A system for separating nuclides and acids from highly acidic radioactive waste liquid

Abstract

The present invention provides a system for separating nuclides and acids in high-acid radioactive waste liquid, including a plurality of diffusion dialysis membrane stacks, wherein the diffusion dialysis membrane stack is provided with two groups of partitions, an ion exchange membrane is provided in the middle of the partition, the ion exchange membrane adopts an anion exchange membrane or a cation exchange membrane, and the diffusion dialysis membrane stack is provided with an acid inlet, a raw water inlet, a residual acid outlet and an acid production outlet. According to the different anion and cation compositions of nuclides at different acidities, different ion exchange membranes are selected to effectively play the advantages of anion diffusion dialysis and cation diffusion dialysis, and have high acid separation efficiency and nuclide separation efficiency. Partitions are provided on both sides of the ion exchange membrane to form an intermediate buffer zone as a separation between high-concentration nuclides and low-radiation acid production after acid separation, thereby reducing the radiation of nuclides to the external environment, especially the risk of membrane rupture will not have a significant impact on the output acid, and also increase the safety of process operation and maintenance.

Description

Technical Field

[0001] The invention relates to the technical field of radioactive wastewater treatment, in particular to a system for separating nuclides and acids in highly acidic radioactive waste liquid. Background Art

[0002] High-acid radioactive waste liquid refers to an acid solution containing radionuclides, usually nitric acid or hydrochloric acid, with an acid content of 1 to 7 mg / L. It contains a large number of radionuclides of various types and has strong radioactivity. In order to meet the needs of production separation and subsequent environmental protection, it is necessary to separate the radionuclides and heavy metals from the acid. Most traditional separation methods adopt neutralization precipitation, distillation, ion exchange resin method, etc., but because of the high acidity, the neutralization method will consume a lot of alkali and produce a large number of secondary pollutants; in the distillation method, due to the high acidity, the distillation consumes a lot of energy and the equipment requirements are extremely high, and because of the large number of radionuclides and heavy metals, scaling occurs, affecting heat transfer and the risk of explosion at the limit concentration, and secondary pollutants will also be generated due to cleaning equipment; the ion exchange resin method currently has no industrial special resin that can extract heavy metals from high-concentration acids. Among them, the extraction resin is only used for analysis, the price is extremely expensive, and it cannot be regenerated, and a large number of secondary pollutants are generated.

[0003] Membrane treatment, especially diffusion dialysis technology, has become a relatively convenient and easy technology. Diffusion dialysis technology refers to a dialysis separation technology that uses different concentrations of ions on both sides of the ion exchange membrane, using concentration effects and the Donnan effect to achieve molecular diffusion. According to the different membranes used, it can be divided into cation exchange membrane diffusion dialysis, which is mainly used for alkali recovery containing organic acid radicals; anion exchange membrane diffusion dialysis, which is mainly used for acid recovery containing heavy metal ions. The specific principle is as follows Figure 1 , Figure 2 .

[0004] The traditional diffusion dialysis technology is used to separate nuclides and acids in highly acidic radioactive waste liquid, and it mainly faces the following difficulties:

[0005] (1) The coexistence of cations and anions of nuclides makes the retention rate of nuclides in traditional diffusion dialysis low. Nuclides exist in different valence states, and in different acid concentrations, the complex ions formed with acids show different content compositions and valence states. Because in diffusion dialysis, anion exchange membranes can only retain cationic heavy metals and pass anionic heavy metals; similarly, cation exchange membranes can only retain anionic heavy metals and pass cationic heavy metals.

[0006] (2) There is a risk of leakage in the treatment of high-acid radionuclides in traditional diffusion dialysis. Traditional diffusion dialysis uses a membrane for acid exchange on both sides, with one side being the original acid chamber with a higher level of radionuclides and the other side being the original water chamber with a small amount of radionuclides. There is only one membrane as a partition. If there is leakage on one side during the treatment process, it will directly cause the entire process to fail, especially affecting the output acid. It is particularly unsuitable for high-acid radioactive liquids.

[0007] The present invention is proposed in view of the above problems. Summary of the invention

[0008] The purpose of the present invention is to provide a system for separating nuclides and acids in high-acid radioactive waste liquid. The system has high acid separation efficiency and nuclide separation efficiency, can separate high-concentration nuclides from low-radiation acid production after acid separation, reduce the radiation of nuclides to the external environment, and especially the risk of membrane rupture will not have a significant impact on the output acid, thereby increasing the safety of process operations.

