Uranium purification method and device

Abstract

The invention discloses a uranium purification method and device, and the method comprises the following steps: (1) extraction: carrying out countercurrent contact mass transfer on a uranium-containing solution to be purified and an organic phase 30% TBP-kerosene in a second single multi-stage centrifugal extractor, and extracting hexavalent uranium in the uranium-containing solution into the organic phase to obtain a uranium-loaded first organic phase and raffinate; washing the first organic phase in a third single multi-stage centrifugal extractor by using a detergent to obtain a uranium-loaded second organic phase and washing residual liquid; the washing raffinate and the uranium-containing solution are combined and then enter a second single multi-stage centrifugal extractor; and (2) reverse extraction: the second organic phase and a reverse extraction agent are subjected to countercurrent contact mass transfer in a fourth single multi-stage centrifugal extractor, hexavalent uranium in the second organic phase enters the water phase through reverse extraction, and thus a purified uranium solution is obtained. The method is simple in step, easy to operate, short in time consumption, compact in device structure, small in occupied area, small in solvent radiolysis effect and capable of meeting different flux requirements.

Description

Technical Field

[0001] The invention relates to the technical field of spent fuel post-processing, and in particular to a uranium purification method and device. Background Art

[0002] The nuclear fuel cycle is an important part of the nuclear industry, and spent fuel reprocessing is one of the key links in realizing the nuclear fuel cycle.

[0003] In the nuclear fuel reprocessing industry, pulse extraction columns, mixing and settling tanks and other liquid-liquid extraction equipment are key equipment in the process flow of spent fuel reprocessing plants. With the development of power reactors and fast neutron breeder reactors, many highly enriched uranium and high burnup spent fuels have appeared in the reprocessing objects. The increase in burnup and fissile material content has brought a series of problems to reprocessing, the most important of which are nuclear criticality safety and solvent irradiation damage.

[0004] At present, uranium purification is mainly achieved by using mixing and settling tanks and supporting facilities, but this method has certain disadvantages and limitations, such as requiring more equipment, introducing additional power sources between adjacent mixing and settling tanks, occupying a large area, high plant investment, and a large amount of waste gas. In addition, the long contact time between the two phases causes the solvent to be irradiated and degraded, resulting in an increase in the waste organic phase. With the rapid development of nuclear power and the increasing requirements for the processing capacity of spent fuel reprocessing, a method and device are urgently needed to solve the above problems. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a uranium purification method and device in view of the above-mentioned deficiencies in the prior art, which has simple steps, is easy to operate, takes up little time, has a compact device structure, occupies a small area, has a small solvent radiolysis effect, and can adapt to different flux requirements.

[0006] The technical solution of the present invention to solve the above technical problems is:

[0007] According to a first aspect of the present invention, there is provided a method for purifying uranium, comprising:

[0008] Step (1) extraction: the uranium-containing solution to be purified is subjected to countercurrent contact mass transfer with an organic phase of 30% TBP-kerosene in a second single multistage centrifugal extractor, so that the hexavalent uranium in the uranium-containing solution is extracted into the organic phase, and a first organic phase loaded with uranium and a raffinate are obtained; the first organic phase is washed with a detergent in a third single multistage centrifugal extractor to purify the impurity nuclides and fragment elements therein, and a second organic phase loaded with uranium and a washing residue are obtained; the washing residue is combined with the uranium-containing solution to be purified, and then the washing residue is introduced into a second single multistage centrifugal extractor together with the organic phase of 30% TBP-kerosene for countercurrent contact mass transfer;

[0009] Step (2) stripping: the second organic phase and the stripping agent are contacted and mass transferred in a fourth single multi-stage centrifugal extractor in countercurrent flow, so that the hexavalent uranium in the second organic phase is stripped into the aqueous phase, thereby obtaining a purified uranium solution.

[0010] Optionally, the extraction in step (1) further comprises:

[0011] The raffinate is washed with kerosene in the first single multi-stage centrifugal extractor to remove the organic phase entrained in the raffinate to obtain a third organic phase, and the third organic phase is combined with 30% TBP-kerosene of the organic phase and then enters the second single multi-stage centrifugal extractor for countercurrent contact and mass transfer with the uranium-containing solution to be purified.

[0012] Optionally, the detergent is a nitric acid solution containing a reducing agent, and its acidity is 1 to 1.5 mol / L.

