Method for preparing uranium product from uranyl carbonate solution through catalytic hydrogenation reduction

Abstract

The invention relates to the technical field of uranium product preparation, and particularly discloses a method for preparing a uranium product from a uranyl carbonate solution through catalytic hydrogenation reduction, and the method comprises the following steps: (1) uranyl carbonate pretreatment; (2) performing catalytic hydrogenation reduction on uranium in the raw material liquid; (3) hydrolytic precipitation of tetravalent uranium; and (4) filtering the precipitate slurry and drying the product. On the basis of the uranyl carbonate solution catalytic hydrogenation reduction theory, hydrogenation reduction of hexavalent uranium and hydrolytic precipitation of tetravalent uranium are separately carried out, hydrogenation reduction of hexavalent uranium adopts nickel powder with high catalytic activity, precious metal loaded with platinum and palladium and other catalysts, efficient and rapid reduction can be achieved through a stirring kettle or fixed bed equipment, and the method is simple and convenient to operate. According to the method, materials entering and exiting a catalytic reactor exist in a liquid form by controlling blending of a uranyl carbonate stock solution, reduction conditions and the like, automatic control and stable operation are facilitated, the obtained tetravalent uranium solution is heated, hydrolyzed and precipitated under the normal pressure condition, and the whole process is simple in equipment and high in operability.

Description

Technical Field

[0001] This application relates to the field of uranium product preparation technology, specifically to a method for preparing uranium products from uranyl carbonate solution by catalytic hydrogenation reduction. Background Technology

[0002] Uranium can be precipitated from alkaline uranyl carbonate solution using direct sodium hydroxide precipitation. However, due to the strong complexation ability of carbonate ions with uranium, complete precipitation is difficult. To achieve high precipitation efficiency, excess sodium hydroxide is usually added, resulting in high alkali consumption during precipitation and making it difficult to recycle the mother liquor. For uranyl carbonate solutions with high uranium concentrations, a certain amount of acid can be added first to acidify and remove carbonate ions, followed by adding alkali to adjust the pH to around 7 to precipitate uranium. However, this method requires a large amount of acid solution for carbonate removal, leading to significant acid and alkali consumption. Furthermore, both methods yield sodium diuranate, which has a low uranium content, resulting in high storage and transportation costs.

[0003] Therefore, for the current methods of preparing uranium products from alkaline uranyl carbonate solutions, it is necessary to develop more economical and efficient processing techniques to reduce reagent consumption, improve the recycling rate of process water, and thus enhance economic and environmental benefits. To this end, our previously filed patent, "A Method for Preparing Uranium Oxide Products from Alkaline Qualified Uranium Solution" (202211172907.7), discloses a process for preparing uranium products from alkaline qualified uranium solution. This method uses the generated uranium oxide as a catalyst to prepare a slurry with a uranium oxide content of 100-1000 g / L. This slurry is continuously added to a multi-stage reaction vessel system via a metering pump. Through a hydrogen reduction reaction, uranium precipitates as uranium oxide. The resulting slurry is continuously discharged through a self-controlled valve. Part of the slurry is returned to prepare the raw material slurry, while the rest is filtered, dried, and used to obtain uranium oxide products for storage. This invention features a simple process, low reagent consumption, and high-quality precipitated uranium products, effectively solving the problems of high chemical reagent consumption, large wastewater treatment volume, and high uranium product transportation costs in current alkaline qualified uranium solution precipitation processes in my country. However, this method uses uranium oxide as the catalyst, which has poor catalytic effect. To obtain satisfactory catalytic performance, a large amount of uranium oxide is required as the catalyst. On the one hand, a large amount of uranium precipitate is returned to prepare the raw material slurry, resulting in low overall equipment processing efficiency. On the other hand, the high solids content of the raw material slurry is prone to deposition in the equipment and pipelines, causing blockages and affecting the continuous and stable operation of the process. This places high demands on the equipment and its supporting control system, making industrial implementation difficult. If a higher-performance catalyst, such as nickel powder or precious metal catalyst, is used for hydrogenation reduction under the above process conditions, although the amount of catalyst used can be greatly reduced, facilitating stable and continuous operation of the equipment, the precipitate is a mixture of uranium product and catalyst, which is difficult to separate subsequently, and it is difficult to obtain high-quality uranium product.