[0009] The present invention provides a system for separating nuclides and acids in high-acid radioactive waste liquid, comprising a plurality of diffusion dialysis membrane stacks, wherein the diffusion dialysis membrane stacks are provided with two groups of partitions, an ion exchange membrane is provided in the middle of the partitions, and the ion exchange membrane is an anion exchange membrane or a cation exchange membrane, and the diffusion dialysis membrane stacks are provided with an acid inlet, a raw water inlet, a residual acid outlet and an acid production outlet.

[0010] Furthermore, the partition is provided with an upper flow port and a lower flow port. According to the processing capacity and processing efficiency of the process, a plurality of the above-mentioned diffusion dialysis membrane stacks can be connected in parallel to increase the separation exchange area. Each diffusion dialysis membrane stack can adjust the flow of inlet and outlet water according to the different compositions of cation and cation complex ions of different radionuclides under different acid concentration conditions to adjust the acidity value, thereby improving the interception rate of heavy metals.

[0011] Furthermore, it includes a plurality of diffusion dialysis units, each of which includes two connected diffusion dialysis membrane stacks, wherein the ion exchange membranes of the two diffusion dialysis membrane stacks are cation exchange membranes and anion exchange membranes, respectively, and the residual acid outlet of the cation exchange membrane diffusion dialysis membrane stack is connected to the acid inlet of the anion exchange membrane diffusion dialysis membrane stack through a pipeline, and the raw water inlet of the cation exchange membrane diffusion dialysis membrane stack is connected to the acid production outlet of the anion exchange membrane diffusion dialysis membrane stack through a pipeline.

[0012] Furthermore, an acidity meter is provided on the pipeline connecting the cation exchange membrane diffusion dialysis membrane stack and the anion exchange membrane diffusion dialysis membrane stack.

[0013] Furthermore, it comprises at least two connected diffusion dialysis units, the acid production outlet of the cation exchange membrane diffusion dialysis membrane stack of the first diffusion dialysis unit is connected to the acid inlet of the cation exchange membrane diffusion dialysis membrane stack of the second diffusion dialysis unit through a pipeline, and the residual acid outlet of the anion exchange membrane diffusion dialysis membrane stack of the second diffusion dialysis unit is connected to the raw water inlet of the anion exchange membrane diffusion dialysis membrane stack of the first diffusion dialysis unit through a pipeline.

[0014] Furthermore, a circulation pump is provided on the pipeline connecting the anion exchange membrane diffusion dialysis membrane stack of the first diffusion dialysis unit and the anion exchange membrane diffusion dialysis membrane stack of the second diffusion dialysis unit.

[0015] The above-mentioned diffusion dialysis unit combination can take into account the different anion and cation compositions of nuclides at different acidities, effectively exert the overall advantages of anion diffusion dialysis and cation diffusion dialysis, and has high acid separation efficiency and nuclide separation efficiency.

[0016] Furthermore, the diffusion dialysis membrane stack is prepared by screw extrusion or extruder extrusion.

[0017] Furthermore, the dimensions of the ion exchange membrane are: 500 mm in width and 200 mm in length.

[0018] Furthermore, each group of the separators is composed of 40 membrane separators, and each membrane separator has a length of 200 mm, a width of 400 mm, and a thickness of 6 mm.

[0019] Furthermore, the inner grid thickness of the membrane separator is 5 mm.

[0020] In summary, the present invention has the following advantages compared with the prior art:

[0021] (1) The system for separating nuclides and acids in highly acidic radioactive waste liquid provided by the present invention adopts a diffusion dialysis membrane stacking system with different interception performances of ions for effective separation. Different ion exchange membranes are selected according to the different anion and cation compositions of nuclides at different acidities, effectively giving play to the advantages of anion diffusion dialysis and cation diffusion dialysis, and having high acid separation efficiency and nuclide separation efficiency.