[0013] Optionally, the reducing agent is hydroxylamine nitrate or dimethylhydroxylamine.

[0014] Optionally, the concentration of the hydroxylamine nitrate is 0.1-0.5 mol / L.

[0015] Optionally, the concentration of the dimethylhydroxylamine is 0.5-1 mol / L.

[0016] Optionally, the volume of the detergent in the extraction of step (1) is 1 / 8 to 1 / 4 of the volume of the first organic phase.

[0017] Optionally, the stripping agent is a nitric acid solution.

[0018] Optionally, the volume flow ratio of 30% TBP-kerosene, uranium-containing solution, detergent and stripping agent in the extraction of step (1) and the stripping of step (2) is 2:1:0.5:1 to 6:3:1:2.

[0019] Optionally, the flow rate of the uranium-containing solution in the extraction in step (1) is in the range of 500 to 1200 L / h.

[0020] Optionally, the first single multistage centrifugal extractor, the second single multistage centrifugal extractor, the third single multistage centrifugal extractor and the fourth single multistage centrifugal extractor are all single multistage centrifugal extractors with 3 to 12 stages.

[0021] Optionally, the residence time of the extraction in step (1) is 2 to 15 seconds, and the residence time of the stripping in step (2) is 2 to 15 seconds.

[0022] According to a second aspect of the present invention, there is provided a uranium purification device, comprising a second single multi-stage centrifugal extractor, a third single multi-stage centrifugal extractor and a fourth single multi-stage centrifugal extractor, wherein:

[0023] The second single multi-stage centrifugal extractor is used for countercurrent contact mass transfer between the uranium-containing solution to be purified and the organic phase 30% TBP-kerosene, so that the hexavalent uranium in the uranium-containing solution is extracted into the organic phase to obtain the first organic phase loaded with uranium and the raffinate;

[0024] The third single multi-stage centrifugal extractor is connected to the second single multi-stage centrifugal extractor, and is used to wash the first organic phase with a detergent to purify the impurity nuclides and fragment elements therein, to obtain a second organic phase loaded with uranium and a washing residue, and to combine the washing residue with the uranium-containing solution to be purified and then conduct countercurrent contact mass transfer with the organic phase 30% TBP-kerosene;

[0025] The fourth single multi-stage centrifugal extractor is connected to the third single multi-stage centrifugal extractor and is used for countercurrent contact and mass transfer between the second organic phase and the stripping agent, so that the hexavalent uranium in the second organic phase is stripped into the aqueous phase, thereby obtaining a purified uranium solution.

[0026] Optionally, the device further comprises a first single multi-stage centrifugal extractor, which is connected to the second single multi-stage centrifugal extractor and is used for washing the raffinate with kerosene to remove the organic phase entrained in the raffinate to obtain a third organic phase, and combining the third organic phase with the organic phase 30% TBP-kerosene for countercurrent contact mass transfer with the uranium-containing solution to be purified.

[0027] Compared with the prior art, the uranium purification method and device of the present invention have the following advantages:

[0028] (1) The steps are simple, easy to operate, and time-saving. Each single multi-stage centrifugal extractor is connected in series for feeding and discharging, does not require an intermediate container, and reduces the number of operating points and instrumentation and control measurement points;

[0029] (2) The uranium extraction and stripping yields are high, up to 99.9%, with high efficiency;

[0030] (3) Wide flux range and large production capacity. The maximum uranium-containing solution flux can reach 1200L / h, which can meet different flux requirements;

[0031] (4) In a single multi-stage centrifugal extractor, the two-phase feed liquid phase separation is fast, the feed liquid residence time is short, and the volume of the retained liquid is small. On the one hand, it can effectively reduce the radiolysis effect of the solvent, that is, the solvent radiolysis effect is small, and on the other hand, it can ensure critical safety;

[0032] (5) This method uses a single multi-stage centrifugal extractor, and through the characteristics of the intermediate stage feed, one device can play different roles. For example, extraction and oil removal can be carried out simultaneously in one device, or different impurity elements can be washed in a targeted manner by using acids of different acidities during the washing process without the need to add additional equipment, thereby reducing equipment investment and making the process simpler and easier to operate.

[0033] (6) Compared with the prior art in which a mixing and settling tank is generally used as an extraction device in the uranium purification cycle, the equipment size of a single multi-stage centrifugal extractor is much smaller than that of a mixing and settling tank with the same processing flux. The device has a compact structure and occupies a small area, which reduces construction investment and has a lower investment. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 Schematic diagram of a uranium purification method and device in an embodiment of the present invention.

[0035] In the figure: 1, the first single multi-stage centrifugal extractor; 2, the second single multi-stage centrifugal extractor; 3, the third single multi-stage centrifugal extractor; 4, the fourth single multi-stage centrifugal extractor. DETAILED DESCRIPTION

[0036] In order to enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention will be clearly and completely described below in conjunction with the drawings in the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work belong to the protection scope of the present invention.

[0037] In view of the fact that the extraction and purification of uranium in the post-processing process of the prior art usually uses a mixing and settling tank as an extraction device, however, the mixing and settling tank has the problems of large floor space and high plant investment, the present invention provides a uranium purification method, comprising:

[0038] Step (1) extraction: the uranium-containing solution to be purified is subjected to countercurrent contact mass transfer with an organic phase of 30% TBP (tributyl phosphate)-kerosene in a second single multi-stage centrifugal extractor, so that the hexavalent uranium in the uranium-containing solution is extracted into the organic phase, and a first organic phase loaded with uranium and a raffinate are obtained; the first organic phase is washed with a detergent in a third single multi-stage centrifugal extractor to purify other impurity nuclides and fragment elements such as plutonium, neptunium, ruthenium, etc., to obtain a second organic phase loaded with uranium and a washing residue; the washing residue is combined with the uranium-containing solution to be purified and then introduced into a second single multi-stage centrifugal extractor together with the organic phase of 30% TBP-kerosene for countercurrent contact mass transfer;

[0039] Step (2) stripping: the second organic phase and the stripping agent are contacted and mass transferred in a fourth single multi-stage centrifugal extractor in countercurrent flow, so that the hexavalent uranium in the second organic phase is stripped into the aqueous phase, thereby obtaining a purified uranium solution.

[0040] Accordingly, the present invention also provides a uranium purification device for the above method, comprising a second single multi-stage centrifugal extractor, a third single multi-stage centrifugal extractor and a fourth single multi-stage centrifugal extractor, wherein:

[0041] The second single multi-stage centrifugal extractor is used for countercurrent contact mass transfer between the uranium-containing solution to be purified and the organic phase 30% TBP-kerosene, so that the hexavalent uranium in the uranium-containing solution is extracted into the organic phase to obtain the first organic phase loaded with uranium and the raffinate;

[0042] The third single multi-stage centrifugal extractor is connected to the second single multi-stage centrifugal extractor, and is used to wash the first organic phase with a detergent to purify the impurity nuclides and fragment elements therein to obtain a second organic phase loaded with uranium and a washing residue, and to combine the washing residue with the uranium-containing solution to be purified and then contact the organic phase 30% TBP-kerosene in countercurrent for mass transfer;

[0043] The fourth single multi-stage centrifugal extractor is connected to the third single multi-stage centrifugal extractor and is used for countercurrent contact mass transfer between the second organic phase and the stripping agent to strip the hexavalent uranium in the second organic phase into the aqueous phase, thereby obtaining a purified uranium solution.

[0044] Example 1

[0045] like Figure 1 As shown, this embodiment discloses a method for purifying uranium, comprising:

[0046] Step (1) extraction: the uranium-containing solution to be purified is subjected to countercurrent contact mass transfer with an organic phase 30% TBP (tributyl phosphate)-kerosene in a second single multistage centrifugal extractor 2, so that the hexavalent uranium in the uranium-containing solution is extracted into the organic phase 30% TBP-kerosene, and the hexavalent uranium is concentrated to obtain a first organic phase loaded with uranium and a raffinate; the first organic phase is washed with a detergent in a third single multistage centrifugal extractor 3 to purify other impurity nuclides and fragment elements such as plutonium, neptunium, ruthenium, etc., to obtain a second organic phase loaded with uranium and a washing residue; the washing residue is combined with the uranium-containing solution to be purified and then introduced into a second single multistage centrifugal extractor 2 together with the organic phase 30% TBP-kerosene for countercurrent contact mass transfer.

[0047] In some embodiments, the detergent is a nitric acid solution containing a reducing agent, and the acidity of the nitric acid solution containing a reducing agent is 1 to 1.5 mol / L. In this concentration range, other fragment elements can be washed cleanly, otherwise other elements may still be entrained, affecting the subsequent stripping process. Specifically, the acidity of the nitric acid solution containing a reducing agent can be 1.1 mol / L, 1.2 mol / L, 1.3 mol / L, 1.4 mol / L, 1.5 mol / L, etc., but is not limited thereto.

[0048] In some embodiments, the reducing agent is hydroxylamine nitrate or dimethylhydroxylamine. These two reducing agents have better reduction effects on impurity elements such as plutonium, neptunium, and ruthenium, and it is difficult to achieve the desired effect using other reducing agents.

[0049] Among them, the concentration of hydroxylamine nitrate is 0.1-0.5 mol / L. In this concentration range, the reduction effect of impurity elements such as plutonium, neptunium, and ruthenium is better, and other concentrations are difficult to achieve the ideal effect. Specifically, the concentration of hydroxylamine nitrate can be 0.1 mol / L, 0.2 mol / L, 0.3 mol / L, 0.4 mol / L, 0.5 mol / L, etc., but not limited to this;

[0050] The concentration of dimethylhydroxylamine is 0.5-1 mol / L. In this concentration range, the reduction effect of impurity elements such as plutonium, neptunium, and ruthenium is better, and other concentrations are difficult to achieve the desired effect. Specifically, the concentration of dimethylhydroxylamine can be 0.5 mol / L, 0.6 mol / L, 0.7 mol / L, 0.8 mol / L, 0.9 mol / L, 1.0 mol / L, etc., but not limited thereto.

[0051] In some embodiments, the volume of the detergent in the extraction of step (1) is 1 / 8 to 1 / 4 of the volume of the first organic phase. In this concentration range, other elements in the fragments can be washed cleanly, otherwise other elements may still be entrained, affecting the subsequent stripping process.

[0052] Step (2) stripping: The second organic phase and the stripping agent are contacted and transferred in countercurrent in the fourth single multi-stage centrifugal extractor 4, so that the hexavalent uranium in the second organic phase is stripped into the aqueous phase, thereby obtaining a purified uranium solution (i.e. Figure 1 The uranium-containing feed liquid concentrate is shown).

[0053] In some embodiments, the stripping agent is a nitric acid solution. The concentration of the nitric acid solution is 0.1 to 1 mol / L. Within this concentration range, uranium can be stripped into the nitric acid solution well. Specifically, the concentration of the nitric acid solution can be 0.1 mol / L, 0.2 mol / L, 0.3 mol / L, 0.4 mol / L, 0.5 mol / L, 0.6 mol / L, 0.7 mol / L, 0.8 mol / L, 0.9 mol / L, 1.0 mol / L, etc., but is not limited thereto.

[0054] In some embodiments, the volume flow ratio of the organic phase 30% TBP-kerosene, the uranium-containing solution, the detergent and the stripping agent in step (1) extraction and step (2) stripping is 2:1:0.5:1 to 6:3:1:2.

[0055] In some embodiments, the flow rate of the uranium-containing solution in the extraction of step (1) is in the range of 500 to 1200 L / h.

[0056] In some embodiments, the extraction in step (1) further comprises: washing and deoiling the raffinate with kerosene in a first single multi-stage centrifugal extractor 1 to remove the organic phase entrained in the raffinate to obtain a third organic phase, combining the third organic phase with the organic phase 30% TBP-kerosene and then entering the second single multi-stage centrifugal extractor 2 for countercurrent contact and mass transfer with the uranium-containing solution to be purified.

[0057] Specifically, if Figure 1 As shown, kerosene is introduced from the organic phase inlet of the first single multistage centrifugal extractor 1, 30% TBP-kerosene is introduced from the organic phase inlet of the second single multistage centrifugal extractor 2, detergent is introduced from the water phase inlet of the third single multistage centrifugal extractor 3, and the uranium-containing solution and the water phase outlet feed liquid (i.e., washing residual liquid) of the third single multistage centrifugal extractor 3 are combined and introduced from the water phase inlet of the second single multistage centrifugal extractor 2. In the extraction step, the organic phase and the aqueous phase are contacted and mass transferred in countercurrent between two centrifugal extractors, so that the hexavalent uranium in the uranium solution is extracted into the organic phase 30% TBP-kerosene, and the hexavalent uranium is concentrated to obtain a first organic phase and a raffinate; after the first organic phase is washed with a detergent (a nitric acid solution containing a reducing agent), other nuclides such as plutonium, neptunium, ruthenium and fragment elements are further purified to obtain a second organic phase and a washing residue, and the second organic phase enters a subsequent stripping step, and the washing residue is combined with the uranium-containing solution to be purified and then contacted and mass transferred with the organic phase 30% TBP-kerosene in countercurrent; after the extracted raffinate is washed and deoiled with kerosene, the organic phase entrained in the raffinate is removed to obtain a third organic phase, and the third organic phase is combined with the organic phase 30% TBP-kerosene and then contacted and mass transferred with the uranium-containing solution to be purified in countercurrent, and the deoiled aqueous phase waste liquid is discharged from the aqueous phase outlet of the first single multi-stage centrifugal extractor.

