Method for preparing a crystallization agent based on an ammonium diuranate precipitate mother liquor

Abstract

The application relates to a preparation method of a crystallizing agent based on an ammonium diuranate precipitation mother liquor, which is applied to a crystallizing agent preparation system based on an ammonium diuranate precipitation mother liquor. The method is used for recycling an ammonium diuranate precipitation mother liquor in a uranium purification process route to prepare an ammonium carbonate solution. The crystallizing agent preparation system based on the ammonium diuranate precipitation mother liquor comprises a solid-liquid separation component, a deamination component, a carbonization synthesis component and a storage tank component. The deamination component comprises a stripping tower, a water vapor generating device, a condenser, a three-way valve A, a three-way valve B and a three-way valve C. The carbonization synthesis component comprises a filler tower A, a Venturi mixer, a carbon dioxide vaporizer, a liquid carbon dioxide storage tank and a three-way valve D. The ammonium diuranate precipitation mother liquor in the uranium purification process route is recycled to prepare the ammonium carbonate solution. The ammonium carbonate solution can be returned to the uranium purification process route to be used as a crystallizing agent, so that the production cost of uranium purification is reduced.

Description

Technical Field

[0001] This invention relates to the field of natural uranium purification technology in the nuclear industry, and in particular to a method for preparing a crystallizing agent based on ammonium diuranate precipitate mother liquor. Background Technology

[0002] Natural uranium purification (from yellowcake to nuclear-grade UO2) is the front end of nuclear fuel production and plays an important role in the nuclear energy industry. The uranium purification process includes the following steps: 1. Yellowcake reacts with nitric acid to prepare uranyl nitrate (UNH) with high impurities; 2. Uranyl nitrate (UNH) is extracted with TBP-sulfonated kerosene and back-extracted with micro-nitric acid to obtain nuclear-grade uranyl nitrate (UNH); 3. Uranyl nitrate (UNH) reacts with ammonium hydroxide (NH4OH) to prepare ammonium diuranate (ADU); 4. Ammonium diuranate (ADU) reacts with ammonium carbonate ((NH4)2CO3) to prepare ammonium tricarbonate (AUC); 5. Ammonium tricarbonate (AUC) is filtered and calcined to obtain nuclear-grade UO2.

[0003] In the above process route, the process of preparing ammonium diuranate by precipitating uranyl nitrate with ammonia (corresponding to the third sub-step above) has been used since the late 1950s, and its chemical reaction formula is as follows: The precipitate produced by the reaction contains... , , , Plasma is easily recyclable, reducing resource waste.

[0004] Currently, the main methods for recovering the above-mentioned precipitate mother liquor are used to recover nitrate and ammonium ions. The specific steps are as follows:

[0005] 1. First, concentrated sulfuric acid is added to the mother liquor to convert nitrate ions into nitric acid. Then, the solution after the reaction is heated to convert the nitric acid into nitric acid vapor. Finally, the condensed nitric acid is collected to obtain nitric acid with a concentration of 40%, thus achieving the recovery of nitrate ions. The chemical reaction formula is as follows: ;

[0006] 2. Add lime milk to the ammonium bisulfate solution obtained in the previous step to convert the fixed ammonium into free ammonium. Then, heat the solution to convert the free ammonium into gaseous ammonia. Finally, collect the condensed gaseous ammonia to obtain ammonia water with a concentration of less than 25%, thus achieving the recovery of ammonium ions. The chemical reaction formula is as follows: .

[0007] The above-mentioned method for recovering the mother liquor from the precipitate has the following shortcomings in practical applications: Adding concentrated sulfuric acid introduces sulfate ions, changing the nitrate system solution into a sulfate system solution. Then, adding lime milk causes sulfate ions to combine with calcium ions to form calcium sulfate precipitate. This is equivalent to generating a new byproduct (calcium sulfate precipitate) while recovering nitrate and ammonium ions. Furthermore, since the mother liquor itself contains radioactive uranium, the calcium sulfate precipitate produced will inevitably also contain radioactive uranium. Calcium sulfate precipitate containing radioactive uranium cannot be commercially sold and is difficult to further deuraniumize. Summary of the Invention

[0008] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method for preparing a crystallizer based on ammonium diuranate precipitate mother liquor. This method solves the problem that current methods for recovering ammonium diuranate precipitate mother liquor produce difficult-to-handle byproducts.

[0009] The technical solution of the present invention is: a method for preparing a crystallizer based on ammonium diuranate precipitate mother liquor, which is applied to a crystallizer preparation system based on ammonium diuranate precipitate mother liquor. The method is for recovering ammonium diuranate precipitate mother liquor in the uranium purification process to prepare an ammonium carbonate solution.

[0010] The crystallizer preparation system based on ammonium diuranate precipitation mother liquor includes a solid-liquid separation component, a deammoniation component, a carbonization synthesis component, and a storage tank component.

[0011] The solid-liquid separation assembly includes a thickener, a plate and frame filter press, and a static pressure filter. The filtrate overflowing from the thickener is connected to the plate and frame filter press, and the filtrate discharged from the plate and frame filter press is connected to the static pressure filter.

[0012] The ammonia removal assembly includes a stripping tower, a steam generator, a condenser, three-way valves A, B, and C, and a shell-and-tube heat exchanger A. The stripping tower contains, from bottom to top, a bottom liquid chamber, a gas-liquid mass transfer chamber, and an ammonia chamber. The top of the stripping tower has an ammonia outlet connected to the ammonia chamber, and the bottom of the stripping tower has a bottom liquid outlet connected to the bottom liquid chamber. A steam inlet connected to the interface between the bottom liquid chamber and the gas-liquid mass transfer chamber is located on the side wall of the stripping tower, as is a bottom liquid return valve connected to the interface between the bottom liquid chamber and the gas-liquid mass transfer chamber. The stripping tower has an ammonia reflux port on its side wall, connecting to the junction of the gas-liquid mass transfer chamber and the ammonia chamber. It also has a mother liquor alkali inlet on its side wall, connecting to the gas-liquid mass transfer chamber. A steam generator is connected to the steam inlet of the stripping tower. The condenser has a gas phase inlet, a liquid phase outlet, and a non-condensable gas outlet; the gas phase inlet of the condenser is connected to the ammonia outlet of the stripping tower. Three-way valve A has a first port, a second port, and a third port; the first port of three-way valve A is connected to the liquid phase outlet of the condenser, and the second port of three-way valve A is connected to the steam outlet of the stripping tower. The ammonia reflux port of the stripping tower is connected, and the third port of three-way valve A is used to output ammonia water; three-way valve B has a fourth, fifth, and sixth port. The fourth port of three-way valve B is connected to the mother liquor / alkali inlet of the stripping tower, the fifth port of three-way valve B is used to receive alkali, and the sixth port of three-way valve B is used to receive mother liquor; three-way valve C has a seventh, eighth, and ninth port. The seventh port of three-way valve C is connected to the bottom liquid outlet of the stripping tower, and the eighth port of three-way valve C is connected to the bottom liquid reflux port of the stripping tower. The ninth port of valve C is used to discharge the bottom liquid of the tower; the shell-and-tube heat exchanger A is located between the mother liquor storage tank and the three-way valve C. The shell-and-tube heat exchanger A is provided with a shell-side inlet, a shell-side outlet, a tube-side inlet, and a tube-side outlet; the shell-side inlet of the shell-and-tube heat exchanger A is connected to the outlet A of the mother liquor storage tank, the shell-and-tube outlet of the shell-and-tube heat exchanger A is connected to the sixth port of the three-way valve B, the tube-side inlet of the shell-and-tube heat exchanger A is connected to the ninth port of the three-way valve C, and a pipe for discharging the bottom liquid of the tower is connected to the tube-side outlet of the shell-and-tube heat exchanger A.

[0013] The carbonization synthesis assembly includes a packed tower A, a Venturi mixer, a carbon dioxide vaporizer, a liquid carbon dioxide storage tank, and a three-way valve D. The packed tower A has, from bottom to top, a bottom liquid chamber, a carbonization synthesis chamber, and a tail gas chamber. A water spray component is located at the interface between the carbonization synthesis chamber and the tail gas chamber inside the packed tower A, used to spray water mist into the carbonization synthesis chamber. A deionized water inlet is located on the side wall of the packed tower A, connecting to the water spray component. A tail gas outlet is located at the top of the packed tower A, connecting to the tail gas chamber. A bottom liquid outlet is located at the bottom of the packed tower A, connecting to the bottom liquid chamber. A gas-liquid mixing inlet is located on the side wall of the packed tower A, connecting to the interface between the bottom liquid chamber and the carbonization synthesis chamber. The packed tower A has an ammonia water inlet on its side wall, which connects to the carbonization synthesis chamber. The venturi mixer has a solution inlet and a gas inlet at its upper end, and a gas-liquid mixing outlet at its lower end, which connects to the gas-liquid mixing inlet of the packed tower A. The carbon dioxide vaporizer has a liquid inlet and a gas outlet at both ends, with the liquid inlet connected to a liquid carbon dioxide storage tank and the gas outlet connected to the gas inlet of the venturi mixer. The three-way valve D has a tenth port, an eleventh port, and a twelfth port. The tenth port of the three-way valve D connects to the bottom liquid outlet of the packed tower A, and the eleventh port of the three-way valve D connects to the solution inlet of the venturi mixer.

[0014] The storage tank assembly includes a mother liquor storage tank, an alkali storage tank, an ammonia storage tank, and an ammonium carbonate solution storage tank. The mother liquor storage tank has an inlet A and an outlet A. The inlet A of the mother liquor storage tank is connected to a static pressure filter, and the outlet A of the mother liquor storage tank is connected to the sixth port of a three-way valve B. The alkali storage tank is connected to the fifth port of the three-way valve B. The ammonia storage tank has an inlet C and an outlet C. The inlet C of the ammonia storage tank is connected to the third port of the three-way valve A, and the outlet C of the ammonia storage tank is connected to the ammonia inlet of the packed tower A. The ammonium carbonate solution storage tank is connected to the twelfth port of a three-way valve D.

[0015] The steps are as follows:

[0016] S01, Removal of solid phase:

[0017] a. The thickener performs preliminary solid-liquid separation on the product of the reaction between uranyl nitrate and ammonium hydroxide. The solid phase ammonium diuranate is discharged and enters the subsequent process of uranium purification to prepare ammonium tricarbonate. The liquid phase precipitate mother liquor flows into the plate and frame filter press through the pipeline, waiting for further solid-liquid separation.

[0018] b. The plate and frame filter press retains the fine crystals remaining in the mother liquor. The liquid phase obtained after retention flows into the static pressure filter for further solid-liquid separation.

[0019] c. The static pressure filter is used to check and filter the mother liquor, further filtering out the fine crystals remaining in the mother liquor, so that the uranium content in the mother liquor discharged from the static pressure filter is <15mg / L, and the suspended solids (SS) is <200mg / L.

[0020] d. The mother liquor discharged from the static pressure filter enters the mother liquor storage tank and is left to stand for 3 to 5 months to reduce its radioactivity to the level of natural uranium.

[0021] SO2, fixed ammonia is converted into free ammonium:

[0022] a. After standing and storing, the precipitated mother liquor is fed into the shell cavity of shell-and-tube heat exchanger A. The precipitated mother liquor in the shell cavity exchanges heat with the bottom liquid in the tube cavity of shell-and-tube heat exchanger A, and the temperature rises. Then, it enters the gas-liquid mass transfer chamber of the stripping tower through the sixth port of the three-way valve B, the fourth port of the three-way valve B, and the mother liquor alkali inlet of the stripping tower, and is sprayed downward.

[0023] b. The sodium hydroxide solution stored in the alkali storage tank enters the gas-liquid mass transfer chamber of the stripping tower through the fifth port of the three-way valve B, the fourth port of the three-way valve B, and the mother liquor alkali inlet of the stripping tower, and is sprayed downwards.

[0024] c. The high-temperature steam produced by the steam generator enters the gas-liquid mass transfer chamber of the stripper through the steam inlet and flows upward.

[0025] d. In the gas-liquid mass transfer chamber of the stripping tower, upward-flowing water vapor comes into countercurrent contact with the downward-sprayed mixed liquid, undergoing gas-liquid mass transfer and the following chemical reactions occur: The sodium nitrate and ammonium hydroxide solutions produced in the reaction flow downwards and collect in the bottom liquid chamber of the stripping tower, forming the bottom liquid. In the bottom liquid chamber of the stripping tower, ammonium hydroxide decomposes endothermally, undergoing the following decomposition reaction: The water produced by decomposition remains in the liquid chamber of the tower bottom, while the ammonia produced by decomposition flows upward and is discharged to the outside of the stripping tower through the gas-liquid mass transfer chamber, the ammonia chamber, and the ammonia outlet in sequence. Based on the above two reactions, the fixed ammonia in the precipitated mother liquor is converted into free ammonia.

[0026] Steps a, b, and c of this process are performed simultaneously; in step d of this process, the mixed solution is obtained by mixing sodium hydroxide solution with the mother liquor of the precipitate.

[0027] S03, treatment of bottom liquid in the tower:

[0028] The liquid in the bottom chamber of the stripping tower was sampled and the ammonia nitrogen content was tested.

[0029] If [NH4±N] < 15 mg / L, then connect the seventh and ninth ports of the three-way valve C. The bottom liquid in the stripping tower is discharged from the bottom liquid outlet of the stripping tower and then enters the tube cavity of the shell-and-tube heat exchanger through the three-way valve C. The bottom liquid in the tube cavity of the shell-and-tube heat exchanger exchanges heat with the precipitated mother liquor in the shell cavity of the shell-and-tube heat exchanger to preheat the precipitated mother liquor. The bottom liquid after heat exchange is discharged from the tube cavity of the shell-and-tube heat exchanger A as wastewater or enters the wastewater treatment process to recover nitrate.

[0030] If [NH4±N]≥15mg / L, then connect the seventh and eighth ports of the three-way valve C. The liquid in the bottom chamber of the stripping tower will be discharged from the bottom liquid outlet of the stripping tower and then returned to the bottom liquid chamber of the stripping tower through the three-way valve C and the bottom liquid reflux port of the stripping tower to continue the decomposition reaction of ammonium hydroxide.

[0031] S04, collecting ammonia water:

[0032] a. The gas in the ammonia chamber of the stripping tower is a mixture of ammonia, water vapor, and other non-condensable gases. After the mixed gas is discharged from the ammonia outlet of the stripping tower, it enters the condenser through the gas phase inlet and condenses to form ammonia water. The reactions that occur during the condensation process are as follows: Ammonia water is discharged through the liquid phase outlet of the condenser, and non-condensable gas is discharged from the non-condensable gas outlet of the condenser. It then enters the waste gas treatment process to convert the free ammonium in it into fixed ammonia.

[0033] b. Sample the ammonia water discharged from the liquid phase outlet of the condenser and test the ammonia water concentration;

[0034] If the mass fraction of ammonia water is between 15-20%, then connect the first port and the third port of the three-way valve A, and the ammonia water discharged from the liquid phase outlet of the condenser will enter the ammonia water storage tank through the three-way valve A for storage.

[0035] If the mass fraction of ammonia is less than 15%, then the first port of the three-way valve A is connected to the second port. The ammonia discharged from the liquid phase outlet of the condenser returns to the gas-liquid mass transfer chamber of the stripping tower through the three-way valve A and the ammonia return port of the stripping tower, where it undergoes the following decomposition reaction: At the same time, the supply of high-temperature steam to the stripping tower is reduced, thereby increasing the ammonia concentration in the ammonia chamber of the stripping tower.

[0036] If the mass fraction of ammonia water is higher than 20%, then the first port and the second port of the three-way valve A are connected. The ammonia water discharged from the liquid phase outlet of the condenser returns to the gas-liquid mass transfer chamber of the stripping tower through the three-way valve A and the ammonia water return port of the stripping tower, and undergoes the following decomposition reaction: At the same time, the supply of high-temperature steam to the stripping tower is increased, thereby reducing the ammonia concentration in the ammonia chamber of the stripping tower.

[0037] S05, ammonia carbonization treatment:

[0038] a. The ammonia water stored in the ammonia water storage tank is discharged and enters the carbonization synthesis chamber of packed tower A through the ammonia water inlet of packed tower A;

[0039] b. After being vaporized by the carbon dioxide vaporizer, the liquid carbon dioxide stored in the liquid carbon dioxide storage tank enters the carbonization synthesis chamber of the packed tower A through the gas inlet of the Venturi mixer, the gas-liquid mixing outlet of the Venturi mixer, and the gas-liquid mixing inlet of the packed tower A in sequence.

[0040] c. Ammonia and carbon dioxide come into full contact in the carbonization and synthesis chamber of packed tower A, and the following chemical reaction occurs: The ammonium carbonate solution produced by the reaction flows downwards and collects in the bottom liquid chamber of packed tower A.

[0041] d. The water spraying component sprays water mist into the carbonization synthesis chamber, thereby forming a water seal between the carbonization synthesis chamber and the tail gas chamber of the packed tower A. This seal is used to dissolve the ammonia gas volatilized from the ammonia water and prevent the ammonia gas from entering the tail gas chamber and being discharged through the tail gas chamber.

[0042] e. Sample and test the ammonium carbonate solution discharged from the bottom liquid outlet of packed tower A. The following two scenarios are handled: Ⅰ. If the ammonium carbonate concentration is below 350 g / L, it is considered an unqualified ammonium carbonate solution. Connect the tenth and eleventh ports of the three-way valve D, allowing the ammonium carbonate solution discharged from the bottom liquid outlet of packed tower A to sequentially pass through the three-way valve D, the Venturi mixer, and the gas-liquid mixing inlet of packed tower A back into the carbonation synthesis chamber of packed tower A for concentration. Ⅱ. If the ammonium carbonate concentration reaches 350 g / L, it is considered a qualified ammonium carbonate solution. Connect the tenth and twelfth ports of the three-way valve D, allowing the ammonium carbonate solution discharged from the bottom liquid outlet of packed tower A to be input into the ammonium carbonate solution storage tank through the three-way valve D for later use.

[0043] Steps a and b of this step are performed simultaneously, as are steps c and d of this step.

[0044] A further technical solution of the present invention is as follows: the crystallizer preparation system based on ammonium diuranate precipitate mother liquor further includes a tail gas treatment component; the tail gas treatment component includes a packed tower B and a dilute nitric acid storage tank; the packed tower B has a liquid phase chamber, a packed absorption chamber, and a gas phase chamber arranged sequentially from bottom to top inside; a spray component is provided at the junction of the packed absorption chamber and the gas phase chamber inside the packed tower B, the spray component is used to spray mist-like dilute nitric acid into the packed absorption chamber; the top of the packed tower B has a non-condensable gas outlet connected to the gas phase chamber; the side wall of the packed tower B has a dilute nitric acid inlet connected to the spray component; the side wall of the packed tower B has a non-condensable gas inlet connected to the junction of the liquid phase chamber and the packed absorption chamber; the side wall of the packed tower B has a tail gas inlet connected to the junction of the liquid phase chamber and the packed absorption chamber; the bottom of the packed tower B has an ammonium nitrate solution outlet connected to the liquid phase chamber; the non-condensable gas inlet of the packed tower B is connected to the non-condensable gas outlet of the condenser; the tail gas inlet of the packed tower B is connected to the tail gas outlet of the packed tower A; the dilute nitric acid storage tank is connected to the dilute nitric acid inlet of the packed tower B;

[0045] The method also includes step S06, which follows step S05.

[0046] S06, Exhaust gas treatment:

[0047] a. The non-condensable gas discharged from the ammonia outlet of the stripping tower passes sequentially through the gas phase inlet of the condenser, the non-condensable gas outlet of the condenser, and the non-condensable gas inlet of the packed tower B, and enters the packing absorption chamber of the packed tower B, flowing upward.

[0048] b. The exhaust gas discharged from the tail gas outlet of packed tower A enters the packing absorption chamber of packed tower B through the tail gas inlet of packed tower B and flows upward.

[0049] c. The dilute nitric acid in the dilute nitric acid storage tank enters the spray component of the packed tower B through the dilute nitric acid inlet and is sprayed downwards.

[0050] d. The upward-flowing ammonia gas comes into countercurrent contact with the downward-spraying dilute nitric acid, resulting in gas-liquid mass transfer and the following chemical reaction: The ammonium nitrate solution produced by the reaction flows downwards and collects in the liquid phase cavity;

[0051] Steps a, b, and c in this process are performed simultaneously. After this step is completed, the ammonium nitrate solution collected in the liquid phase chamber of packed tower B is sent back to the deammoniation assembly for recycling.

[0052] A further technical solution of the present invention is as follows: in sub-steps b and c of step S01, the fine crystals contain ammonium diuranate and uranium oxide impurities; the filter residue filtered by the plate and frame filter press and the static pressure filter are returned to the thickener to avoid uranium loss.

[0053] A further technical solution of the present invention is as follows: In sub-step c of step S01, if the precipitated mother liquor discharged from the static pressure filter does not meet the requirements of uranium content <15mg / L and suspended solids SS <200mg / L, then check whether the filtration functions of the thickener, plate and frame filter press and static pressure filter are normal. After the filtration functions of the thickener, plate and frame filter press and static pressure filter are adjusted to normal, the precipitated mother liquor is returned to the thickener to remove the solid phase again.

[0054] A further technical solution of the present invention is as follows: In sub-step d of step S02, the temperature of the ammonia chamber of the stripping tower is controlled between 90-100℃. The temperature control of the ammonia chamber can be achieved by adjusting the amount of high-temperature steam entering the stripping tower. The temperature of the bottom liquid in the bottom liquid chamber of the stripping tower is controlled between 95-105℃. The temperature control of the bottom liquid can be achieved by adjusting the amount of high-temperature steam entering the stripping tower. The pH of the bottom liquid in the bottom liquid chamber of the stripping tower is controlled between 10-13. The pH control of the bottom liquid can be achieved by adjusting the amount of sodium hydroxide solution entering the tower.

[0055] A further technical solution of the present invention is as follows: in sub-step b of SO2 step, the mass fraction of sodium hydroxide solution is 20-50%; in sub-step c of SO2 step, the temperature of high-temperature steam is between 95-100℃.

[0056] A further technical solution of the present invention is as follows: a separation chamber is provided inside the thickener, and an overflow port for discharging the clarified liquid from the upper part of the separation chamber is provided on the upper side wall of the thickener; a plate and frame filter press is provided with an inlet D and an outlet D, the inlet D of the plate and frame filter press is connected to the overflow port of the thickener to receive the clarified liquid discharged from the thickener; a static pressure filter is provided with an inlet E and an outlet E, the inlet E of the static pressure filter is connected to the outlet E of the plate and frame filter press to receive the filtrate discharged from the plate and frame filter press, and the outlet E of the static pressure filter is connected to the inlet A of the sedimentation mother liquor storage tank to discharge the filtrate filtered by the static pressure filter.

[0057] A further technical solution of the present invention is as follows: the carbonation synthesis component further includes a shell-and-tube heat exchanger B located between the bottom liquid outlet of the packed tower A and the solution inlet of the Venturi mixer; the shell-and-tube heat exchanger B is provided with a cooling water inlet, a cooling water outlet, an ammonium carbonate solution inlet, and an ammonium carbonate solution outlet; the ammonium carbonate solution inlet of the shell-and-tube heat exchanger B is connected to the bottom liquid outlet of the packed tower A, and the ammonium carbonate solution outlet of the shell-and-tube heat exchanger B is connected to the solution inlet of the Venturi mixer.

[0058] A further technical solution of the present invention is as follows: Pump A is installed on the pipeline between the thickener and the plate and frame filter press; Pump B is installed on the pipeline between the plate and frame filter press and the static pressure filter; Pump C is installed on the pipeline between the second port of the three-way valve A and the ammonia water reflux port of the stripping tower; Pump D is installed on the pipeline between the third port of the three-way valve A and the ammonia water storage tank; Pump E is installed on the pipeline between the fourth port of the three-way valve B and the mother liquor alkali inlet of the stripping tower; Pump F is installed on the pipeline between the eighth port of the three-way valve C and the bottom liquid reflux port of the stripping tower; Pump G is connected to the pipeline connected to the tube side outlet of the shell-and-tube heat exchanger A; Pump H is installed on the pipeline between the ammonium carbonate solution inlet of the shell-and-tube heat exchanger B and the bottom liquid outlet of the packed tower A; and Pump I is installed on the pipeline between the dilute nitric acid storage tank and the dilute nitric acid inlet of the packed tower B.

[0059] A further technical solution of the present invention is as follows: a flow control valve A is provided on the pipeline between the steam generator and the steam inlet of the stripping tower; a flow control valve B is provided on the pipeline between the alkali storage tank and the fifth port of the three-way valve B; a flow control valve C is provided on the pipeline between the outlet A of the precipitated mother liquor storage tank and the shell-side inlet of the shell-and-tube heat exchanger; and a flow control valve D is provided on the pipeline between the inlet of the carbon dioxide vaporizer and the liquid carbon dioxide storage tank.

[0060] Compared with the prior art, the present invention has the following advantages:

[0061] 1. It recovers the ammonium diuranate precipitate mother liquor in the uranium purification process, converts the fixed ammonia in it into free ammonia, prepares ammonia water, and then synthesizes the ammonia water with carbon dioxide to prepare ammonium carbonate solution. The ammonium carbonate solution can be returned to the uranium purification process as a crystallizing agent, thereby reducing the production cost of uranium purification.

[0062] 2. The recycling process is simple and easy to operate, and does not produce difficult-to-treat precipitates. The sodium nitrate solution, a byproduct of the recycling process, can be used for further recovery of nitrate ions or discharged under the premise of meeting environmental protection requirements; the treatment methods are diverse and easy to implement.

[0063] The present invention will be further described below with reference to the figures and embodiments. Attached Figure Description

[0064] Figure 1 This is a schematic diagram of the structure of the present invention;

[0065] Figure 2 This is a schematic diagram of the solid-liquid separation component in this invention;

[0066] Figure 3 This is a diagram showing the connection relationships of the components other than the solid-liquid separation component in this invention.

[0067] Figure 4 for Figure 3 Enlarged view of part A;

[0068] Figure 5 for Figure 3 Enlarged view of part B;

[0069] Figure 6 for Figure 3 Enlarged view of part C;

[0070] Figure 7 for Figure 3 Enlarged view of part D;

[0071] Figure 8 for Figure 3 Enlarged view of part E.

[0072] Legend: Thickener 11; Plate and frame filter press 12; Static pressure filter 13; Stripping tower 21; Reboiler liquid chamber 211; Gas-liquid mass transfer chamber 212; Ammonia chamber 213; Ammonia outlet 214; Reboiler liquid outlet 215; Steam inlet 216; Reboiler liquid reflux port 217; Ammonia water reflux port 218; Mother liquor / alkali inlet 219; Steam generator 22; Condenser 23; Gas phase inlet 231; Liquid phase outlet 232; Non-condensable gas outlet 233; First port 241; Second port 242; Third port 243; Fourth port 251; Fifth port 252; Sixth port 253; Seventh port 261; Eighth port 262; Ninth port 263; Shell and tube heat exchanger A27; Packed tower A31; Bottom liquid chamber 311; Carbonization synthesis chamber 312; Tail gas Chamber 313; Deionized water inlet 314; Tail gas outlet 315; Bottom liquid outlet 316; Gas-liquid mixing inlet 317; Ammonia inlet 318; Venturi mixer 32; Solution inlet 321; Gas inlet 322; Gas-liquid mixing outlet 323; Carbon dioxide vaporizer 33; Liquid carbon dioxide storage tank 34; Tenth port 351; Eleventh port 352; Twelfth port 353; Shell-and-tube heat exchanger B36; Precipitated mother liquor storage tank 41; Alkali storage tank 42; Ammonia storage tank 43; Ammonium carbonate solution storage tank 44; Packed tower B51; Liquid phase chamber 511; Packed absorption chamber 512; Gas phase chamber 513; Non-condensable gas outlet 514; Dilute nitric acid inlet 515; Non-condensable gas inlet 516; Tail gas inlet 517; Ammonium nitrate solution outlet 518; Dilute nitric acid storage tank 52. