Method for treating radioactive TBP / OK organic waste liquid

Abstract

The application discloses a radioactive TBP / OK organic waste liquid treatment method, which comprises the following steps: S1, pretreating radioactive TBP / OK organic waste liquid; S2, alkali washing the pretreated radioactive TBP / OK organic waste liquid; S3, adding a catalyst into the alkali washed radioactive TBP / OK organic waste liquid and pyrolyzing the radioactive TBP / OK organic waste liquid, so that the radioactive TBP / OK organic waste liquid is decomposed into pyrolysis gas and reaction residue; recovering radioactive substances in the reaction residue; S4, condensing the pyrolysis gas after filtering through a high-temperature gas filter, and recovering phosphoric acid, butanol and kerosene gas in the pyrolysis gas; and adding a catalyst into the remaining pyrolysis gas to generate carbon dioxide and water through catalytic combustion. The application has the advantages of high radioactive organic waste liquid treatment efficiency, high recovery efficiency, less waste, addition of the catalyst in the pyrolysis and catalytic combustion processes, reduced pyrolysis and catalytic combustion required temperatures, reduced heat loss, and energy saving and environmental protection.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of radioactive waste treatment, in particular to a method for treating radioactive TBP / OK organic waste liquid. BACKGROUND

[0002] At present, TBP / OK system is mostly used in China for the extraction purification of uranium, plutonium and other elements in uranium purification and spent fuel reprocessing. The extractant is degraded by chemical and irradiation effects due to multiple uses, and its performance becomes poor, and finally becomes radioactive organic phase, i.e. radioactive organic waste liquid.

[0003] At present, there are many studies on the formation mechanism of radioactive TBP / OK, but there are few reports on its treatment method. Among them, the commonly used or more studied methods for treating radioactive TBP / OK are mainly pyrolysis incineration and Fenton oxidation.

[0004] (1) Pyrolysis incineration technology: taking thermal decomposition and gas combustion as the mechanism, two-stage and multi-stage combustion methods are used for incineration. The first stage combustion is to make the waste fully burn under insufficient air, and to decompose the products conducive to further combustion. The second stage combustion is to realize the complete combustion of waste under excess air. The process flow of waste organic phase pyrolysis mainly includes four processes of emulsion preparation, pyrolysis, combustion and waste gas treatment. The tail gas produced by the traditional pyrolysis process is less, and the operation temperature is lower (500-600℃), the secondary waste is less, and the volume reduction ratio is high. However, it still has certain limitations. The reaction rate of pyrolysis process is slow, and the equipment used for incineration is easy to be corroded, and the construction cost of the equipment is high.

[0005] (2) Fenton oxidation method: a relatively mild reaction temperature and pH value are set, and the inorganic treatment of organic phase is realized by adjusting the amount and adding method of oxidizing agent. The principle of oxidation process is shown in Figure 1 At present, Fenton oxidation of radioactive TBP / OK has been studied by various countries, and Fenton method for treating TBP / OK has also been studied by Tsinghua University Nuclear Research Institute, China Institute of Atomic Energy and China Institute of Radiation Protection. The results show that Fenton oxidation can effectively decompose TBP / OK, HDBP / OK solution and interface material. Fenton oxidation method has high efficiency in oxidizing and degrading TBP, and the reaction conditions are simple and the technology is mature. However, it must be carried out in a strong oxidation environment, and the material requirements for equipment containers are high, the construction cost is large, the service life of main equipment is short, in addition, the residue liquid after oxidation also needs further concentration and solidification treatment, and the comprehensive volume reduction effect is not obvious.

[0006] In recent years, in order to treat radioactive TBP / OK waste liquid, researchers have made a lot of exploratory work, and patent CN113643837A discloses a radioactive TBP / OK organic waste liquid mineralization-oxidation treatment process, but because TBP is not pretreated to remove impurities, the volume of waste is large; and the solid product formed after phosphorus solidification and nuclear reaction residue are treated as radioactive solid waste, increasing the amount of waste treatment. Patent CN113571223A discloses a method and device for treating radioactive organic extractant, and the device is fixed and only suitable for treating a large amount of radioactive waste liquid generated in the production line. For treating a small amount of radioactive waste liquid, the device construction cost is too high. SUMMARY

[0007] The purpose of the present application is to overcome the shortcomings of the prior art and provide a radioactive TBP / OK organic waste liquid treatment method, which has high treatment efficiency, safe operation, low energy consumption and high economic benefit.

[0008] To achieve the above purpose, the technical scheme adopted by the present application is as follows:

[0009] A radioactive TBP / OK organic waste liquid treatment method, comprising the following steps:

[0010] S1: Pretreating radioactive TBP / OK organic waste liquid to remove solid impurities;

[0011] S2: Alkaline washing the pretreated radioactive TBP / OK organic waste liquid to remove the interface dirt mixed therein;

[0012] S3: Adding a catalyst to the alkaline washed radioactive TBP / OK organic waste liquid and pyrolyzing, the radioactive TBP / OK organic waste liquid is decomposed into pyrolysis gas and reaction residue by pyrolysis; recovering radioactive substances in the reaction residue;

[0013] S4: The pyrolysis gas generated in step S3 is filtered through a high-temperature gas filter and then condensed, and the phosphoric acid, butanol and kerosene gas in the pyrolysis gas are recovered; the remaining pyrolysis gas is introduced into a catalytic combustion device and added with a catalyst for catalytic combustion to generate carbon dioxide and water, which is filtered through a nuclear grade high-efficiency filter and discharged.

[0014] Further, the volume ratio of TBP in the radioactive TBP / OK organic waste liquid in step S1 is 20% to 60%.

[0015] Further, the pretreatment method in step S1 is to filter the radioactive TBP / OK organic waste liquid with a metal wire mesh to remove larger solid particles in the radioactive TBP / OK organic waste liquid, and then naturally settle for 1 day, so that the radioactive TBP / OK organic waste liquid is divided into three layers, i.e. an oil layer, an oil-water emulsion layer, and water and impurities, and the middle and upper layers of liquid are taken to obtain the pretreated radioactive TBP / OK organic waste liquid.

[0016] Further, the solution for alkaline cleaning in step S2 is one of a sodium carbonate solution, a sodium hydroxide solution, and a calcium hydroxide solution; and the interface dirt in step S2 is generated by insoluble solid micro-particles in the TBP / OK organic waste liquid in the uranium purification and spent fuel reprocessing extraction process.

[0017] Further, the catalyst added in step S3 is one of active alumina, iron oxide, and HZSM-5, and the pyrolysis process is carried out in a negative pressure state and protected by nitrogen, and the required pyrolysis temperature is 100-200 DEG C.

[0018] Further, the radioactive substances in the reaction residue are recovered by using the PUREX process in step S3.

[0019] Further, the catalyst added in step S4 is also one of active alumina, iron oxide, and HZSM-5, and the temperature for catalytic combustion is 250-500 DEG C, and air is introduced into the catalytic combustion device during the catalytic combustion.

[0020] Compared with the prior art, the present application has the following beneficial effects:

[0021] (1) In the present application, the macromolecular structure organic matter is pyrolyzed into pyrolysis gas and reaction residue, and the recovery rate of radioactive substances in the reaction residue is as high as 99%, the pyrolysis gas includes combustible gas, phosphoric acid, kerosene gas, butanol, and water vapor, among which the phosphoric acid, butanol, and kerosene gas in the pyrolysis gas can be recovered by condensation, and the remaining pyrolysis gas is introduced into a catalytic combustion device to make the combustible gas fully burn to generate carbon dioxide and water, and the final products of carbon dioxide and water are filtered by a nuclear grade high-efficiency filter and then discharged into the atmosphere, so that the present application has high radioactive organic waste liquid treatment efficiency, high recovery efficiency, and less waste after treatment of the organic waste liquid.