[0058] The uranium-loaded organic phase (i.e., the second organic phase) produced in step (1) is introduced from the organic phase inlet of the fourth single multi-stage centrifugal extractor 4, and the stripping agent is introduced from the water phase inlet of the fourth single multi-stage centrifugal extractor 4. During the stripping process, the organic phase and the water phase are contacted and mass transferred in countercurrent in the fourth single multi-stage centrifugal extractor, and the hexavalent uranium in the uranium-loaded organic phase 30%-TBP kerosene (i.e., the second organic phase) is stripped into the water phase by the stripping agent, so that the uranium solution is purified and concentrated to obtain a uranium solution, and the organic phase waste liquid after stripping is discharged from the organic phase outlet of the fourth single multi-stage centrifugal extractor.

[0059] In some embodiments, since the first single multi-stage centrifugal extractor, the second single multi-stage centrifugal extractor, the third single multi-stage centrifugal extractor and the fourth single multi-stage centrifugal extractor all adopt a single multi-stage centrifugal extractor, two streams of detergent with different concentrations can be simultaneously introduced at different stages to wash different impurity elements.

[0060] In this embodiment, the number of stages of the first single multi-stage centrifugal extractor, the second single multi-stage centrifugal extractor, the third single multi-stage centrifugal extractor and the fourth single multi-stage centrifugal extractor is preferably 3 to 12. Within this range of the number of stages of the extractors, the effects of extraction and stripping can be better achieved. If the number of extraction stages is too small, it is difficult to fully carry out the extraction and stripping processes.

[0061] In some embodiments, the residence time of the extraction in step (1) is 2 to 15 seconds. Within this residence time range, the two phases can be better in contact and the extraction process can be carried out to achieve the best extraction effect; the residence time of the stripping in step (2) is 2 to 15 seconds. Within this residence time range, the two phases can be better in contact and the stripping process can be carried out to achieve the best extraction effect.

[0062] Compared with the prior art, the uranium purification method of this embodiment has at least the following advantages:

[0063] (1) The steps are simple, easy to operate, and time-saving. Each single multi-stage centrifugal extractor is connected in series for feeding and discharging, does not require an intermediate container, and reduces the number of operating points and instrumentation and control measurement points;

[0064] (2) The uranium extraction and stripping yields are high, up to 99.9%, with high efficiency;

[0065] (3) Wide flux range and large production capacity. The maximum uranium-containing solution flux can reach 1200L / h, which can meet different flux requirements;

[0066] (4) In a single multi-stage centrifugal extractor, the two-phase feed liquid phase separation is fast, the feed liquid residence time is short, and the volume of the retained liquid is small. On the one hand, it can effectively reduce the radiolysis effect of the solvent, that is, the solvent radiolysis effect is small, and on the other hand, it can ensure critical safety;

[0067] (5) This method uses a single multi-stage centrifugal extractor, and through the characteristics of the intermediate stage feed, one device can play different roles. For example, extraction and oil removal can be carried out simultaneously in one device, or different impurity elements can be washed in a targeted manner by using acids of different acidities during the washing process without the need to add additional equipment, thereby reducing equipment investment and making the process simpler and easier to operate.

[0068] (6) Compared with the prior art in which a mixing and settling tank is generally used as an extraction device in the uranium purification cycle, the equipment size of a single multi-stage centrifugal extractor is much smaller than that of a mixing and settling tank with the same processing flux. The device has a compact structure and occupies a small area, which reduces construction investment and has a lower investment.

