Method and system for treating nitric acid system waste liquid from uranium purification and conversion

Abstract

The present invention provides a method and system for treating a nitric acid system waste liquid from uranium purification and conversion. The method comprises: pretreating a uranium purification waste liquid to obtain a first treated liquid; carrying out an extraction treatment on the first treated liquid to recover uranium from the first treated liquid, to obtain a second treated liquid; carrying out oil removal on the second treated liquid to remove organic matters from the second treated liquid, to obtain a third treated liquid; carrying out evaporation concentration on the third treated liquid to obtain a fourth treated liquid; and carrying out a membrane treatment on the fourth treated liquid to obtain clear freshwater and then discharging the fresh clearwater. In the solution of the present invention, a process route in which various waste liquid treatment methods are used in combination is used, so that an organic combination of the various waste liquid treatment methods is achieved, thereby effectively reducing the content of uranium in a uranium-containing waste liquid, so as to satisfy the discharge standard that the uranium content [U] in a final discharged waste liquid is less than or equal to 50 μg / L.

Description

A method and system for treating waste liquid from a uranium purification and conversion nitric acid system Technical Field

[0001] The present invention relates to the technical field of uranium purification and conversion, in particular to a method and system for treating waste liquid in a uranium purification and conversion nitric acid system. Background Art

[0002] The uranium purification process produces wastewater such as distillation residue and organic phase alkaline wash. Since the raw material for uranium purification is uranium trioxide produced in the uranium mining and smelting system, this uranium trioxide inevitably contains some insoluble impurity particles, and therefore some of these insoluble impurities enter the wastewater. Nitric acid and organic solvents are used in the uranium purification process, so the uranium purification wastewater will contain nitric acid, organic solvents, and other substances, and thus these wastewaters will also contain nitric acid and organic phases.

[0003] According to environmental protection requirements, wastewater generated by uranium purification and conversion production lines must be treated to a uranium content of ≤50μg / L before discharge. However, existing wastewater treatment technologies lack the ability to separate wastewater treatment processes, suffer from low automation levels, fragmented facility layouts, and low technical standards. If the current process continues, the resulting wastewater will not meet emission standards. Furthermore, existing wastewater treatment technologies, which rely on alkaline precipitation for uranium recovery, produce uranium-containing precipitates that are difficult to recycle due to the high level of impurities. Summary of the Invention

[0004] The present invention provides a method and system for treating waste liquid from a uranium purification and conversion nitric acid system, so as to solve the problem that the uranium purification waste liquid cannot meet the emission standards and the recovered uranium contains a large amount of impurities.

[0005] In order to solve the above technical problems, the technical solutions of the present invention are as follows:

[0006] A method for treating waste liquid from a uranium purification and conversion nitric acid system, comprising:

[0007] pre-treating the uranium purification waste liquid to obtain a first treated liquid;

[0008] performing an extraction treatment on the first treatment liquid to recover uranium in the first treatment liquid to obtain a second treatment liquid;

[0009] Degreasing the second treatment liquid to remove organic matter in the second treatment liquid to obtain a third treatment liquid;

[0010] Evaporating and concentrating the third treatment liquid to obtain a fourth treatment liquid;

[0011] The fourth treated liquid is subjected to membrane treatment to obtain a fresh water clear liquid and then discharged.

[0012] Optionally, the uranium purification waste liquid includes at least one of the following:

[0013] Nitric acid distillation residue;

[0014] Organic phase alkaline washing solution;

[0015] Denitrification tail gas eluent;

[0016] Hydrogen reduction bubbling water.

[0017] Optionally, pre-treating the uranium purification waste liquid to obtain a first treated liquid includes:

[0018] A flocculant is added to the uranium purification waste liquid to precipitate insoluble solid impurities in the uranium purification waste liquid and separate them from the uranium purification waste liquid to obtain a first treated liquid.

[0019] Optionally, performing an extraction treatment on the first treatment liquid to recover uranium in the first treatment liquid to obtain a second treatment liquid includes:

[0020] extracting the first treatment liquid with a first extractant at a first preset flow ratio, transferring uranium in the first treatment liquid from the uranium in the aqueous phase to the organic phase, thereby obtaining a loaded organic phase;

[0021] At a first preset temperature, the loaded organic phase is stripped with a second extractant at a second flow ratio, and uranium in the loaded organic phase is recovered in the form of a stripping solution to obtain a second treated solution.