[0022] (2) The system for separating nuclides and acids in high-acid radioactive waste liquid provided by the present invention has partitions on both sides of the ion exchange membrane to form an intermediate buffer zone as a separation between high-concentration nuclides and low-radiation acid produced after acid separation. This can reduce the radiation of nuclides to the external environment, especially the risk of membrane rupture will not have a significant impact on the produced acid, and also increases the safety of process operation and maintenance. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0024] Figure 1 It is a schematic diagram of anion diffusion dialysis in the prior art;

[0025] Figure 2 It is a schematic diagram of the cation diffusion dialysis principle in the prior art;

[0026] Figure 3 This is a schematic structural diagram of the first cation exchange membrane diffusion dialysis membrane stack in Example 1 of the present invention;

[0027] Figure 4 This is a schematic diagram of the separation principle of the waste liquid treatment process of the first cation exchange membrane diffusion dialysis membrane stack in Example 1 of the present invention;

[0028] Figure 5 This is a schematic diagram of the connection of the first diffusion dialysis unit in Example 3 of the present invention;

[0029] Figure 6 This is the wastewater treatment process balance diagram of the first diffusion dialysis unit in Example 3 of the present invention;

[0030] Figure 7 Schematic diagram of the connection of the nuclide and acid separation system in Example 4 of the present invention.

[0031] Explanation of the figure marks: 1-first diffusion dialysis unit, 101-first cation exchange membrane diffusion dialysis membrane stack, 1011-partition, 1012-ion exchange membrane, 102-first anion exchange membrane diffusion dialysis membrane stack, 2-second diffusion dialysis unit, 201-second cation exchange membrane diffusion dialysis membrane stack, 202-second anion exchange membrane diffusion dialysis membrane stack, 3-acidity meter, 4-circulation pump. DETAILED DESCRIPTION

[0032] It should be noted that the following detailed descriptions are illustrative and are intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present application belongs.

[0033] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form also includes the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this description, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0034] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0035] Example 1

[0036] A system for separating nuclides and acids in highly acidic radioactive waste liquid, comprising a diffusion dialysis membrane stack, such as Figure 3 As shown. The ion exchange membrane 1012 is a cation exchange membrane, and a partition 1011 is provided on both sides of the cation exchange membrane. Two liquid media flow on both sides of the ion exchange membrane 1012, and the ion exchange membrane 1012 plays a role of separation. The diffusion dialysis membrane stack is provided with an acid inlet and an acid production outlet at one end, and a residual acid outlet and a raw water inlet ( Figure 1 In the figure, Ca0 indicates the acid inlet, Cw0 indicates the raw water inlet, Ca1 indicates the residual acid outlet, and Cw1 indicates the acid production outlet). The partitions 1011 are all provided with an upper flow port and a lower flow port. The upper flow port of one group of partitions is connected to the acid inlet, and the lower flow port is connected to the residual acid outlet; the upper flow port of another group of partitions is connected to the acid production outlet, and the lower flow port is connected to the raw water inlet.

[0037] In order to better distinguish it from the diffusion dialysis membrane stacks in other embodiments, the diffusion dialysis membrane stack here is named as the first cation diffusion dialysis membrane stack 101 .

[0038] The membrane module is automatically loaded and unloaded, and a continuous flat plate diffusion dialysis cation exchange membrane is used. The width of the cation exchange membrane is 500mm, and the total membrane length is 200m. The partition is composed of 40 membrane partitions. The membrane partition is GN-WNC, and the size of the membrane partition is 400mm wide, 200mm long, 6mm thick, and the inner grid thickness is 5mm.

[0039] The diffusion dialysis membrane stack can be made by screw extrusion or by extrusion by an extruder. In view of the radiation environment, the present invention recommends the use of an extruder.

[0040] The first cation exchange membrane diffusion dialysis membrane stack 101 is used to separate nuclides and acids: the water source to be treated is a high-acid high-level waste liquid produced by spent fuel reprocessing, wherein the composition is: 7 mol / L nitric acid, 1 g / L U (uranium) content, activity: >109 Bq / L, as shown in Table 1. The diaphragm metering pump is used for feeding, wherein the flow rate of the raw acid pump is 500 mL / min, and the flow rate of the raw water pump is 600 mL / min; after 2 hours of operation, the acid production and residual acid effluent meet the index requirements, as shown in Table 1, and the principle is as follows Figure 4 As shown (in the figure, membrane C represents a cation exchange membrane).

[0041] Table 1 CDD inlet and outlet water quality and acid salt recovery rate

[0042]

[0043] It can be seen from Table 1 that the UO2(NO3)4 in the original acid and residual acid -2 The complex anion is relatively high, which is consistent with the literature that the complex anion is the main component under acidic conditions above 4N; while UO2(NO3)4 -2 Only 0.04mol / L, which means that the above diffusion dialysis membrane stack has a high retention rate for anions when using cation exchange membrane, and the recovery rate is as high as 96%. Similarly, UO2 +2 The retention rate of the membrane is very low and the recovery rate is only 80%.

[0044] Example 2

[0045] A system for separating nuclides and acids in high-acid radioactive waste liquid is basically the same as the technical solution of Example 1, except that: the ion exchange membrane adopts a continuous flat plate diffusion dialysis anion exchange membrane ADP120. The diffusion dialysis membrane stack is named the first anion exchange membrane diffusion dialysis membrane stack 102. The first anion diffusion dialysis membrane stack 102 is used to separate nuclides and acids in high-acid radioactive waste liquid. The treated waste liquid and process are the same as those in Example 1. The obtained inlet and outlet water quality, water volume and recovery rate are shown in Table 2.

[0046] Table 2 ADD inlet and outlet water quality and acid salt recovery rate

[0047]

[0048] It can be seen from Table 2 that the UO2(NO3)4 in the original acid and residual acid -2 The complex anion is relatively high, which is consistent with the literature that under acidic conditions above 4N, the complex anion is the main component. -2The anion exchange membrane in the diffusion dialysis membrane stack has a very low retention rate for anions, and its recovery rate is as low as 70%. +2 The interception rate is very high, and the recovery rate is 90%.

[0049] Example 3

[0050] A system for separating nuclides and acids in highly acidic radioactive waste liquid, such as Figure 5 As shown, it is composed of a diffusion dialysis unit, named as the first diffusion dialysis unit 1. The diffusion dialysis unit is composed of the first cation exchange membrane diffusion dialysis membrane stack 101 in Example 1 and the first anion exchange membrane diffusion dialysis membrane stack 102 in Example 2.

[0051] The residual acid outlet of the first cation exchange membrane diffusion dialysis membrane stack 101 is connected to the acid inlet of the first anion exchange membrane diffusion dialysis membrane stack 102 through a pipeline, and the raw water inlet of the first cation exchange membrane diffusion dialysis membrane stack 101 is connected to the acid production outlet of the first anion exchange membrane diffusion dialysis membrane stack 102 through a pipeline. The pipelines connecting the first cation exchange membrane diffusion dialysis membrane stack 101 and the first anion exchange membrane diffusion dialysis membrane stack 102 are both installed with an acidity meter 3.

[0052] The first diffusion dialysis unit 1 is used to separate the nuclides and acids in the high-acid radioactive waste liquid. The wastewater composition and treatment operation are the same as those in Example 1. The CADD inlet and outlet water quality and acid recovery rate are shown in Table 3. The treatment process balance diagram is shown in Figure 6 shown.

[0053] Table 3 CADD inlet and outlet water quality and acid salt recovery rate

[0054]

[0055] The diffusion dialysis unit in this embodiment adopts both anion exchange membrane and cation exchange membrane, making full use of the difference in their ion retention properties, effectively allowing the complex cations and anions of high-acid nuclides with different compositions in different acid concentrations to pass through the membrane for effective separation.

[0056] It can be seen from Table 3 that the UO2(NO3)4 in the original acid and residual acid -2 The complex anion is relatively high, which is consistent with the literature that under acidic conditions above 4N, the complex anion is the main component. -2 Only 0.0009mol / L, which means that under the dual action of the anion and cation exchange membranes of the above diffusion dialysis unit, anions can also show a high interception rate, and its recovery rate is as high as 96%. +2It can also show a very high interception rate, and the recovery rate can be as high as 93.5%, which shows that the diffusion dialysis unit stacking provided in this embodiment can effectively separate ions according to their different interception performances.

[0057] Example 4

[0058] A system for separating nuclides and acids in highly acidic radioactive waste liquid, such as Figure 7 As shown, it is composed of two diffusion dialysis units in Example 3, which are named as the first diffusion dialysis unit 1 and the second diffusion dialysis unit 2. The acid-producing outlet of the first cation exchange membrane diffusion dialysis membrane stack 101 in the first diffusion dialysis unit 1 is connected to the acid inlet of the second cation exchange membrane diffusion dialysis membrane stack 201 of the second diffusion dialysis unit 2 through a pipeline; the residual acid outlet of the second anion exchange membrane diffusion dialysis membrane stack 202 is connected to the raw water inlet of the first anion exchange membrane diffusion dialysis membrane stack 102 through a pipeline, and a circulation pump 4 is installed on the pipeline.

[0059] In this embodiment, the system for separating nuclides and acids adopts both anion exchange membranes and cation exchange membranes, making full use of the different interception properties of their ions, effectively allowing the complex cations and anions of high-acid nuclides with different compositions in different acid concentrations to pass through the membrane for effective separation. At the same time, according to the separation function design of each membrane stack, the side where the liquid flows into the first cation exchange membrane diffusion dialysis membrane stack is the radioactive original acid area, corresponding to H as the high radiation chamber partition; M is the intermediate buffer chamber partition; the side of the second cation exchange membrane stack is the acid production area, corresponding to L as the low radiation chamber partition. The combination of two diffusion dialysis units forms an intermediate buffer zone M as a separation between high-concentration nuclides and low-radiation acid production after acid separation, which can reduce the radiation of nuclides to the external environment, especially the risk of membrane rupture will not have a significant impact on the output acid, and also increase the safety of process operation and maintenance.

[0060] The above system was used to separate nuclides and acids from a high-acid and highly radioactive waste liquid. The treatment results are shown in Table 4.

[0061] Table 4: CACADD inlet and outlet water quality and acid salt recovery rate

[0062]

[0063] It can be seen from Table 4 that the system of this embodiment adopts both the complex anion MNO3 - Content (only 0.009 mol / L), or cationic M ++(only 0.003mol / L), raw water and acid production are low-radiation fluids. As for raw water and raw acid, fluids with high radiation content, there is no direct contact between the two, but indirect contact through an intermediate circulating fluid, which is conducive to radiation protection. Even if some membranes leak due to failure or other reasons, there will be no direct pollution. At the same time, this system also shows a high interception performance of radiation ions, whether it is for complex anions MNO3 - , or complex cation M ++ , and can achieve a recovery rate of more than 97%. This shows that the above system can effectively separate according to the different interception properties of ions, effectively play the advantages of anion diffusion dialysis and cation diffusion dialysis, and has high acid separation efficiency and nuclide separation efficiency.

[0064] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A system for separating nuclides and acids in highly acidic radioactive waste liquid, characterized in that: It comprises at least two connected diffusion dialysis units, wherein the diffusion dialysis unit comprises two connected diffusion dialysis membrane stacks, wherein the diffusion dialysis membrane stack is provided with two groups of partitions, wherein an ion exchange membrane is provided in the middle of the partition, wherein the ion exchange membrane is an anion exchange membrane or a cation exchange membrane, and wherein the diffusion dialysis membrane stack is provided with an acid inlet, a raw water inlet, a residual acid outlet and an acid production outlet; The ion exchange membranes of the two diffusion dialysis membrane stacks are respectively a cation exchange membrane and an anion exchange membrane. The residual acid outlet of the cation exchange membrane diffusion dialysis membrane stack is connected to the acid inlet of the anion exchange membrane diffusion dialysis membrane stack through a pipeline. The raw water inlet of the cation exchange membrane diffusion dialysis membrane stack is connected to the acid production outlet of the anion exchange membrane diffusion dialysis membrane stack through a pipeline. The acid-generating outlet of the cation exchange membrane diffusion dialysis membrane stack of the first diffusion dialysis unit is connected to the acid inlet of the cation exchange membrane diffusion dialysis membrane stack of the second diffusion dialysis unit through a pipeline, and the residual acid outlet of the anion exchange membrane diffusion dialysis membrane stack of the second diffusion dialysis unit is connected to the raw water inlet of the anion exchange membrane diffusion dialysis membrane stack of the first diffusion dialysis unit through a pipeline; The partition is provided with an upper flow port and a lower flow port; An acidity meter is provided on the pipeline connecting the cation exchange membrane diffusion dialysis membrane stack and the anion exchange membrane diffusion dialysis membrane stack; A circulation pump is provided on the pipeline connecting the anion exchange membrane diffusion dialysis membrane stack of the first diffusion dialysis unit and the anion exchange membrane diffusion dialysis membrane stack of the second diffusion dialysis unit.

2. The system for separating nuclides and acids according to claim 1, characterized in that: The diffusion dialysis membrane stack is prepared by screw extrusion or extruder extrusion.

3. The system for separating nuclides and acids according to claim 1, characterized in that: The dimensions of the ion exchange membrane are: 500 mm in width and 200 mm in length.

4. The system for separating nuclides and acids according to claim 1, characterized in that: Each group of the separators is composed of 40 membrane separators, and each membrane separator has a length of 200 mm, a width of 400 mm, and a thickness of 6 mm.

5. The system for separating nuclides and acids according to claim 4, characterized in that: The inner grid thickness of the membrane separator is 5 mm.

Images