[0069] Example 2

[0070] like Figure 1 As shown, this embodiment discloses a uranium purification device, which is used in the above-mentioned uranium purification method, comprising a second single multi-stage centrifugal extractor 2, a third single multi-stage centrifugal extractor 3 and a fourth single multi-stage centrifugal extractor 4, wherein:

[0071] The second single multi-stage centrifugal extractor 2 is used for countercurrent contact mass transfer between the uranium-containing solution to be purified and the organic phase 30% TBP-kerosene, so that the hexavalent uranium in the uranium-containing solution is extracted into the organic phase to obtain the first organic phase loaded with uranium and the raffinate;

[0072] The third single multi-stage centrifugal extractor 3 is connected to the second single multi-stage centrifugal extractor 2, and is used to wash the first organic phase with a detergent to purify the impurity nuclides and fragment elements therein, to obtain a second organic phase loaded with uranium and a washing residue, and to combine the washing residue with the uranium-containing solution to be purified and then conduct countercurrent contact mass transfer with the organic phase 30% TBP-kerosene;

[0073] The fourth single multi-stage centrifugal extractor 4 is connected to the third single multi-stage centrifugal extractor 3 and is used for countercurrent contact mass transfer between the second organic phase and the stripping agent to strip the hexavalent uranium in the second organic phase into the aqueous phase, thereby obtaining a purified uranium solution.

[0074] In some embodiments, the device of this embodiment further comprises a first single multi-stage centrifugal extractor 1, which is connected to a second single multi-stage centrifugal extractor 2, and is used for washing the raffinate with kerosene to remove the organic phase entrained in the raffinate to obtain a third organic phase, and combining the third organic phase with the organic phase 30% TBP-kerosene and then contacting the uranium-containing solution to be purified in countercurrent mass transfer.

[0075] The working process of the uranium purification device of this embodiment is described in detail below, which is as follows:

[0076] Kerosene is introduced from the organic phase inlet of the first single multistage centrifugal extractor 1, 30% TBP-kerosene is introduced from the organic phase inlet of the second single multistage centrifugal extractor 2, detergent is introduced from the water phase inlet of the third single multistage centrifugal extractor 3, and the uranium-containing solution is introduced from the water phase inlet of the second single multistage centrifugal extractor 2, and the organic phase and the water phase are contacted and mass transferred in countercurrent between the two centrifugal extractors, so that the hexavalent uranium in the uranium solution is extracted into the organic phase 30% TBP-kerosene, and the hexavalent uranium is concentrated to obtain a first organic phase and a raffinate; the first organic phase is treated with a detergent (a nitric acid solution containing a reducing agent) ) after washing, further purifying other nuclides and fragment elements such as plutonium, neptunium, ruthenium, etc. to obtain a second organic phase and a washing residue, the second organic phase enters a subsequent stripping step, the washing residue is combined with the uranium-containing solution to be purified and then contacted with the organic phase 30% TBP-kerosene in countercurrent for mass transfer; the raffinate after extraction is washed with kerosene for oil removal, and the organic phase entrained in the raffinate is removed to obtain a third organic phase, the third organic phase is combined with the uranium-containing solution to be purified and then contacted with the organic phase 30% TBP-kerosene in countercurrent for mass transfer, and the deoiled aqueous phase waste liquid is discharged from the aqueous phase outlet of the first single multi-stage centrifugal extractor 1.

[0077] The uranium-loaded organic phase (i.e., the second organic phase) produced in step (1) is introduced from the organic phase inlet of the fourth single multi-stage centrifugal extractor 4, and the stripping agent is introduced from the water phase inlet of the fourth single multi-stage centrifugal extractor 4. The organic phase and the water phase are contacted and mass transferred in countercurrent in the fourth centrifugal extractor, and the stripping agent strips the hexavalent uranium in the uranium-loaded organic phase 30%-TBP kerosene (i.e., the second organic phase) into the water phase, thereby purifying and concentrating the uranium solution to obtain a uranium solution. The organic phase waste liquid after stripping is discharged from the organic phase outlet of the fourth single multi-stage centrifugal extractor.

[0078] Example 3

[0079] like Figure 1 As shown, this embodiment discloses a method for uranium purification, which has the same steps as the method described in Example 1, except that:

[0080] The uranium solubility in the uranium-containing solution to be purified is 3.5 g / L and the acid concentration is 2 mol / L;

[0081] The detergent is a nitric acid solution containing hydroxylamine nitrate, wherein the concentration of hydroxylamine nitrate is 0.2 mol / L;

[0082] The stripping agent is 1 mol / L nitric acid solution;

[0083] The flow rate of the uranium-containing solution was 1000 L / h, and the volume flow ratio of the organic phase 30% TBP-kerosene, the uranium-containing solution, the detergent, and the nitric stripping agent was 2:1:1:1;

[0084] The number of stages of each single multi-stage centrifugal extractor in step (1) extraction and step (2) stripping is 8.

[0085] According to Figure 1 The process shown in the figure sequentially performs countercurrent extraction, washing and stripping on the uranium-containing feed liquid, removes oil from the raffinate, and finally obtains a uranium-containing feed liquid concentrate (i.e., a purified uranium solution). The results are as follows: under the process conditions, the uranium extraction yield is greater than 99.9%, the stripping yield is greater than 99.9%, and the uranium concentration after concentration is 31 g / L, which is significantly higher than the initial uranium concentration of 3.5 g / L. It can be seen that this method can achieve a good uranium purification effect.

[0086] Example 4

[0087] like Figure 1 As shown, this embodiment discloses a method for uranium purification, which has substantially the same steps as the method described in Example 3, except that:

[0088] The flow rate of the uranium-containing solution is 700 L / h.

[0089] The results are as follows: under the process conditions, the uranium extraction yield is greater than 99.9%, the stripping yield is greater than 99.9%, and the uranium concentration after enrichment is 31.5 g / L. Compared with Example 3, the uranium concentration after enrichment in this embodiment is improved. It can be seen that appropriately reducing the flow rate of the uranium-containing solution is beneficial to further improve the uranium purification effect.

[0090] Example 5

[0091] like Figure 1 As shown, this embodiment discloses a method for uranium purification, which has substantially the same steps as the method described in Example 3, except that:

[0092] The detergent is a nitric acid solution containing dimethylhydroxylamine, wherein the concentration of the dimethylhydroxylamine is 0.5 mol / L.

[0093] The results are as follows: under the process conditions, the uranium extraction yield is greater than 99.9%, the stripping yield is greater than 99.9%, and the uranium concentration after enrichment is 33.2 g / L, which is significantly higher than the initial uranium concentration of 3.5 g / L. It can be seen that this method can achieve a good uranium purification effect.

[0094] Example 6

[0095] like Figure 1 As shown, this embodiment discloses a method for uranium purification, which has substantially the same steps as the method described in Example 3, except that:

[0096] The detergent is a nitric acid solution containing hydroxylamine nitrate, wherein the concentration of hydroxylamine nitrate is 0.5 mol / L.

[0097] The results are as follows: under the process conditions, the uranium extraction yield is greater than 99.9%, the stripping yield is greater than 99.9%, and the uranium concentration after enrichment is 32.5 g / L. Compared with Example 3, the uranium concentration after enrichment in this embodiment is improved. It can be seen that appropriately increasing the concentration of the reducing agent is beneficial to further improving the uranium purification effect.

[0098] Example 7

[0099] like Figure 1 As shown, this embodiment discloses a method for uranium purification, which has substantially the same steps as the method described in Example 3, except that:

[0100] The number of stages of each single multi-stage centrifugal extractor in step (1) extraction and step (2) stripping is 5.

[0101] The results are as follows: under the process conditions, the uranium extraction yield is greater than 99.9%, the stripping yield is greater than 99.9%, and the uranium concentration after enrichment is 30.3 g / L. Compared with Example 3, the uranium concentration after enrichment in this example is reduced. It can be seen that appropriately increasing the number of centrifugal extractors is beneficial to further improve the uranium purification effect.

[0102] It is to be understood that the above embodiments are merely exemplary embodiments used to illustrate the principles of the present invention, but the present invention is not limited thereto. For those of ordinary skill in the art, various modifications and improvements can be made without departing from the spirit and essence of the present invention, and these modifications and improvements are also considered to be within the scope of protection of the present invention.

Claims

1. A method for purifying uranium, characterized in that: include: Step (1) extraction: the uranium-containing solution to be purified is contacted with 30% TBP-kerosene in an organic phase in a second single multi-stage centrifugal extractor for countercurrent mass transfer, so that the hexavalent uranium in the uranium-containing solution is extracted into the organic phase to obtain a first organic phase loaded with uranium and a raffinate; washing the first organic phase with a washing agent in a third single multi-stage centrifugal extractor to purify the impurity nuclides and fragment elements therein, thereby obtaining a second organic phase loaded with uranium and a washing residue; The washing residue is combined with the uranium-containing solution to be purified and then enters into a second single multi-stage centrifugal extractor for countercurrent contact mass transfer with the organic phase 30% TBP-kerosene; Step (2) stripping: the second organic phase and the stripping agent are contacted and mass transferred in a fourth single multi-stage centrifugal extractor in countercurrent flow, so that the hexavalent uranium in the second organic phase is stripped into the aqueous phase, thereby obtaining a purified uranium solution.

