specific steps are as follows: S1, take the specific activity as 100 g of radioactive graphite particles were placed in a tube furnace, the first gas pump 21 outside the storage tank 22 was turned off, the second gas pump 24 was turned on, 0.2 L / min of pure oxygen was used as the carrier gas and protective atmosphere, and the temperature of the tube furnace was raised to 850 ° C for combustion. The combustion products included O 2 , CO 2 , CO, chlorides, water vapor and volatile solid substances are sent to the first filter 6 through the gas path at the tail end of the tubular furnace, and the volatile solids are initially intercepted to obtain filtered tail gas 8.

[0052] S2. The filtered tail gas 8 is passed into the heat exchange sleeve 9. The heat exchange sleeve 9 cools the filtered tail gas 8 to 80° C. and sends it to the second filter 11. At this time, the second filter 11 will intercept the residual volatile solids and a part of the condensed water vapor in the gas to obtain the primary purified gas 13.

[0053] S3, the primary purified gas 13 is respectively passed through the acid removal adsorption column 12 filled with potassium carbonate and the water removal dryer 14 filled with macroporous alumina particles at a rate of 0.2 L / min under the action of the second gas pump 24 to obtain a gas containing only carrier gas O 2 , incompletely burned CO and CO 2 The secondary purified gas 15.

[0054] S4, the secondary purified gas 15 is pumped through a 25°C CO 2 Adsorption / desorption column 16, CO 2 The adsorption / desorption column 16 captures CO in the secondary purified gas 15 2 , after CO 2 The secondary purified gas 15 captured by the adsorption / desorption column 16 only has CO and O 2 , that is, capturing tail gas 17; S5, when the CO in the captured tail gas 17 obtained in step S4 is 2 When the concentration is greater than 1 ppm, the gas is returned to the tube furnace through the second gas pump 24 to continue burning, and steps S1 to S4 are repeated; S6, when the CO in the captured tail gas 17 obtained in step S4 is 2 When the concentration is less than 1 ppm, close the inlet valve of the oxygen inlet pipe 2, the second gas pump 24 and the CO 2 The air inlet valve of the adsorption / desorption column 16 is opened, and the air inlet valves of the first gas pump 21 and the storage tank 22 are opened to start the CO 2 The heating procedure of the adsorption / desorption column 16 is 2 The adsorbent particles in the adsorption / desorption column 16 are heated to 80°C, and the CO 2 The adsorption / desorption column 16 absorbs the gas CO 218 is released into the storage tank 22, and the product gas CO is collected in the storage tank 22 2 .

[0055] The final product gas detection results are as attached. Figure 3 As shown, radioactive CO 2 The purity reaches 98% and the total activity is about The specific activity under standard conditions is about 535 Bq / L, indicating that the radioactive C-14 in the waste graphite has been fully converted into high-purity C-14-containing CO 2 gas.

[0056] Example 3 This embodiment provides a method for treating carbon-14 radioactive waste, which is carried out using the incineration-tail gas purification device described in Example 1. In this embodiment, the carbon-14 radioactive waste is also taken as radioactive graphite as an example, and the specific steps are as follows: S1, take the specific activity as 100 g of radioactive graphite particles were placed in a tube furnace, the first gas pump 21 outside the storage tank 22 was turned off, the second gas pump 24 was turned on, 0.3 L / min of 50% oxygen and 50% nitrogen were used as carrier gas and protective atmosphere, the tube furnace was heated to 850 ° C for combustion, and the combustion products included O 2 、N 2 , CO 2 , CO, chlorides, water vapor and volatile solid substances are sent to the first filter 6 through the gas path at the tail end of the tubular furnace, and the volatile solids are initially intercepted to obtain filtered tail gas 8.

[0057] S2. The filtered tail gas 8 is passed into the heat exchange sleeve 9. The heat exchange sleeve 9 cools the filtered tail gas 8 to 80° C. and sends it to the second filter 11. At this time, the second filter 11 will intercept the residual volatile solids and a part of the condensed water vapor in the gas to obtain the primary purified gas 13.