[0004] In the process of developing this application, the applicant discovered that the relevant technology has at least the following problems: Currently, there is no economical, efficient, environmentally friendly, and easy-to-operate uranium precipitation process, either domestically or internationally. Based on current research, this study aims to conduct innovative research on key process conditions and parameters to further develop new methods for uranium precipitation using uranyl carbonate solutions. Summary of the Invention

[0005] In view of this, this application provides a method for preparing uranium products from uranyl carbonate solution by catalytic hydrogenation reduction. The main purpose is to solve the problems of high chemical reagent consumption, low process water recycling rate, low uranium content of the obtained uranium product, high product storage and transportation costs, and heavy economic and environmental pressure on uranium water treatment plants by conventional methods for precipitating uranium from alkaline uranyl carbonate solution. The new hydrogenation reduction method has the problems of high operating temperature, high labor intensity, and difficulty in solving process bottlenecks such as continuous and stable operation.

[0006] To achieve the above objectives, this application provides a method for preparing uranium products from uranyl carbonate solution by catalytic hydrogenation reduction, the method comprising the following steps: (1) Pretreatment: Uranyl carbonate solution with uranium concentration ≤20g / L and pH=6-7 was used as raw material solution; (2) Catalytic hydrogenation reduction of uranium: The pretreated feed liquid is added to the catalytic hydrogenation reactor for catalytic hydrogenation reduction. The reaction temperature is 10-20℃ and the reaction time is 10-30min. (3) Hydrolysis precipitation of tetravalent uranium: Heat the solution obtained in step (2) to 60-100℃ and stir for 1-3 hours to hydrolyze and precipitate to obtain a slurry; (4) Precipitated slurry filtration and product drying: The slurry described in step (3) is filtered, and the resulting filter cake is dried and crushed to obtain uranium oxide product.

[0007] In some embodiments, the alkaline uranyl carbonate solution in step (1) includes alkaline carbonate leaching solution from uranium ore, alkaline carbonate washing solution from uranium mine, and / or qualified alkaline carbonate back-extraction solution from uranium mine.

[0008] In some embodiments, the alkaline uranyl carbonate solution comprises uranium, carbonate ions, and bicarbonate ions.

[0009] In some embodiments, the concentration of uranium is 0.2-50 g / L, and the total concentration of carbonate ions and bicarbonate ions is 5-60 g / L.

[0010] In some embodiments, when the uranium concentration of the uranyl carbonate solution is >20 g / L in step (1), the uranium concentration is adjusted to ≤20 g / L by precipitation or dilution.

[0011] In some embodiments, step (1) is performed by adding carbon dioxide to the uranyl carbonate solution to make its pH 6-7.

[0012] In some embodiments, the catalytic hydrogenation reactor in step (2) is a high-pressure reactor and / or a fixed-bed catalytic reactor.

[0013] In some embodiments, the catalyst used for catalytic hydrogenation reduction in step (2) is nickel powder and / or a noble metal catalyst supported on platinum and palladium.

[0014] In some embodiments, the amount of catalyst used in the high-pressure reactor is 2-15% of the feed liquid; the amount of catalyst filling in the fixed-bed catalytic reactor is ≥50% of the bed volume, and the hydrogen pressure is 0.5-10 MPa.

[0015] In some embodiments, the uranium oxide product in step (4) is tetravalent uranium.

[0016] Compared with existing technologies, the method for preparing uranium products from uranyl carbonate solution by catalytic hydrogenation reduction described in this application has the following advantages: This application separates the catalytic hydrogenation reduction process of uranyl carbonate and the hydrolysis precipitation process of the reduced tetravalent uranium. This achieves selective reduction and precipitation of uranium in solution, obtaining high-quality uranium oxide products, while avoiding the bottleneck problem of simultaneous uranium reduction and precipitation. This develops a method for preparing uranium products by hydrogenation reduction of alkaline uranyl carbonate solution with simple equipment, simple operation, and low cost.