2. The method for purifying uranium according to claim 1, characterized in that: The extraction step (1) further comprises: The raffinate is washed with kerosene in the first single multi-stage centrifugal extractor to remove the organic phase entrained in the raffinate to obtain a third organic phase, and the third organic phase is combined with 30% TBP-kerosene of the organic phase and then enters the second single multi-stage centrifugal extractor for countercurrent contact and mass transfer with the uranium-containing solution to be purified.

3. The method for purifying uranium according to claim 1 or 2, characterized in that: The detergent is a nitric acid solution containing a reducing agent, and its acidity is 1-1.5 mol / L.

4. The method for purifying uranium according to claim 3, characterized in that: The reducing agent is hydroxylamine nitrate or dimethylhydroxylamine.

5. The method for purifying uranium according to claim 4, characterized in that: The concentration of the hydroxylamine nitrate is 0.1-0.5 mol / L.

6. The method for purifying uranium according to claim 4, characterized in that: The concentration of the dimethylhydroxylamine is 0.5-1 mol / L.

7. The method for purifying uranium according to claim 3, characterized in that: The volume of the detergent in the extraction of step (1) is 1 / 8 to 1 / 4 of the volume of the first organic phase.

8. The method for purifying uranium according to claim 3, characterized in that: The stripping agent is a nitric acid solution.

9. The method for purifying uranium according to claim 8, characterized in that: The volume flow ratio of 30% TBP-kerosene, uranium-containing solution, detergent and stripping agent in the extraction of step (1) and stripping of step (2) is 2:1:0.5:1-6:3:1:

2.

10. The method for purifying uranium according to claim 9, characterized in that: The flow rate of the uranium-containing solution in the extraction of step (1) is in the range of 500 to 1200 L / h.

11. The method for purifying uranium according to claim 1 or 2, characterized in that: The first single multistage centrifugal extractor, the second single multistage centrifugal extractor, the third single multistage centrifugal extractor and the fourth single multistage centrifugal extractor are all single multistage centrifugal extractors with 3 to 12 stages.

12. The method for purifying uranium according to claim 1 or 2, characterized in that: The residence time of the extraction in step (1) is 2 to 15 seconds, and the residence time of the stripping in step (2) is 2 to 15 seconds.

13. A uranium purification device, characterized in that: It includes a second single multi-stage centrifugal extractor, a third single multi-stage centrifugal extractor and a fourth single multi-stage centrifugal extractor, wherein: The second single multi-stage centrifugal extractor is used for countercurrent contact mass transfer between the uranium-containing solution to be purified and the organic phase 30% TBP-kerosene, so that the hexavalent uranium in the uranium-containing solution is extracted into the organic phase to obtain the first organic phase loaded with uranium and the raffinate; The third single multi-stage centrifugal extractor is connected to the second single multi-stage centrifugal extractor, and is used to wash the first organic phase with a detergent to purify the impurity nuclides and fragment elements therein, to obtain a second organic phase loaded with uranium and a washing residue, and to combine the washing residue with the uranium-containing solution to be purified and then conduct countercurrent contact mass transfer with the organic phase 30% TBP-kerosene; The fourth single multi-stage centrifugal extractor is connected to the third single multi-stage centrifugal extractor and is used for countercurrent contact and mass transfer between the second organic phase and the stripping agent, so that the hexavalent uranium in the second organic phase is stripped into the aqueous phase, thereby obtaining a purified uranium solution.

14. The uranium purification device according to claim 13, characterized in that: Also included is the first single multi-stage centrifugal extractor, The first single multi-stage centrifugal extractor is connected to the second single multi-stage centrifugal extractor to wash the raffinate with kerosene to remove the organic phase entrained in the raffinate to obtain a third organic phase, and the third organic phase is combined with the organic phase 30% TBP-kerosene and then subjected to countercurrent contact mass transfer with the uranium-containing solution to be purified.

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