[0058] S3, the primary purified gas 13 is respectively passed through the acid removal adsorption column 12 filled with potassium carbonate and the water removal dryer 14 filled with macroporous alumina particles at a rate of 0.3 L / min under the action of the second gas pump 24 to obtain a gas containing only carrier gas N 2 +O 2 , incompletely burned CO and CO 2 The secondary purified gas 15.

[0059] S4, the secondary purified gas 15 is passed through a 25°C CO 2 Adsorption / desorption column 16, CO 2 The adsorption / desorption column 16 captures CO in the secondary purified gas 15 2 , after CO2 The secondary purified gas 15 captured by the adsorption / desorption column 16 only has N 2 , CO and CO 2 , that is, capturing tail gas 17; S5, when the CO in the captured tail gas 17 obtained in step S4 is 2 When the concentration is greater than 1 ppm, the gas is returned to the tube furnace through the second gas pump 24 to continue burning, and steps S1 to S4 are repeated; S6, when the CO in the captured tail gas 17 obtained in step S4 is 2 When the concentration is less than 1 ppm, close the inlet valve of the oxygen inlet pipe 2, the second gas pump 24 and the CO 2 The air inlet valve of the adsorption / desorption column 16 is opened, and the air inlet valves of the first gas pump 21 and the storage tank 22 are opened to start the CO 2 The heating procedure of the adsorption / desorption column 16 is 2 The adsorbent particles in the adsorption / desorption column 16 are heated to 80°C, and the CO 2 The adsorption / desorption column 16 absorbs the gas CO 2 18 is released into the storage tank 22, and the product gas CO is collected in the storage tank 22 2 .

[0060] The final product gas detection results are as attached. Figure 3 As shown, radioactive CO 2 The purity reaches 98% and the total activity is about , the specific activity under standard conditions is about 487Bq / L. This indicates that the radioactive C-14 in the waste graphite has been basically converted into high-purity C-14-containing CO 2 gas.

[0061] Comparative Example 1 This comparative example provides a method for treating carbon-14 radioactive waste. In this example, radioactive graphite is used as an example of carbon-14 radioactive waste. The specific steps are as follows: S1, take the specific activity as 100 g of radioactive graphite particles were placed in a tube furnace, the first gas pump 21 outside the storage tank 22 was turned off, the second gas pump 24 was turned on, 0.2 L / min of pure oxygen was used as the carrier gas and protective atmosphere, and the temperature of the tube furnace was raised to 850 ° C for combustion. The combustion products included O 2 , CO 2 , CO, chlorides, water vapor and volatile solid substances are sent to the first filter 6 through the gas path at the tail end of the tubular furnace, and the volatile solids are initially intercepted to obtain filtered tail gas 8.

[0062] S2. The filtered tail gas 8 is passed into the heat exchange sleeve 9. The heat exchange sleeve 9 cools the filtered tail gas 8 to 80° C. and sends it to the second filter 11. At this time, the second filter 11 will intercept the residual volatile solids and a part of the condensed water vapor in the gas to obtain the primary purified gas 13.

[0063] S3, the primary purified gas 13 is passed through a 25°C CO at a rate of 0.2 L / min under the action of the second gas pump 24. 2 Adsorption / desorption column 16, CO 2 The adsorption / desorption column 16 captures CO in the primary purified gas 13 2 , after CO 2 The components of the captured tail gas 17 after being captured by the adsorption / desorption column 16 are CO, O 2 and small amounts of water vapor and chlorides; S4, when the CO in the captured tail gas 17 obtained in step S3 2 When the concentration is greater than 1 ppm, the gas is returned to the tube furnace through the second gas pump 24 to continue burning, and steps S1 to S3 are repeated; S5, when the CO in the captured tail gas 17 obtained in step S3 is 2 When the concentration is less than 1 ppm, close the inlet valve of the oxygen inlet pipe 2, the second gas pump 24 and the CO 2 The air inlet valve of the adsorption / desorption column 16 is opened, and the air inlet valves of the first gas pump 21 and the storage tank 22 are opened to start the CO 2 The heating procedure of the adsorption / desorption column 16 is 2 The adsorbent particles in the adsorption / desorption column 16 are heated to 80°C, and the CO 2 The adsorption / desorption column 16 absorbs the gas CO 2 18 is released into the storage tank 22, and the product gas CO is collected in the storage tank 22 2 .

[0064] The final product gas detection results are as attached. Figure 3 As shown in the table, radioactive CO 2 The purity reaches 87% and the total activity is about , the specific activity under standard conditions is about 437Bq / L. This shows that if the tail gas after burning in the waste graphite is not purified by secondary purification, it is difficult to be fully converted into high-purity CO containing C-14. 2 gas.

[0065] In a feasible embodiment, the carbon-14 radioactive waste described in the present invention includes but is not limited to radioactive waste graphite and radioactive waste resin; the present application describes the radioactive waste graphite, and the treatment method of the radioactive waste resin is the same as the treatment method of the radioactive waste graphite in the above-mentioned embodiments 1-3 and comparative example 1, which will not be repeated here. The above description of the embodiments is to facilitate ordinary technicians in this technical field to understand and use the invention. It is obvious that those familiar with the technology in this field can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative labor. Therefore, the present invention is not limited to the above-mentioned embodiments, and improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the present invention should be within the scope of protection of the present invention.

Claims

1. An incineration-exhaust gas purification device for treating carbon-14 radioactive waste, characterized in that: It includes an incineration unit (4), an exhaust gas purification unit and a gas purification unit; The incineration unit (4) is connected to a feed assembly via a pipeline, the feed assembly is used to pass combustion gas and carbon-14 radioactive waste into the incineration unit (4), and the incineration unit (4) is used to incinerate the carbon-14 radioactive waste; The tail gas purification unit comprises a filter assembly, an acid removal adsorption column (12) and a water removal dryer (14) which are sequentially connected via a pipeline, the filter assembly is connected to the incineration unit (4) via a pipeline, the water removal dryer (14) is connected to the gas purification unit via a pipeline, the filter assembly is used to capture particulate matter, the acid removal adsorption column (12) is used to remove chlorides, and the water removal dryer (14) is used to remove residual water vapor; The gas purification unit comprises a CO2 adsorption / desorption column (16), a first gas pump (21), a storage tank (22) and a second gas pump (24); one end of the CO2 adsorption / desorption column (16) is connected to the dehydration dryer (14) via a pipeline; the other end of the CO2 adsorption / desorption column (16) is connected to the first gas pump (21) and the second gas pump (24) via pipelines, respectively; one end of the first gas pump (21) away from the CO2 adsorption / desorption column (16) is connected to the storage tank (22); one end of the second gas pump (24) away from the CO2 adsorption / desorption column (16) is connected to a feed assembly via a pipeline; the CO2 adsorption / desorption column (16) is used to capture and release radioactive CO2; the first gas pump (21) pressurizes the radioactive CO2; the storage tank (22) is used to collect the radioactive CO2; and the second gas pump (24) circulates unburned tail gas in the incineration unit (4).

2. The incineration-exhaust gas purification device for treating carbon-14 radioactive waste according to claim 1, characterized in that: The feed assembly comprises a first feed bin (1) and a second feed bin (3); the first feed bin (1) is connected to an incineration unit (4) via a pipeline; the second feed bin (3) is connected to both the incineration unit (4) and a second gas pump (24) via a pipeline; the first feed bin (1) is used to pass the carbon-14 radioactive waste into the incineration unit (4); and the second feed bin (3) is used to pass the combustion gas into the incineration unit (4).

3. The incineration-exhaust gas purification device for treating carbon-14 radioactive waste according to claim 2, characterized in that: An oxygen input pipe (2) is provided at one end of the second feed bin (3) away from the incineration unit (4).

4. The incineration-exhaust gas purification device for treating carbon-14 radioactive waste according to claim 1, characterized in that: The filter assembly comprises a first filter (6) and a second filter (11); one end of the first filter (6) is connected to the incineration unit (4) via a pipeline; the other end of the first filter (6) is connected to the second filter (11) via a pipeline; and the end of the second filter (11) away from the first filter (6) is connected to the acid removal adsorption column (12) via a pipeline; The first filter (6) is used to capture particulate matter, and the second filter (11) is used to capture extremely fine volatile solid particulate matter.

5. The incineration-exhaust gas purification device for treating carbon-14 radioactive waste according to claim 4, characterized in that: A heat exchange sleeve (9) is provided between the first filter (6) and the second filter (11), and the heat exchange sleeve (9) is used to cool the filtered gas.

6. The incineration-exhaust gas purification device for treating carbon-14 radioactive waste according to claim 1, characterized in that: The filler of the acid removal adsorption column (12) includes bicarbonate, carbonate and a porous material modified by impregnation with a bicarbonate or carbonate solution; The filler of the dehydration dryer (14) is porous alumina; The filler of the CO2 adsorption / desorption column (16) is a fluorine-containing ultra-microporous CO2 adsorbent.

7. The incineration-exhaust gas purification device for treating carbon-14 radioactive waste according to claim 1, characterized in that: The gas purification unit further comprises a three-way valve (19), and the CO2 adsorption / desorption column (16), the first gas pump (21) and the second gas pump (24) are respectively connected to the three-way valve (19) via pipelines.

8. A method for treating carbon-14 radioactive waste, characterized in that: The incineration-tail gas purification device as described in any one of claims 1 to 7 is used, and the specific steps are as follows: S1, passing combustion gas and carbon-14-containing radioactive waste into an incineration unit (4), closing the first gas pump (21), opening the second gas pump (24), and subjecting the carbon-14-containing radioactive waste to high-temperature combustion treatment through the incineration unit (4) to obtain a combustion product (5); S2, passing the combustion product (5) obtained in step S1 into a filter assembly for filtration to obtain primary purified gas (13); S3, passing the primary purified gas (13) obtained in step S2 into the acid removal adsorption column (12) and the water removal dryer (14) in sequence to obtain secondary purified gas (15); S4, passing the secondary purified gas (15) obtained in step S3 into a CO2 adsorption / desorption column (16), wherein the CO2 adsorption / desorption column (16) captures CO2 in the secondary purified gas (15) to obtain captured tail gas (17); S5. When the CO2 concentration in the captured tail gas (17) obtained in step S4 is greater than 1 ppm, the captured tail gas (17) is introduced into the incineration unit (4), and steps S1 to S4 are repeated; S6. When the CO2 concentration in the captured tail gas (17) obtained in step S4 is less than 1 ppm, the second gas pump (24) and the gas inlet valve of the CO2 adsorption / desorption column (16) are closed, and the first gas pump (21) and the storage tank (22) are opened to heat the CO2 adsorption / desorption column (16), so that the CO2 adsorption / desorption column (16) releases the adsorbed gas CO2 (18) into the storage tank (22).

9. A method for treating carbon-14 radioactive waste according to claim 8, characterized in that: In step S1, the combustion gas is selected from air, pure oxygen or a mixture of air and pure oxygen.

10. A method for treating carbon-14 radioactive waste according to claim 8, characterized in that: In step S2, the combustion product (5) obtained in step S1 is passed into a first filter (6), and the first filter (6) captures particulate matter to obtain filtered exhaust gas (8); Passing the filtered tail gas (8) into the heat exchange sleeve (9), the heat exchange sleeve (9) cooling the filtered tail gas (8); The cooled filtered tail gas (8) is then passed into a second filter (11), and the second filter (11) captures the remaining volatile solid particles and a portion of condensed water vapor to obtain primary purified gas (13).

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