[0022] Optionally, degreasing the second treatment liquid to remove organic matter in the second treatment liquid to obtain a third treatment liquid comprises:

[0023] Inputting the second treatment liquid into an oil removal tower to remove insoluble organic matter in the second treatment liquid;

[0024] The second treatment liquid is subjected to electrocatalytic oxidation treatment to remove soluble organic matter in the second treatment liquid to obtain a third treatment liquid.

[0025] Optionally, evaporating and concentrating the third treatment liquid to obtain the fourth treatment liquid comprises:

[0026] At a second preset temperature, evaporating and separating the fourth treatment liquid to obtain a concentrated liquid;

[0027] At a third preset temperature and a preset vacuum degree, the concentrated liquid is evaporated and crystallized to remove salt, thereby obtaining salt crystals and the fourth treatment liquid.

[0028] Optionally, the fourth treated liquid is subjected to membrane treatment to obtain a fresh water clear liquid and then discharged, comprising:

[0029] The fourth treatment liquid is filtered through an ultrafiltration membrane to remove uranium molecules in the fourth treatment liquid to obtain a first filtrate.

[0030] Optionally, the method for treating uranium purification waste liquid further comprises:

[0031] The first filtrate is filtered through a nanofiltration membrane to remove impurities with a diameter greater than a preset length in the first filtrate to obtain a second filtrate.

[0032] Optionally, the method for treating uranium purification waste liquid further comprises:

[0033] The second filtrate is passed through a reverse osmosis membrane to remove salt particles in the second filtrate, thereby obtaining a fresh water clear liquid with a uranium content of ≤50 μg / L, and discharging the fresh water clear liquid.

[0034] The present invention also provides a waste liquid treatment system for a uranium purification and conversion into nitric acid system, comprising:

[0035] Sequentially connected waste liquid receiving device, oil removal resin tower, extraction device, stripping device, oil-water separation tower, oil removal system, evaporation system, membrane treatment system and discharge tank;

[0036] an organic phase purification system in communication with the stripping device;

[0037] a reagent preparation system in communication with the extraction device;

[0038] The oil removal system includes an electrocatalytic oxidation device and a filter press connected to the electrocatalytic oxidation device;

[0039] The evaporation system includes a multi-effect evaporation system and a single-effect evaporation system connected to the multi-effect evaporation system;

[0040] The membrane treatment system includes an ultrafiltration system, a nanofiltration system and a reverse osmosis system which are connected in sequence;

[0041] The waste liquid receiving device pre-treats the uranium purification waste liquid to obtain a first treated liquid;

[0042] The first treatment liquid is input into an extraction device and a stripping device, and the first treatment liquid is subjected to extraction treatment to recover uranium in the first treatment liquid to obtain a second treatment liquid;

[0043] The second treatment liquid is input into the oil removal system, and the oil is removed from the second treatment liquid to remove organic matter in the second treatment liquid to obtain a third treatment liquid;

[0044] The third treatment liquid is input into the evaporation system, and the third treatment liquid is evaporated and concentrated to obtain a fourth treatment liquid;

[0045] The fourth treated liquid is input into the membrane treatment system, and the fourth treated liquid is subjected to membrane filtration treatment to obtain a fresh water clear liquid, which is then discharged into a discharge tank.

[0046] The above solution of the present invention includes at least the following beneficial effects:

[0047] The above-mentioned solution of the present invention includes: pre-treating uranium purification wastewater to obtain a first treatment liquid; extracting the first treatment liquid to recover uranium from the first treatment liquid to obtain a second treatment liquid; degreasing the second treatment liquid to remove organic matter from the second treatment liquid to obtain a third treatment liquid; evaporating and concentrating the third treatment liquid to obtain a fourth treatment liquid; and membrane treating the fourth treatment liquid to obtain a fresh water clear liquid for discharge. The solution of the present invention utilizes a process route that combines multiple wastewater treatment methods, fully leveraging the advantages of each wastewater treatment method and achieving an organic combination of multiple wastewater treatment methods. This can effectively reduce the uranium content in the uranium-containing wastewater and achieve the final discharge standard of [U] ≤ 50 μg / L. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] 1 is a flow chart of a method for treating waste liquid from a uranium purification and conversion nitric acid system according to an embodiment of the present invention;

[0049] FIG2 is a schematic diagram of a process flow for treating waste liquid from a uranium purification and conversion nitric acid system according to an embodiment of the present invention;

[0050] FIG3 is a schematic diagram of a waste liquid treatment system for a uranium purification and conversion into nitric acid system provided by an embodiment of the present invention.

