Uranium-containing waste residue treatment method

Abstract

The invention belongs to the technical field of uranium waste residue treatment, and aims to solve the problems that uranium-containing waste residues are difficult to completely dissolve, and the radioactivity of raffinate secondary residues is difficult to meet the exempt requirement. The invention provides a uranium-containing waste residue treatment method which comprises the following steps: roasting uranium-containing waste residues at high temperature, removing organic components in the uranium-containing waste residues, activating uranium compounds in the waste residues, completely dissolving the roasted uranium-containing waste residues by using a dissolving agent and adding oxygen to form a dissolving solution, extracting uranium in the dissolving solution through cross-flow extraction, adding ammonia into tail liquid after uranium extraction, precipitating, and drying to obtain uranium-containing waste residues. And the slag becomes exempt secondary slag. According to the method, the solubility of the uranium-containing waste residues is improved through roasting activation, the acid dissolution capacity is enhanced through oxygenation dissolution, and complete leaching of uranium is achieved.

Description

Technical Field

[0001] The present application belongs to the technical field of uranium waste residue treatment, and in particular, relates to a method for treating uranium-containing waste residue. Background Art

[0002] Uranium-containing waste residue refers to solid waste with low uranium content but not meeting emission requirements produced during the uranium conversion and purification process. The main component of uranium-containing waste residue is water-insoluble alkaline hydroxide, in which uranium generally exists in the form of ammonium diuranate, with a uranium content of about 2.0%. Because it contains uranium, it is radioactive and poses a radiation hazard if not treated. If properly treated, the uranium in it can be recovered.

[0003] At present, the method used to deal with uranium-containing waste slag is to temporarily store it in barrels without further processing. This not only poses a radiation hazard, but also fails to recover the uranium in the waste slag.

[0004] The purpose of the Chinese patents, a leaching device for uranium-containing waste residue (CN108257707A) and a leaching method for uranium-containing alkaline slag that is difficult to leach (CN114182115A), is to recover uranium from uranium-containing waste residue. However, due to the low leaching rate, the waste residue after uranium recovery does not meet the exemption emission requirements, and the radioactivity problem of uranium-containing waste residue is not solved. At present, the exemption requirement for radioactive waste residue in the national standard is that the specific activity is less than 1Bq / g. Summary of the invention

[0005] The purpose of the present application is to provide a method for treating uranium-containing waste residue, so as to solve the problem that the uranium-containing waste residue is difficult to completely dissolve and the radioactivity of the secondary residue of the raffinate is difficult to meet the exemption requirements.

[0006] In order to achieve the above objectives, this application provides the following technical solutions:

[0007] In a first aspect, the present application provides a method for treating uranium-containing waste residue, comprising:

[0008] Step 1: roasting the uranium-containing waste slag at high temperature to remove the organic components and activate the uranium compounds in the waste slag;

[0009] Step 2: using a solvent and adding oxygen to completely dissolve the roasted uranium-containing waste residue to form a solution;

[0010] Step 3: extracting uranium from the solution by cross-current extraction;

[0011] Step 4: After uranium extraction, the tail liquid is precipitated with ammonia and dried to become exempted secondary slag.

[0012] In some embodiments, the uranium-containing waste slag is uranium-containing waste slag that can be directly dissolved in nitric acid, uranium-containing waste slag that can be dissolved in nitric acid after roasting, or uranium-containing waste slag that can be dissolved after adding hydrofluoric acid to nitric acid.

[0013] In some embodiments, the uranium-containing waste slag is roasted at a temperature range of 550°C ≤ T ≤ 900°C, and for a time range of 0.5h ≤ t ≤ 5h, while air is introduced to completely remove organic components in the waste slag and activate it into active uranium trioxide powder.

[0014] In some embodiments, the dissolving agent is nitric acid, sulfuric acid, hydrofluoric acid, or hydrochloric acid.

[0015] In some embodiments, during the dissolution of uranium-containing waste slag, the amount of nitric acid added is 10 mol / kg to 15 mol / kg of HNO3 / uranium-containing waste slag.

[0016] In some embodiments, during the dissolution of uranium-containing waste slag, the reaction temperature does not exceed 85° C. and the reaction time is 2 h to 3 h.

[0017] In some embodiments, TBP is used as an extractant for extraction, sulfonated kerosene is used as a diluent, the TBP sulfonated kerosene solution is an organic phase, and the dissolving liquid is an aqueous phase.

[0018] In some embodiments, the TBP concentration in the TBP and sulfonated kerosene solution ranges from 28% to 100%.

[0019] In some embodiments, the acidity of the solvent ranges from 1.5 mol / L to 2.0 mol / L, and the organic phase / aqueous phase flow ratio ranges from 1 to 5.

[0020] In some embodiments, the mass percentage concentration of ammonia water used is 10% to 29%. The pH value of the dissolved solution is first adjusted to 1 to 2 with ammonia water, and then ammonia water is added until the pH value reaches 8 to 9.

[0021] Compared with the prior art, the uranium-containing waste slag treatment method provided in this application has the following beneficial effects:

[0022] The present application improves the solubility of uranium-containing waste slag by roasting and activation, strengthens the acid solubility by adding oxygen for dissolution, and realizes complete leaching of uranium.

[0023] This application completely separates uranium and waste residue through cross-current extraction, reduces the radioactive specific activity of waste residue, and realizes the exemption of uranium-containing waste residue. For example, after processing 1kg of uranium-containing waste residue, the uranium content of the secondary residue obtained is 35ppm (specific activity 0.875Bq / g), which meets the requirements for the specific activity of exemption.

[0024] This application proposes a complete disposal process with a uranium recovery rate of 99% and the specific activity of the treated waste residue is less than 1Bq / g, meeting the requirements for emission exemption. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the technical solution of the present application, the following is a brief introduction to the drawings required for the technical description.

[0026] Figure 1 A flow chart of the method for treating uranium-containing waste slag provided in this application;

[0027] Figure 2 The flow chart of uranium-containing waste slag treatment provided for this application. DETAILED DESCRIPTION

[0028] The following is further explained in detail through specific implementation methods.

[0029] like Figure 1 and Figure 2 As shown, the present application provides a method for treating uranium-containing waste residue, comprising:

[0030] Step 1: roasting the uranium-containing waste slag at high temperature to remove the organic components and activate the uranium compounds in the waste slag;

[0031] Step 2: using a solvent such as nitric acid and adding oxygen to completely dissolve the uranium-containing waste slag after roasting to form a dissolving liquid;

[0032] Step 3: extracting uranium from the solution using cross-current extraction technology;

[0033] Step 4: After deep uranium extraction, the tail liquid is precipitated with ammonia and dried to become exempted secondary slag.

[0034] In step 1, the uranium-containing waste residue is roasted at a high temperature to remove the organic components therein, activate the uranium compounds in the waste residue, improve its solubility, ensure that the solution is clear, and facilitate extraction. The uranium-containing waste residue can be uranium-containing waste residue that can be directly dissolved by nitric acid, or uranium-containing waste residue that can be dissolved by nitric acid after roasting, or uranium-containing waste residue that can be dissolved by adding hydrofluoric acid to nitric acid; and can be uranium-containing waste residue of various abundances.

[0035] In step 1, the uranium-containing waste slag is roasted at a temperature T in the range of 550° C. ≤ T ≤ 900° C., and for a time t in the range of 0.5 h ≤ t ≤ 5 h. Meanwhile, a proper amount of air is introduced to completely remove the organic components in the waste slag and activate it into active uranium trioxide powder.

[0036] In step 2, oxygen is introduced into a dissolving agent such as nitric acid to continuously oxidize the low-valent uranium in the uranium-containing waste slag during the dissolution process, ensuring that the uranium-containing waste slag after roasting is completely dissolved to form a dissolving solution. The dissolving agent can be various acids such as nitric acid, sulfuric acid, hydrofluoric acid, and hydrochloric acid, so that the uranium in the dissolving solution is in the form of uranyl ions.

[0037] During the dissolution of uranium-containing waste slag, the amount of nitric acid added is HNO3 / uranium-containing waste slag (10-15) mol / kg to ensure sufficient acid content.

[0038] During the dissolution of uranium-containing waste slag, the oxygen intake is controlled at >1L / kgU·h to ensure that the oxygen addition amount is sufficient to oxidize the low-valent uranium in the uranium-containing waste slag.

[0039] During the dissolution of uranium-containing waste slag, the reaction temperature is controlled at <85°C.

[0040] During the dissolution of uranium-containing waste slag, the reaction time is controlled at (2.0-3.0) h.

[0041] During the dissolution process of uranium-containing waste slag, physical stirring, such as mechanical stirring, electromagnetic stirring, etc., can be used.

[0042] In step 3, the uranium in the solution is extracted by cross-current extraction technology; TBP is used as an extractant, sulfonated kerosene is used as a diluent, the TBP sulfonated kerosene solution is an organic phase, and the solution is an aqueous phase. Each stage of extraction uses an organic phase without uranium to extract uranium from the aqueous phase, and the uranium in the aqueous phase can be infinitely extracted.

[0043] Various general extraction equipment can be used in the process of uranium extraction.

[0044] During the uranium extraction process, the number of cross-current extraction stages is (3 to 10).

[0045] During the uranium extraction process, the TBP concentration in the TBP+sulfonated kerosene solution ranges from (28 to 100)%.

[0046] During the uranium extraction process, the acidity of the solution is controlled at (1.5-2.0) mol / L.

[0047] During the uranium extraction process, the organic phase / aqueous phase flow ratio ranges from 1 to 5.

[0048] During the uranium extraction process, the temperature is controlled at room temperature.

[0049] In step 4, the tailings after deep uranium extraction are precipitated with ammonia and dried to become exempted secondary slag. The tailings are the dissolved liquid after deep uranium extraction, and the secondary slag is the slag obtained after the tailings are precipitated and dried. The treatment is divided into two processes, namely precipitation and drying.

[0050] During the ammonia precipitation process, the mass percentage concentration of the ammonia water used is controlled at (10-29)%.

[0051] During the ammonia precipitation process, the pH of the dissolved solution is first adjusted to 1-2 with ammonia water, and then ammonia water is added until the pH value reaches 8-9.

[0052] During the ammonia precipitation process, the ammonia addition time after precipitation occurs is controlled to be more than 15 minutes to avoid the precipitation particles being too fine.

[0053] During the ammonia precipitation process, the precipitation temperature is controlled at (65-70)°C.

[0054] During the ammonia precipitation process, physical stirring can be used, such as mechanical stirring, electromagnetic stirring, etc.

[0055] Before the drying process, solid-liquid separation is performed by filtering, centrifuging, etc.

[0056] During the drying process, various heating methods such as microwave, thermal radiation, and heat conduction can be used; various operation methods such as spraying, fluidization, and fixed bed can be used; various general equipment such as converters and fluidized beds can be used.

[0057] During the drying process, the drying temperature is controlled at (120-150)°C.

[0058] During the drying process, the drying time is based on the moisture content of the secondary slag after drying being less than 5%.

[0059] Example

[0060] Take a certain amount of uranium-containing waste slag, roast it at an oxidation temperature of 750°C for 1h, accurately weigh 1000g of the uranium-containing waste slag after roasting and put it into a beaker, slowly add 800ml of 65% nitric acid while stirring, and at the same time, introduce oxygen at a rate of 1L / h. The reaction temperature is controlled below 85°C and dissolved for 2h. If insoluble matter is still found, continue to add nitric acid or hydrofluoric acid until it is completely dissolved.

[0061] After dissolution is completed, let it stand and cool, and adjust the acidity to 1.5 mol / L, as the aqueous phase for extraction. Take 1.2 L TBP and mix it with 2.8 L sulfonated kerosene to make TBP sulfonated kerosene solution, as the organic phase. Take 1 L of the above aqueous phase and organic phase respectively, mix them thoroughly, and then put them into a separatory funnel and stand for stratification. After stratification, collect the uranium-containing organic phase for use, and continue to add 1 L of organic phase to the aqueous phase after stratification to mix thoroughly and stratify. Repeat this cross-current extraction 4 times.

[0062] The collected uranium-containing organic phase is back-extracted to recover the uranium therein, the aqueous phase (tail liquid) after extraction is heated to 65°C, and the pH value is adjusted to 1 with 26% ammonia water under stirring, and ammonia water is continued to be slowly added, and the ammonia addition time is controlled to be more than 15 minutes, and the addition is stopped when the pH value reaches 9 to obtain a solid-liquid mixture. After the solid-liquid mixture is cooled, it is all placed in a Buchner funnel for filtration, and the solid is placed in an oven and dried at 130°C until the moisture content of the solid is less than 5%. The uranium content of the obtained solid submitted for inspection is 35ppm (specific activity 0.875Bq / g), which meets the requirements for the specific activity of exemption from emission and is a secondary slag that can be exempted from emission.

[0063] The present application proposes a method for completely dissolving uranium-containing waste residue, including roasting activation and oxygen dissolution. Since there are some acid-insoluble substances in the uranium-containing waste residue, and the acid-insoluble substances contain a certain amount of uranium, the conventional direct acid dissolution process cannot completely dissolve the uranium-containing waste residue, resulting in part of the uranium being unable to be recycled, and the remaining acid-insoluble substances are still uranium-containing waste residue, which needs further treatment.

[0064] The method couples a high-temperature roasting process before acid dissolution to activate the uranium-containing waste slag and improve its dissolution performance. At the same time, the organic components in the waste slag are removed to ensure that the dissolving solution is not turbid, which is conducive to the extraction of uranium. The low-valent uranium contained in the uranium-containing waste slag is difficult to be completely dissolved by ordinary acid dissolution process. The method adopts oxygen dissolution to convert all uranium ions into hexavalent uranyl ions, so that the uranium-containing waste slag can be completely dissolved and the uranium leaching rate reaches 100%.

[0065] This method is a method for improving the extraction rate and reducing the uranium content in the raffinate tail liquid. In terms of uranium removal efficiency, cross-current extraction is better than countercurrent extraction. This method uses unconventional cross-current extraction. Multiple cross-currents can infinitely reduce the uranium content in the raffinate tail liquid, completely separate uranium from other impurities, and ensure that the slag obtained after precipitation and drying can meet the exemption requirements.

[0066] This application provides a complete disposal process with a uranium recovery rate of over 99%. The specific activity of the treated waste residue is less than 1Bq / g, which meets the requirements for emission exemption and realizes the complete disposal of uranium-containing waste residue.

[0067] The above description is only a specific implementation manner of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily conceived by any technician familiar with the technical field within the technical scope disclosed in the present application should be covered within the protection scope of the present application.

Claims

1. A method for treating uranium-containing waste residue, characterized in that: include: Step 1: roasting the uranium-containing waste slag at high temperature to remove the organic components and activate the uranium compounds in the waste slag; Step 2: using a solvent and adding oxygen to completely dissolve the roasted uranium-containing waste residue to form a solution; Step 3: extracting uranium from the solution by cross-current extraction; Step 4: After uranium extraction, the tail liquid is precipitated with ammonia and dried to become exempted secondary slag.

2. The method for treating uranium-containing waste slag according to claim 1, characterized in that: The uranium-containing waste slag is uranium-containing waste slag that can be directly dissolved by nitric acid, uranium-containing waste slag that can be dissolved by nitric acid after roasting, or uranium-containing waste slag that can be dissolved after adding hydrofluoric acid to nitric acid.

3. The method for treating uranium-containing waste slag according to claim 1, characterized in that: In step 1, the uranium-containing waste slag is roasted at a temperature range of 550° C. ≤ T ≤ 900° C. and a roasting time range of 0.5 h ≤ t ≤ 5 h, and air is introduced at the same time to completely remove organic components in the waste slag and activate it into active uranium trioxide powder.

4. The method for treating uranium-containing waste slag according to claim 1, characterized in that: In step 2, the solvent is nitric acid, sulfuric acid, hydrofluoric acid or hydrochloric acid.

5. The method for treating uranium-containing waste slag according to claim 1, characterized in that: In step 2, during the dissolution of the uranium-containing waste residue, the amount of nitric acid added is 10 mol / kg to 15 mol / kg of HNO3 / uranium-containing waste residue.

6. The method for treating uranium-containing waste slag according to claim 1, characterized in that: In step 2, during the dissolution of the uranium-containing waste slag, the reaction temperature does not exceed 85° C. and the reaction time is 2 h to 3 h.

7. The method for treating uranium-containing waste slag according to claim 1, characterized in that: In step 3, TBP is used as an extractant for extraction, sulfonated kerosene is used as a diluent, the TBP sulfonated kerosene solution is an organic phase, and the dissolving liquid is an aqueous phase.

8. The method for treating uranium-containing waste slag according to claim 7, characterized in that: The TBP concentration range of the TBP and sulfonated kerosene solution is 28% to 100%.

9. The method for treating uranium-containing waste slag according to claim 7, characterized in that: The acidity range of the dissolving solution is 1.5 mol / L to 2.0 mol / L, and the flow ratio range of the organic phase to the aqueous phase is 1 to 5.

10. The method for treating uranium-containing waste slag according to claim 1, characterized in that: In step 4, the mass percentage concentration of ammonia water used is 10% to 29%. The pH value of the dissolved solution is first adjusted to 1 to 2 with ammonia water, and then ammonia water is added until the pH value reaches 8 to 9.

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