[0022] (2) In the present application, a catalyst is added in the pyrolysis process, and the required pyrolysis temperature is controlled at 100-200 DEG C, which is 20% of the pyrolysis temperature under normal pressure, so that the heat loss is small, energy saving and environmental protection are achieved, the requirement for equipment is low, and the equipment investment cost is small compared with the direct incineration method.

[0023] (3) The catalytic combustion process of the present application adds a catalyst, and the catalytic combustion temperature is controlled at 250-500 DEG C, the combustion temperature is low, the combustion process is controllable and uniform and stable.

[0024] (4) The collected phosphoric acid can be used as a decontaminant, and the reaction residue generated by pyrolysis can be used to recover uranium, plutonium and other radioactive substances by the PUREX process, thereby achieving waste minimization. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 A schematic diagram of the Fenton oxidation process in the background art of the present application;

[0026] Figure 2 A process flow diagram of the present application. DETAILED DESCRIPTION

[0027] The present application will be further described below in conjunction with the accompanying drawings and examples, and the modes of the present application include but are not limited to the following examples.

[0028] Example 1

[0029] As shown in the figure, the present embodiment provides a method for treating radioactive TBP / OK organic waste liquid, comprising the following steps: Figure 2 S1: Take 10 mL of radioactive TBP / OK organic waste liquid with a TBP content of 20%, filter the radioactive TBP / OK organic waste liquid using a metal wire mesh to remove larger solid particles in the organic waste liquid, and then naturally settle for 1 day, after which the organic waste liquid will be divided into three layers, the upper layer is an oil layer without impurities, the middle layer is an oil-water emulsion layer, and the bottom layer is water and impurities. After removing the water and impurities in the lower layer, the middle and upper layer liquid left is the treated radioactive TBP / OK organic waste liquid;

[0030] S2: Wash the pretreated radioactive TBP / OK organic waste liquid with sodium carbonate alkali to remove the interface contaminants mixed therein; the interface contaminants are generated by the insoluble solid micro-particles in the TBP / OK organic waste liquid during uranium purification and spent fuel reprocessing extraction process, and by radiation or reprocessing of the feed liquid;

[0031] S3: Put the alkali-washed radioactive TBP / OK organic waste liquid into a pyrolysis furnace, add a catalyst, activated alumina, for pyrolysis, the catalyst dosage is 5 wt.% of the TBP / OK organic waste liquid, maintain negative pressure, and increase the temperature to a final temperature of 140 DEG C at a heating rate of 10 DEG C / min, and keep the temperature constant for 60 min to ensure that the organic waste liquid pyrolysis reaction is completed, and the radioactive organic waste liquid is decomposed into pyrolysis gas and reaction residue;

[0032]

[0033] ​S4: The pyrolysis gas is filtered by a high-temperature gas filter to remove radioactive particles and aerosols entrained in the pyrolysis gas, and the filtered pyrolysis gas is subjected to stepwise condensation to recover butanol, phosphoric acid and kerosene gas, and the remaining pyrolysis gas component is combustible gas butene, which is introduced into a catalytic combustion device to be catalytically combusted by adding a catalyst active alumina, so that butene generates water and carbon dioxide, and the combustion temperature is controlled at 320°C, in order to make butene fully combusted, the butene needs to stay in the catalytic combustion device for more than 2s, and a large amount of air needs to be introduced for combustion and to avoid the temperature rise of the combustion furnace;

[0034] S5: The reaction residues generated in step S3 are subjected to extraction by a PUREX process to recover uranium, plutonium and other nuclides therein, and the recovery rate reaches 99%;

[0035] S6: The carbon dioxide and water generated by catalytic combustion in step S4 are filtered by a nuclear-grade high-efficiency filter and discharged into the atmosphere through a chimney.

[0036] The radioactive TBP / OK organic waste liquid treatment method provided in the embodiment can remove the mixed impurities and interface dirt after pretreatment and alkali washing of the TBP / OK organic waste liquid with a TBP content of 20%, and then the TBP / OK organic waste liquid is subjected to catalytic pyrolysis, and the weight loss rate of the TBP / OK organic waste liquid is 98.38%; in addition, the recovery rate of uranium and plutonium in the reaction residues in the pyrolysis furnace reaches 99%; the pyrolysis gas generated can remove more than 90% of radioactive particles and aerosols through a high-temperature gas filter; the pyrolysis gas can recover phosphoric acid, butanol and kerosene gas in the system through condensation, wherein the recovery rate of phosphoric acid reaches 100%, the recovery rate of butanol reaches 98%, and the kerosene gas can be combusted to generate carbon dioxide and water, which is discharged into the atmosphere after detection; the remaining pyrolysis gas component is butene, which is combusted to generate harmless carbon dioxide and water after catalytic combustion, and then filtered by a nuclear-grade high-efficiency filter and discharged.

[0037] Example Two

[0038] Based on example one, the TBP content in the radioactive TBP / OK organic waste liquid can also be 30%, the final temperature for pyrolysis in step S3 can also be 160°C, the temperature for catalytic combustion in step S4 can also be 320°C, and the catalyst added for pyrolysis and catalytic combustion can also be iron oxide.

[0039] The embodiment provides a radioactive TBP / OK organic waste liquid treatment method, after pretreatment and alkali washing of TBP / OK organic waste liquid with 30% TBP content, impurities and interface dirt mixed in can be removed, and then the TBP / OK organic waste liquid is subjected to catalytic pyrolysis, the weight loss rate of the TBP / OK organic waste liquid is 97.52%; in addition, the recovery rate of uranium and plutonium in the reaction residue in the pyrolysis furnace reaches 99%; more than 90% of radioactive particles and aerosols in the generated pyrolysis gas can be removed through a high-temperature gas filter; the pyrolysis gas is condensed to recover phosphoric acid, butanol and kerosene gas in the system, wherein the recovery rate of the phosphoric acid reaches 100%, the recovery rate of the butanol reaches 99%, and the kerosene gas can be combusted to generate carbon dioxide and water, which are discharged into the atmosphere after reaching the standard through detection; the remaining pyrolysis gas component is butene, the butene is subjected to catalytic combustion to generate harmless carbon dioxide and water, and then is discharged after being filtered through a nuclear-grade high-efficiency filter.

[0040] Embodiment three

[0041] Based on the embodiment one, the TBP content in the radioactive TBP / OK organic waste liquid can also be 40%, the final temperature of pyrolysis in the step S3 can also be 180 DEG C, the temperature of catalytic combustion in the step S4 can also be 380 DEG C, and the added catalyst for pyrolysis and catalytic combustion can also be HZSM-5.

[0042] The embodiment provides a radioactive TBP / OK organic waste liquid treatment method, after pretreatment and alkali washing of TBP / OK organic waste liquid with 40% TBP content, impurities and interface dirt mixed in can be removed, and then the TBP / OK organic waste liquid is subjected to catalytic pyrolysis, the weight loss rate of the TBP / OK organic waste liquid is 95.92%; in addition, the recovery rate of uranium and plutonium in the reaction residue in the pyrolysis furnace reaches 99%; more than 90% of radioactive particles and aerosols in the generated pyrolysis gas can be removed through a high-temperature gas filter; the pyrolysis gas is condensed to recover phosphoric acid, butanol and kerosene gas in the system, wherein the recovery rate of the phosphoric acid reaches 100%, the recovery rate of the butanol reaches 99%, and the kerosene gas can be combusted to generate carbon dioxide and water, which are discharged into the atmosphere after reaching the standard through detection; the remaining pyrolysis gas component is butene, the butene is subjected to catalytic combustion to generate harmless carbon dioxide and water, and then is discharged after being filtered through a nuclear-grade high-efficiency filter.

[0043] The reaction conditions and treatment results of the embodiments one, two and three are shown in Table 1.

[0044] Table 1

[0045]

[0046] From the examples one, two and three, it can be seen that the radioactive TBP / OK organic waste liquid is treated by the method provided by the application, after pyrolysis, the recovery rate of radioactive substances uranium and plutonium in the reaction residue is as high as 99%, the recovery rate of phosphoric acid is 100%, the recovery rate of butanol is as high as 98%-99%, and the kerosene gas and butene can be fully combusted into carbon dioxide and water and then discharged into the atmosphere, the method provided by the application has high treatment efficiency and high waste recovery rate, the pyrolysis temperature and the catalytic combustion temperature are relatively low, energy consumption can be effectively reduced, and the method is more energy-saving and environment-friendly.

[0047] The above examples are only one of the preferred embodiments of the application and should not be used to limit the protection scope of the application, but any modification or polishing without substantial meaning made within the main design idea and spirit of the application, the technical problems solved are still consistent with the application, and should be included in the protection scope of the application.

Claims

1. A method for treating radioactive TBP / OK organic waste liquid, characterized in that, The method comprises the following steps: S1: pretreating the radioactive TBP / OK organic waste liquid to remove solid impurities: filtering the radioactive TBP / OK organic waste liquid with a metal wire mesh to remove larger solid particles in the radioactive TBP / OK organic waste liquid, and then naturally settling for 1 day, so that the radioactive TBP / OK organic waste liquid is divided into three layers, i.e. an oil layer, an oil-water emulsion layer, and water and impurities, and the middle and upper layers of liquid are taken as the pretreated radioactive TBP / OK organic waste liquid; S2: alkali washing the pretreated radioactive TBP / OK organic waste liquid to remove interface contaminants mixed therein; S3: adding a catalyst to the alkali washed radioactive TBP / OK organic waste liquid and pyrolyzing, the catalyst is used in an amount of 5wt.% of the TBP / OK organic waste liquid, the radioactive TBP / OK organic waste liquid is decomposed into pyrolysis gas and reaction residues by pyrolysis; radioactive substances in the reaction residues are recovered; the pyrolysis process is carried out in a negative pressure state and protected by nitrogen, and the temperature is raised to 100-200℃ at a rate of 10℃ / min, and the temperature is kept constant for 60min; S4: condensing the pyrolysis gas generated in step S3 after filtering through a high-temperature gas filter, and recovering phosphoric acid, butanol and kerosene gas in the pyrolysis gas; the remaining pyrolysis gas component is combustible gas butene, which is introduced into a catalytic combustion device and added with a catalyst to generate carbon dioxide and water at 250-500℃; the butene stays in the catalytic combustion device for more than 2s, and a large amount of air is introduced for combustion during the combustion process to avoid the temperature rise of the combustion furnace; the generated carbon dioxide and water are filtered through a nuclear-grade high-efficiency filter and discharged.

2. The method for treating radioactive TBP / OK organic waste liquid according to claim 1, characterized in that, The volume ratio of TBP in the radioactive TBP / OK organic waste liquid in step S1 is 20% to 60%.

3. The method for treating radioactive TBP / OK organic waste liquid according to claim 2, characterized in that, The solution used for alkali washing in step S2 is one of a sodium carbonate solution, a sodium hydroxide solution and a calcium hydroxide solution; and the interface contaminants in step S2 are insoluble solid micro-particles generated by irradiation or post-treatment of TBP / OK organic waste liquid in the processes of uranium purification and spent fuel reprocessing.

4. The method for treating radioactive TBP / OK organic waste liquid according to claim 3, characterized in that, The catalyst added in step S3 is one of active alumina, iron oxide and HZSM-5.

5. The method for treating radioactive TBP / OK organic waste liquid according to claim 4, characterized in that, The radioactive substances in the reaction residues are recovered by the PUREX process extraction in step S3.

6. The method for treating radioactive TBP / OK organic waste liquid according to claim 5, characterized in that, The catalyst added in step S4 is also one of active alumina, iron oxide and HZSM-5, and air is introduced into the catalytic combustion device during catalytic combustion.

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