[0051] Description of reference numerals:

[0052] 1. Waste liquid receiving device; 2. Oil removal resin tower; 31. Extraction device; 32. Stripping device; 33. Organic phase purification system; 34. Reagent preparation system; 4. Oil-water separation tower; 5. Oil removal system; 61. Multi-effect evaporation system; 62. Single-effect evaporation system; 71. Ultrafiltration system; 72. Nanofiltration system; 73. Reverse osmosis system; 8. Discharge tank. DETAILED DESCRIPTION

[0053] Exemplary embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. Although exemplary embodiments of the present invention are shown in the accompanying drawings, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments set forth herein. Rather, these embodiments are provided to enable a more thorough understanding of the present invention and to fully convey the scope of the present invention to those skilled in the art.

[0054] As shown in FIG1 and FIG2 , an embodiment of the present invention provides a method for treating waste liquid from a uranium purification and conversion nitric acid system, comprising:

[0055] Step 11, pre-treating the uranium purification waste liquid to obtain a first treated liquid;

[0056] Step 12, performing an extraction treatment on the first treatment liquid to recover uranium in the first treatment liquid to obtain a second treatment liquid;

[0057] Step 13, degreasing the second treatment liquid to remove organic matter in the second treatment liquid to obtain a third treatment liquid;

[0058] Step 14, evaporating and concentrating the third treatment liquid to obtain a fourth treatment liquid;

[0059] Step 15: Perform membrane treatment on the fourth treated liquid to obtain a fresh water clear liquid and then discharge it.

[0060] In this embodiment, the uranium purification wastewater contains insoluble solid impurities. At the wastewater receiving end, a flocculant is added to cause these insoluble solid impurities to settle to the bottom of the wastewater receiving tank. When the sediment at the bottom reaches a certain height, filter press is performed to achieve solid-liquid separation.

[0061] Uranium is recovered from the filtrate and supernatant from the wastewater storage tank using TBP (tributyl phosphate) hydrogenated kerosene extraction, combined with dilute nitric acid stripping. The uranium is then recycled back into the production line as stripping liquid. The raffinate from the extraction process is then processed and reused. The lean organic phase from the stripping process is washed and reused.

[0062] Then, the organic phase in the raffinate water is removed by combining an oil removal tower with electrocatalytic oxidation. First, the insoluble organic matter in the raffinate water is removed by the oil removal tower, and then the soluble organic matter in the raffinate water is deeply removed by electrocatalytic oxidation.

[0063] The de-oiled raffinate is treated by evaporation, concentration, and crystallization to remove salt. Crystals are obtained during the evaporation of the raffinate and the mother liquor is separated into solids and then stored in barrels. The mother liquor is returned to the waste liquid receiving terminal, and the condensate generated during the evaporation of the raffinate enters the membrane treatment process.

[0064] The membrane treatment process uses a combined ultrafiltration, nanofiltration, and reverse osmosis process for deep uranium removal. The condensate from the evaporation and concentration system is first treated through an ultrafiltration membrane to remove fine impurities. The freshwater produced during the ultrafiltration process is then passed through a nanofiltration membrane for a first, deep uranium interception. This is followed by a reverse osmosis membrane for a second, deep uranium interception. Ultimately, the freshwater produced during the reverse osmosis process meets the final discharge target of [U] ≤ 50 μg / L.

[0065] In this embodiment, metallic uranium is recovered by flocculation precipitation, extraction, stripping, oil removal, evaporation concentration, and membrane treatment, and impurities in the waste liquid are removed before deep uranium removal, thereby achieving an emission standard of U ≤ 50 μg / L.

[0066] In an optional embodiment of the present invention, the uranium purification waste liquid includes at least one of the following:

[0067] Nitric acid distillation residue;

[0068] Organic phase alkaline washing solution;

[0069] Denitrification tail gas eluent;

[0070] Hydrogen reduction bubbling water.

[0071] In this embodiment, since nitric acid and organic solvents are used in the uranium purification production process, the uranium purification waste liquid will contain substances such as nitric acid and organic solvents, and will also contain nitric acid and an organic phase. Therefore, the uranium purification production process will produce waste liquids such as distillation residue and organic phase alkaline washing liquid, including nitric acid distillation residue, organic phase alkaline washing liquid, denitrification tail gas washing liquid, and hydrogen reduction bubbling water.

[0072] In an optional embodiment of the present invention, step 11 may include:

[0073] A flocculant is added to the uranium purification waste liquid to precipitate insoluble solid impurities in the uranium purification waste liquid and separate them from the uranium purification waste liquid to obtain a first treated liquid.

[0074] In this embodiment, the received waste liquids such as nitric acid distillation residue, organic phase alkaline washing liquid, denitrification tail gas washing liquid, hydrogen reduction bubbling water, etc. are classified and placed;

[0075] The acidity of the nitric acid distillation residue and the organic phase alkaline washing liquid is neutralized to 5 mol / L by adding 30% NaOH, and the waste liquid after neutralization is passed through an oil removal resin tower to separate the waste organic phase entrained in the waste liquid;

[0076] The deoiled waste liquid is then mixed with denitrification tail gas washing liquid and hydrogen reduction tail gas bubbling water to dilute the acidity of the nitric acid distillation residue, and 5% PAM (polyacrylamide) is added at the same time to cause the insoluble impurities in the waste liquid to flocculate and precipitate.

[0077] In an optional embodiment of the present invention, step 12 may include:

[0078] Step 121, extracting the first treatment liquid with a first extractant at a first preset flow ratio, transferring uranium in the first treatment liquid from the aqueous phase to the organic phase, to obtain a loaded organic phase;

[0079] Step 122 , stripping the loaded organic phase with a second extractant at a second flow ratio at a first preset temperature, recovering uranium in the loaded organic phase in the form of a stripping solution to obtain a second treated solution.

[0080] In this embodiment, in step 121, the waste liquid with an acidity of about 2 to 4 mol / L after treatment in step 11 is mixed with the fresh organic phase pre-prepared in the reagent preparation system 34, the lean organic phase returned from the extraction system, and the purified organic phase from the organic phase purification system 33 at a flow ratio of 3:1 between the aqueous phase and the organic phase, and then enters the extraction device 31 for extraction using TBP-hydrogenated kerosene as the extraction agent.

[0081] According to the specific extraction status, the two-phase flow ratio is interlocked and adjusted. After sufficient stirring and mixing and static clarification and separation, the uranium in the aqueous phase is transferred to the organic phase. The uranium content of the outlet loaded organic phase [U] is ≥10g / L, and the uranium content in the raffinate [U] is ≤10mg / L.

[0082] In step 122, the loaded organic phase from step 121 enters the stripping device 32, and 0.01 mol / L HNO3 is used as the extractant, and is in countercurrent contact with the loaded organic phase at a flow ratio of 1:2. The stripping process temperature is controlled to be carried out under an environment of (55±5)°C. After sufficient stirring and mixing and standing for clarification and separation, the uranium in the organic phase is transferred to the aqueous phase, and the stripping solution with [U]>30 g / L is returned to the purification production line, and the lean organic phase is collected and temporarily stored.

[0083] In an optional embodiment of the present invention, step 12 further includes step 123:

[0084] The lean organic phase obtained in step 122 enters the organic phase purification system 33, where impurities are removed by alkaline washing and acid washing.

[0085] Alkali washing uses 5% Na2CO3 solution, and the flow ratio of the lean organic phase to the alkaline washing liquid is controlled at 1:1. The two phases are fully mixed, contacted, and exchanged to achieve cleaning. The mixed liquid after the reaction is allowed to stand to achieve two-phase separation, and the lower aqueous phase is recycled.

[0086] The pickling agent is 2.0 mol / L HNO3, and the flow ratio of the organic phase to the pickling liquid is controlled to be 1:1. The two phases are fully mixed and cleaned, and the mixed liquid is allowed to stand to separate the two phases. The lower aqueous phase is recycled, and the upper organic phase is returned to step 121 for recycling as an extractant.

[0087] In an optional embodiment of the present invention, step 12 may further include step 124:

[0088] The raffinate from step 121 enters an oil-water separation tower to separate the entrained organic phase and aqueous phase. The organic phase returns to the stripping device 32 in step 122, and the aqueous phase enters the oil removal system 5.

[0089] In an optional embodiment of the present invention, step 13 may include:

[0090] Step 131, inputting the second treatment liquid into an oil removal tower to remove insoluble organic matter in the second treatment liquid;

[0091] Step 132 : performing electrocatalytic oxidation treatment on the second treatment liquid to remove soluble organic matter in the second treatment liquid to obtain a third treatment liquid.