[0017] The uranium oxide product obtained by the method of this application meets the requirements of the uranium ore concentrate standard GB / T10268-2008. The uranium concentration in the mother liquor after precipitation can be reduced to below 0.2 g / L, and it can be recycled as a carbonate solution to prepare leaching agent, washing agent or back-extraction agent. Attached Figure Description

[0018] Various other advantages and benefits will become apparent to those skilled in the art upon reading the following detailed description of preferred embodiments. The accompanying drawings are for illustrative purposes only and are not intended to limit the scope of this application. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings: Figure 1 This illustration shows a schematic diagram of a process for preparing uranium products from uranyl carbonate solution by catalytic hydrogenation reduction according to an embodiment of this application. Detailed Implementation

[0019] As the background technology shows, traditional alkaline precipitation processes for uranium product preparation suffer from problems such as high chemical reagent consumption and low process water recycling rate. Existing hydrogen reduction methods require relatively high temperatures, and uranium reduction and precipitation occur simultaneously. Using efficient catalysts presents problems such as difficulty in separating the precipitated uranium product from the catalyst mixture and difficulty in meeting the required uranium product quality. Using the generated uranium product as a catalyst for autocatalytic reaction presents challenges such as large uranium product return, high solids content in the raw material slurry, severe equipment and pipeline blockage, and difficulty in stable operation.

[0020] This application discloses a method for preparing uranium products from uranyl carbonate solution by catalytic hydrogenation reduction. Based on the theory of catalytic hydrogenation reduction of uranyl carbonate solution, the hydrogenation reduction of hexavalent uranium and the hydrolysis precipitation of tetravalent uranium are carried out separately. The hydrogenation reduction of hexavalent uranium uses highly catalytically active catalysts such as nickel powder, platinum, and palladium supported on noble metals, and a catalytic hydrogenation reactor is used to achieve efficient and rapid reduction. By adjusting the uranyl carbonate stock solution and controlling the reduction conditions, the materials entering and leaving the catalytic hydrogenation reactor are in liquid form, which facilitates automated control and stable operation. The resulting tetravalent uranium solution is heated and hydrolyzed under normal pressure to precipitate. The entire process equipment is simple and highly operable.

[0021] For ρ(U)=0.2-50g / L, ρ(CO3 2- +HCO3 - This application first prepares a uranyl carbonate solution with a concentration of 5-60 g / L. Based on the composition of the raw material solution, the solution is adjusted to pH 6-7 and ρ(U) ≤ 20 g / L through carbonation treatment, precipitation mother liquor, or water dilution. The raw material solution and hydrogen are then introduced into a high-pressure reactor or fixed-bed catalytic reactor containing highly active nickel powder or a noble metal catalyst. The reaction temperature is controlled at 10-20℃, and the reaction time is controlled at 10-30 min. The reduction efficiency of hexavalent uranium is ≥ 99%, yielding a tetravalent uranium solution. The obtained tetravalent uranium solution is heated to 60-100℃ and stirred for 1-3 hours. The uranium oxide product obtained by hydrolysis and precipitation is tetravalent uranium. Solid uranium oxide product is obtained by filtration and drying. The product standard meets the requirements of the uranium ore concentrate standard GB / T 10268-2008. The uranium concentration in the mother liquor after precipitation is ≤ 0.2 g / L, which can be recycled as a carbonate solution to prepare leaching agents, washing agents, or back-extraction agents.

[0022] The embodiments of this application are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this application, and should not be construed as limiting this application.

[0023] In this application, the reference to "embodiment" means that a specific feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor is it a mutually exclusive, independent, or alternative embodiment. Those skilled in the art will explicitly and implicitly understand that the embodiments described herein can be combined with other embodiments.

[0024] Those skilled in the art will understand that, unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains. It should also be understood that terms such as those defined in general dictionaries should be understood to have the same meaning as in the context of the prior art, and should not be interpreted in an idealized or overly formal sense unless specifically defined as herein.

[0025] It should be understood that the term "and / or" as used herein is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A alone, A and B simultaneously, and B alone. Additionally, the character " / " in this document generally indicates that the preceding and following related objects have an "or" relationship. The singular forms "a," "the," and "the" are also intended to include the plural forms unless the context clearly indicates otherwise.

[0026] like Figure 1 The method for preparing uranium products from uranyl carbonate solution by catalytic hydrogenation reduction includes the following steps: (1) Pretreatment: A uranyl carbonate solution with a uranium concentration ≤20g / L and pH=6-7 is used as the raw material. Carbon dioxide is introduced into the uranyl carbonate solution, which is alkaline. The pH of the uranyl carbonate solution is adjusted to 6-7. The alkaline uranyl carbonate solution includes alkaline carbonate leaching solution from uranium ore, alkaline carbonate washing solution from uranium mine, and qualified alkaline carbonate back-extraction solution from uranium mine. The main components of the alkaline uranyl carbonate solution are uranium, carbonate ions, and bicarbonate ions. The concentration of uranium is 0.2-50g / L, and the total concentration of carbonate and bicarbonate is 5-60g / L. If necessary, the uranium concentration is controlled to ≤20g / L by using the precipitate mother liquor or water dilution in conjunction with the process. Finally, a uranyl carbonate solution with pH=6-7 and ρ(U)≦20g / L is obtained as the raw material. Controlling the uranium concentration and pH range in the raw material solution can effectively avoid the hydrolysis and precipitation of tetravalent uranium during the next catalytic hydrogenation reduction process.

[0027] (2) Catalytic hydrogenation reduction of uranium: The pretreated feed solution is added to a catalytic hydrogenation reactor at a reaction temperature of 10-20℃ for 10-30 min. The catalytic hydrogenation reactor is a high-pressure reactor or a fixed-bed catalytic reactor. By controlling the reaction temperature and reaction time, the reduction of uranium in the feed solution can be precisely controlled. Specifically, a reaction temperature ≤20℃ can reduce hexavalent uranium in uranyl carbonate to obtain a tetravalent uranium carbonate solution.

[0028] The high-pressure reactor is a batch-operated catalytic hydrogenation reactor. By adding pretreated feed liquid and catalyst to the high-pressure reactor, introducing hydrogen gas, and stirring, efficient catalytic reduction of uranium in the feed liquid is achieved. The amount of catalyst added is 2-15% of the mass of the feed liquid. The reaction temperature is controlled at 10-20℃, and the reaction time is controlled at 10-30 minutes. Strict control of the reaction temperature and time is to ensure efficient uranium reduction during the catalytic hydrogenation process, while avoiding hydrolysis of tetravalent uranium during reduction, ultimately achieving a catalytic hydrogenation reduction efficiency of ≥99% for hexavalent uranium.

[0029] The fixed-bed catalytic reactor is a continuous catalytic hydrogenation reactor. A catalyst is packed into the fixed-bed reactor, and the feed liquid and hydrogen are introduced into the reactor at a certain flow rate. After residence in the fixed-bed catalytic reactor for a period of time, the hydrogen flows out, achieving efficient catalytic reduction of uranium in the feed liquid. Specifically, the catalyst loading in the fixed-bed catalytic reactor is ≥50% of the bed volume, the hydrogen pressure is 0.5-10.0 MPa, the reaction temperature is controlled at 10-20℃, and the residence time in the fixed-bed catalytic reactor is controlled at 10-30 min, ultimately achieving a catalytic hydrogenation reduction efficiency of ≥99% for hexavalent uranium. Strict control of the reaction temperature and reaction time is to ensure efficient reduction of hexavalent uranium during the catalytic hydrogenation reduction of uranium, while avoiding hydrolysis of tetravalent uranium during the reduction process.

[0030] (3) Hydrolysis and precipitation of tetravalent uranium: The solution obtained in step (2) is heated to 60-100℃ and stirred for 1-3 hours to hydrolyze and precipitate a slurry. The slurry is a carbonate solution of tetravalent uranium. During the heating process, some bicarbonate ions in the solution decompose, and at the same time, the tetravalent uranium in the solution undergoes hydrolysis and precipitation to obtain a slurry containing uranium oxide.

[0031] (4) Filtration and drying: The slurry described in step (3) is filtered, and the resulting filter cake is dried and crushed to obtain uranium oxide products. Specifically, the slurry containing uranium oxides is filtered to obtain filter cake and precipitate mother liquor. The filter cake is dried and crushed to obtain uranium oxide products, the quality of which meets the requirements of the uranium ore concentrate standard GB / T 10268-2008. The obtained precipitate mother liquor is returned to the process as a carbonate solution to prepare leaching solution, washing agent or back-extraction agent, etc. for recycling. The uranium concentration in the precipitate mother liquor can be reduced to ≤0.2g / L.

[0032] Example 1 The uranium carbonate leaching solution used in the uranium mine has a main composition of ρ(U) = 19 g / L and pH = 7.86. First, the leaching solution is passed through a carbonation device to absorb carbon dioxide. After carbonation, the solution has a pH of 6.83, and this solution is used as the feed solution.

[0033] The raw material liquid was fed into a stirred tank reactor. Carbonyl nickel powder catalyst was added to the stirred tank at a rate of 10% of the mass of the raw material liquid. Hydrogen gas was introduced at a pressure of 1.5 MPa and a temperature of 18°C. The mixture was stirred for 25 minutes and allowed to stand for 5 minutes. The supernatant obtained from the reduction was then removed from the reactor.

[0034] The above clear liquid was added to a stirred tank and heated to 95°C. The mixture was stirred and reacted for 2.5 hours to hydrolyze and precipitate tetravalent uranium. After filtration, the uranium concentration in the precipitate mother liquor was reduced to 98 mg / L. The filter cake was dried to obtain uranium oxide product, the quality of which met the requirements of the uranium ore concentrate standard GB / T10268-2008.

[0035] Example 2 The qualified alkaline sodium carbonate back-extraction solution used in the uranium mine has a main composition of ρ(U) = 15 g / L and pH = 9.16. First, the qualified back-extraction solution is passed through a carbonation device to absorb carbon dioxide. After carbonation, the solution has a pH of 6.77, and this solution is used as the feed solution.

[0036] The feed liquid was fed into a fixed-bed catalytic reactor, and a supported platinum catalyst was added to the reactor. The catalyst filling amount in the bed was 60%. Hydrogen gas was introduced at a pressure of 2.0 MPa and a temperature of 15°C. The residence time was 15 min. The feed liquid was continuously fed into and out of the fixed-bed catalytic reactor.

[0037] The solution from the fixed-bed catalytic reactor is added to a stirred tank and heated to 95°C. The mixture is stirred for 2.0 h to hydrolyze and precipitate tetravalent uranium. After filtration, the uranium concentration in the precipitate mother liquor is reduced to 76 mg / L. The filter cake is dried to obtain uranium oxide product, the quality of which meets the requirements of the uranium ore concentrate standard GB / T10268-2008.

[0038] Example 3 The uranium carbonate leaching solution used in the uranium mine has a main composition of ρ(U) = 30 g / L and pH = 7.26. First, a certain amount of process water is added to dilute the leaching solution, and carbon dioxide is absorbed through a carbonation device. After treatment, the uranium concentration in the solution is 18 g / L and the pH is 6.91. This solution is then used as the feed solution.

[0039] The raw material liquid was fed into a stirred tank reactor. Carbonyl nickel powder catalyst was added to the stirred tank at a rate of 12% of the mass of the raw material liquid. Hydrogen gas was introduced at a pressure of 1.5 MPa and a temperature of 16°C. The mixture was stirred for 25 minutes and allowed to stand for 5 minutes. The supernatant obtained from the reduction was then removed from the reactor.

[0040] Add the above clear liquid to a stirred tank and heat to 95°C. Stir and react for 2.5 hours to hydrolyze and precipitate tetravalent uranium. Filter the solution and reduce the uranium concentration in the precipitate mother liquor to 88 mg / L. Dry the filter cake to obtain the uranium oxide product, which meets the requirements of the uranium ore concentrate standard GB / T10268-2008.

[0041] Those skilled in the art will understand that the steps, measures, and solutions in the various operations, methods, and processes discussed in this application can be alternated, modified, combined, or deleted. Furthermore, other steps, measures, and solutions in the various operations, methods, and processes discussed in this application can also be alternated, modified, rearranged, decomposed, combined, or deleted. Furthermore, steps, measures, and solutions in the prior art that are similar to those disclosed in this application can also be alternated, modified, rearranged, decomposed, combined, or deleted.

[0042] The above description is only a partial embodiment of this application. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of this application, and these improvements and modifications should also be considered within the scope of protection of this application.

Claims

1. A method for preparing uranium products from uranyl carbonate solution by catalytic hydrogenation reduction, characterized in that, Includes the following steps: (1) Pretreatment: Uranyl carbonate solution with uranium concentration ≤20g / L and pH=6-7 was used as raw material solution; (2) Catalytic hydrogenation reduction of uranium: The pretreated raw material liquid is added to the catalytic hydrogenation reactor for catalytic hydrogenation reduction. The reaction temperature is 10-20℃ and the reaction time is 10-30min. (3) Hydrolysis precipitation of tetravalent uranium: Heat the solution obtained in step (2) to 60-100℃ and stir for 1-3 hours to hydrolyze and precipitate to obtain a slurry; (4) Filtration and drying: The slurry described in step (3) is filtered, and the resulting filter cake is dried and crushed to obtain uranium oxide products.

2. The method for preparing uranium products from uranyl carbonate solution by catalytic hydrogenation reduction according to claim 1, characterized in that, The uranyl carbonate solution in step (1) includes uranium ore alkaline carbonate leaching solution, uranium ore alkaline carbonate washing solution and / or uranium ore alkaline carbonate back-extraction qualified solution.

3. The method for preparing uranium products from uranyl carbonate solution by catalytic hydrogenation reduction according to claim 2, characterized in that, The composition of the uranyl carbonate solution includes uranium, carbonate ions, and bicarbonate ions.

4. The method for preparing uranium products from uranyl carbonate solution by catalytic hydrogenation reduction according to claim 3, characterized in that, The concentration of uranium is 0.2-50 g / L, and the total concentration of carbonate ions and bicarbonate ions is 5-60 g / L.

5. The method for preparing uranium products from uranyl carbonate solution by catalytic hydrogenation reduction according to claim 1, characterized in that, In step (1), when the uranium concentration of the uranyl carbonate solution is >20 g / L, the uranium concentration is adjusted to ≤20 g / L by precipitation or dilution.

6. The method for preparing uranium products from uranyl carbonate solution by catalytic hydrogenation reduction according to claim 1, characterized in that, Step (1) involves adding carbon dioxide to the uranyl carbonate solution to bring its pH to 6-7.

7. The method for preparing uranium products from uranyl carbonate solution by catalytic hydrogenation reduction according to claim 1, characterized in that, The catalytic hydrogenation reactor in step (2) is a high-pressure reactor or a fixed-bed catalytic reactor.

8. The method for preparing uranium products from uranyl carbonate solution by catalytic hydrogenation reduction according to claim 1, characterized in that, The catalyst used in step (2) for catalytic hydrogenation reduction is nickel powder and / or a noble metal catalyst supported on platinum and palladium.

9. The method for preparing uranium products from uranyl carbonate solution by catalytic hydrogenation reduction according to claim 7, characterized in that, The catalyst dosage in the high-pressure reactor is 2-15% of the feed liquid; the catalyst filling amount in the fixed-bed catalytic reactor is ≥50% of the bed volume, and the hydrogen pressure is 0.5-10.0 MPa.

10. The method for preparing uranium products from uranyl carbonate solution by catalytic hydrogenation reduction according to claim 1, characterized in that, The uranium oxide product mentioned in step (4) is tetravalent uranium.

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