[0092] In this embodiment, the aqueous phase from step 124 enters the oil removal system 5. The mixed waste liquid first enters the oil removal tower to remove insoluble organic matter;

[0093] Then it enters the electrocatalytic oxidation device, where the organic matter in the waste liquid is directly degraded through the electrode reaction under the action of an external electric field. The waste liquid with a chemical oxygen demand [COD] less than 100 mg / L after electrocatalytic oxidation is flocculated and settled, and then filtered through a filter press to achieve solid-liquid separation;

[0094] The resulting filter cake is barreled and transported to a uranium-containing non-metallic solid waste pretreatment unit for treatment, and the pH value of the filtrate is adjusted to 6.

[0095] In an optional embodiment of the present invention, step 14 may include:

[0096] Step 141, evaporating and separating the fourth treatment liquid at a second preset temperature to obtain a concentrated liquid;

[0097] Step 142 , evaporating and crystallizing the concentrated liquid to remove salt at a third preset temperature and a preset vacuum degree to obtain salt crystals and the fourth processing liquid.

[0098] In this embodiment, in step 141, the waste liquid treated in step 13 is heat exchanged with the secondary steam condensate generated by the MVR evaporation system in a condensate preheater. The waste liquid is then preheated to 75°C in a non-condensable gas preheater before entering the MVR heater. After being heated to 95°C by steam, the waste liquid enters the MVR evaporation chamber and begins evaporation. The generated steam and entrained tiny droplets rise in the separator, and the entrained droplets are well separated after passing through the baffle.

[0099] The separated secondary steam is compressed by a compressor, raising its temperature and returning to the MVR heater for further recycling. The concentrated liquid is concentrated through forced circulation, raising its concentration to 25%. It is then pumped to the single-effect evaporation system via a transfer pump. A portion of the secondary steam condensate enters step 122 for preparation of the stripping agent.

[0100] In step 142, the waste liquid treated in step 141 enters the single-effect evaporation system. The waste liquid enters the single-effect heater and is heated by raw steam to 70° C. before being sent to the single-effect evaporation chamber for separation. While feeding, the system is evacuated to a vacuum degree of about -0.09 MPa.

[0101] The concentrated saturated liquid produced during the single-effect evaporation process is transported to the thickening kettle, where it is cooled by circulating cooling water to cause crystals to precipitate, and the slurry is separated into solid and liquid by a centrifuge;

[0102] The solid after centrifugation is barreled and sent for drying, and the centrifuged waste liquid is returned to step 12 for uranium recovery.

[0103] In an optional embodiment of the present invention, step 15 may include:

[0104] Step 151 : filtering the fourth treatment liquid through an ultrafiltration membrane to remove uranium molecules in the fourth treatment liquid to obtain a first filtrate.

[0105] In this embodiment, the condensed water produced after step 142 is mixed with the hydrogen reduction tail gas eluent and the denitrification tail gas eluent and then enters the ultrafiltration system 71 to remove large molecular impurities. The ultrafiltration concentrate is returned to the electrocatalytic oxidation device in step 13, and the ultrafiltered fresh water enters the nanofiltration system 72.

[0106] In an optional embodiment of the present invention, step 15 further includes:

[0107] Step 152: Filter the first filtrate through a nanofiltration membrane to remove impurities with a diameter greater than a preset length in the first filtrate to obtain a second filtrate.

[0108] In this embodiment, the ultrafiltered freshwater after step 151 enters nanofiltration system 72, where impurities such as floating objects and uranium particles with diameters greater than 5 μm are trapped in the wastewater. The concentrated water produced by nanofiltration returns to the electrocatalytic oxidation device in step 13, and the nanofiltered freshwater enters reverse osmosis system 73.

[0109] In an optional embodiment of the present invention, step 15 further includes:

[0110] Step 153 : Passing the second filtrate through a reverse osmosis membrane to remove salt particles in the second filtrate, obtaining a fresh water clear liquid with a uranium content of ≤50 μg / L, and discharging the fresh water clear liquid.

[0111] In this embodiment, the nanofiltered freshwater after step 152 enters the reverse osmosis system 73 to intercept impurities such as salt in the wastewater. The concentrated water produced by the reverse osmosis of the wastewater returns to the electrocatalytic oxidation device in step 13, and the freshwater after reverse osmosis enters the discharge tank 8.

[0112] In an optional embodiment of the present invention, the method for treating uranium purification waste liquid further includes step 16:

[0113] The fresh water in the discharge tank 8 is sampled and analyzed. When the uranium content [U] is ≤ 50 μg / L, it can be discharged; when the uranium content [U] is greater than 50 μg / L, return to step 15 and process again.

[0114] As shown in FIG3 , an embodiment of the present invention further provides a waste liquid treatment system for a uranium purification and conversion into nitric acid system, comprising:

[0115] The waste liquid receiving device 1, the oil removal resin tower 2, the extraction device 31, the stripping device 32, the oil-water separation tower 4, the oil removal system 5, the evaporation system, the membrane treatment system and the discharge tank 8 are connected in sequence;

[0116] an organic phase purification system 33 in communication with the stripping device 32;

[0117] a reagent preparation system 34 in communication with the extraction device 31;

[0118] The oil removal system 5 includes an electrocatalytic oxidation device and a filter press connected to the electrocatalytic oxidation device;

[0119] The evaporation system includes a multi-effect evaporation system 61 and a single-effect evaporation system 62 connected to the multi-effect evaporation system 61;

[0120] The membrane treatment system includes an ultrafiltration system 71, a nanofiltration system 72 and a reverse osmosis system 73 which are connected in sequence;

[0121] The waste liquid receiving device 1 pre-treats the uranium purification waste liquid to obtain a first treated liquid;

[0122] The first treatment liquid is input into the extraction device 31 and the stripping device 32, and the first treatment liquid is subjected to extraction treatment to recover uranium in the first treatment liquid to obtain a second treatment liquid;

[0123] The second treatment liquid is input into the oil removal system 5, and the oil is removed from the second treatment liquid to remove organic matter in the second treatment liquid to obtain a third treatment liquid;

[0124] The third treatment liquid is input into the evaporation system, and the third treatment liquid is evaporated and concentrated to obtain a fourth treatment liquid;

[0125] The fourth treated liquid is input into the membrane treatment system, and the fourth treated liquid is subjected to membrane filtration treatment to obtain a fresh water clear liquid, which is then discharged into the discharge tank 8.

[0126] In this embodiment, uranium purification wastewater is received by wastewater receiving device 1 according to wastewater type. Each wastewater receiving device is equipped with real-time detection instruments. When the liquid level reaches the upper limit, an alarm is triggered and the inlet valve is closed. When the liquid level drops to the lower limit, the outflow pump is stopped.

[0127] The nitric acid distillation residue and the organic phase alkaline washing liquid in the waste liquid receiving device 1 are first neutralized to 5 mol / L by adding 30% NaOH, and the waste organic phase entrained in the waste liquid is separated by the deoiling resin tower 2. The deoiled waste liquid is then mixed with the denitrification tail gas washing liquid and the hydrogen reduction tail gas bubbling water to dilute the acidity of the nitric acid distillation residue. At the same time, 5% PAM (polyacrylamide) is added to cause the insoluble impurities in the waste liquid to flocculate and precipitate, thereby realizing solid-liquid separation.

[0128] The waste liquid after solid-liquid separation is fed into the extraction device 31, where TBP hydrogenated kerosene is used as an extractant to extract the waste liquid, so that the uranium in the aqueous phase is transferred to the organic phase, and the loaded organic phase [U] is ≥ 10 g / L, and the raffinate [U] is ≤ 10 mg / L.

[0129] The loaded organic phase is input into the stripping device 32, and dilute nitric acid is used as the extractant to strip the loaded organic phase. The uranium in the organic phase is transferred to the aqueous phase. The stripping solution with [U]>30g / L is returned to the purification production line, and the lean organic phase is collected and temporarily stored to achieve uranium recovery.

[0130] The lean organic phase is input into the organic phase purification system 33, where impurities are removed by alkali washing and acid washing. The two phases are fully mixed and washed, and the mixed liquid is allowed to stand to separate the two phases. The lower aqueous phase is recycled, and the upper organic phase is recycled as an extractant.

[0131] The raffinate from the extraction unit 31 enters the oil-water separation tower 4, where the entrained organic phase is separated from the aqueous phase. The organic phase returns to the stripping unit 32, while the aqueous phase enters the oil removal system 5. This aqueous mixture first enters the oil removal tower to remove insoluble organic matter, then enters the electrocatalytic oxidation unit, where an electrode reaction under the action of an external electric field directly degrades the organic matter in the wastewater. It is then filtered through a filter press to achieve solid-liquid separation. The resulting filter cake is barreled and transported to the uranium-containing non-metallic solid waste pretreatment unit for treatment.

[0132] The waste liquid outputted from the oil removal system 5 enters the evaporation system, and is evaporated, concentrated, and crystallized by the multi-effect evaporation system 61 and the single-effect evaporation system 62 .

[0133] Specifically, the waste liquid first enters the multi-effect evaporation system 61, and undergoes heat exchange with the secondary steam condensate generated by the MVR evaporation system in the condensate preheater. It is then preheated to 75°C in the non-condensable gas preheater and then enters the MVR heater. After being heated to 95°C by steam, it enters the MVR evaporation chamber and begins to evaporate. The generated steam and entrained tiny droplets rise in the separator, and the entrained droplets are well separated after passing through the baffle. The separated secondary steam is compressed by the compressor and its temperature is increased, and it continues to return to the MVR heater for recycling. The concentrated liquid is concentrated through forced circulation, and after the concentration is increased to 25%, it is pumped to the single-effect evaporation system 62 through the transfer pump. A portion of the secondary steam condensate enters the stripping device 32 for the preparation of the stripping agent;

[0134] After the concentrate enters the single-effect evaporation system 62, it is heated to 70°C with live steam and then fed into the single-effect evaporation chamber for separation. Simultaneously with the feed, the system is evacuated to a vacuum level of approximately -0.09 MPa. The concentrated saturated liquid produced during the single-effect evaporation process is transferred to a thickening kettle, where it is cooled by circulating cooling water to precipitate crystals. The slurry is then centrifuged for solid-liquid separation. The solids after centrifugation are barreled and dried, and the waste liquid is returned to the extraction unit 31 and stripping unit 32 for uranium recovery.

[0135] The condensed water treated by the single-effect evaporation system 62 and the hydrogen reduction tail gas eluent and the denitrification tail gas eluent are mixed and input into the membrane treatment system. The ultrafiltration system 71, the nanofiltration system 72 and the reverse osmosis system 73 are used to intercept the large molecular particle impurities, floating objects with a diameter greater than 5um, particles and other impurities, as well as salt and other impurities in the mixed liquid, and the obtained fresh water clear liquid is discharged into the discharge tank 8 for sampling and analysis.

[0136] The waste liquid treatment system for the purification and conversion of nitric acid system of this embodiment adopts a process route combining multiple waste liquid treatment methods, giving full play to the advantages of each waste liquid treatment method and realizing the organic combination of multiple waste liquid treatment methods.

[0137] The uranium purification and conversion to nitric acid system waste liquid treatment method and system described in the above embodiments of the present invention adopt a process route that combines multiple waste liquid treatment methods, fully leveraging the advantages of each waste liquid treatment method and achieving an organic combination of multiple waste liquid treatment methods. The uranium-containing deep purification process uses electrocatalytic oxidation to remove organic matter from the waste liquid. During the catalytic oxidation of the organic matter, electron transfer occurs only between the electrode and the wastewater components. The oxidation reaction is carried out by hydroxyl radicals generated by the system itself, requiring no additional liquid or catalyst, and resulting in no secondary pollution. The process can directly recover uranium from the uranium purification waste liquid in the form of a stripping solution, avoiding the problem of uranium-containing solid precipitates generated during the precipitation recovery process being difficult to reuse due to their high impurity content. The process can effectively reduce the uranium content in the uranium-containing waste liquid, achieving an emission standard of [U] ≤ 50 μg / L for the final discharged waste liquid. Compared with traditional ion exchange and precipitation methods, the process is clean, environmentally friendly, and energy-saving, with a high degree of automation and significant economic benefits.

[0138] The above is a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A method for treating waste liquid from a uranium purification and conversion nitric acid system, characterized in that: include: pre-treating the uranium purification waste liquid to obtain a first treated liquid; performing an extraction treatment on the first treatment liquid to recover uranium in the first treatment liquid to obtain a second treatment liquid; Degreasing the second treatment liquid to remove organic matter in the second treatment liquid to obtain a third treatment liquid; Evaporating and concentrating the third treatment liquid to obtain a fourth treatment liquid; The fourth treated liquid is subjected to membrane treatment to obtain a fresh water clear liquid and then discharged.

2. The method for treating waste liquid from a uranium purification and conversion nitric acid system according to claim 1, wherein: The uranium purification waste liquid includes at least one of the following: Nitric acid distillation residue; Organic phase alkaline washing solution; Denitrification tail gas eluent; Hydrogen reduction bubbling water.

3. The method for treating waste liquid from a uranium purification and conversion nitric acid system according to claim 1, wherein: The pre-treating of the uranium purification waste liquid to obtain a first treated liquid comprises: A flocculant is added to the uranium purification waste liquid to precipitate insoluble solid impurities in the uranium purification waste liquid and separate them from the uranium purification waste liquid to obtain a first treated liquid.

4. The method for treating waste liquid from a uranium purification and conversion nitric acid system according to claim 1, wherein: The first treatment liquid is subjected to extraction treatment to recover uranium in the first treatment liquid to obtain a second treatment liquid, comprising: extracting the first treatment liquid with a first extractant at a first preset flow ratio, transferring uranium in the first treatment liquid from the uranium in the aqueous phase to the organic phase, thereby obtaining a loaded organic phase; At a first preset temperature, the loaded organic phase is stripped with a second extractant at a second flow ratio, and uranium in the loaded organic phase is recovered in the form of a stripping solution to obtain a second treated solution.

5. The method for treating waste liquid from a uranium purification and conversion nitric acid system according to claim 1, wherein: Degreasing the second treatment liquid to remove organic matter in the second treatment liquid to obtain a third treatment liquid, comprising: Inputting the second treatment liquid into an oil removal tower to remove insoluble organic matter in the second treatment liquid; The second treatment liquid is subjected to electrocatalytic oxidation treatment to remove soluble organic matter in the second treatment liquid to obtain a third treatment liquid.

6. The method for treating waste liquid from a uranium purification and conversion nitric acid system according to claim 1, characterized in that: The third treatment liquid is evaporated and concentrated to obtain the fourth treatment liquid, comprising: At a second preset temperature, evaporating and separating the fourth treatment liquid to obtain a concentrated liquid; At a third preset temperature and a preset vacuum degree, the concentrated liquid is evaporated and crystallized to remove salt, thereby obtaining salt crystals and the fourth treatment liquid.

7. The method for treating waste liquid from a uranium purification and conversion nitric acid system according to claim 1, characterized in that: The fourth treated liquid is subjected to membrane treatment to obtain a fresh water clear liquid and then discharged, comprising: The fourth treatment liquid is filtered through an ultrafiltration membrane to remove uranium molecules in the fourth treatment liquid to obtain a first filtrate.

8. The method for treating waste liquid from a uranium purification and conversion into nitric acid system according to claim 7, characterized in that: Also includes: The first filtrate is filtered through a nanofiltration membrane to remove impurities with a diameter greater than a preset length in the first filtrate to obtain a second filtrate.

9. The method for treating waste liquid from a uranium purification and conversion into nitric acid system according to claim 8, characterized in that: Also includes: The second filtrate is passed through a reverse osmosis membrane to remove salt particles in the second filtrate, thereby obtaining a fresh water clear liquid with a uranium content of ≤50 μg / L, and discharging the fresh water clear liquid.

10. A waste liquid treatment system for uranium purification and conversion into nitric acid, characterized in that: include: A waste liquid receiving device (1), an oil-removing resin tower (2), an extraction device (31), a stripping device (32), an oil-water separation tower (4), an oil removal system (5), an evaporation system, a membrane treatment system and a discharge tank (8) are sequentially connected; an organic phase purification system (33) in communication with the stripping device (32); a reagent preparation system (34) in communication with the extraction device (31); The oil removal system (5) includes an electrocatalytic oxidation device and a filter press connected to the electrocatalytic oxidation device; The evaporation system includes a multi-effect evaporation system (61) and a single-effect evaporation system (62) connected to the multi-effect evaporation system (61); The membrane treatment system includes an ultrafiltration system (71), a nanofiltration system (72) and a reverse osmosis system (73) which are connected in sequence; The waste liquid receiving device (1) pre-treats the uranium purification waste liquid to obtain a first treated liquid; The first treatment liquid is input into an extraction device (31) and a stripping device (32), and the first treatment liquid is subjected to extraction treatment to recover uranium in the first treatment liquid to obtain a second treatment liquid; The second treatment liquid is input into the oil removal system (5), and the oil is removed from the second treatment liquid to remove organic matter in the second treatment liquid to obtain a third treatment liquid; The third treatment liquid is input into the evaporation system, and the third treatment liquid is evaporated and concentrated to obtain a fourth treatment liquid; The fourth treated liquid is input into the membrane treatment system, and the fourth treated liquid is subjected to membrane filtration treatment to obtain a fresh water clear liquid, which is then discharged into the discharge tank (8).

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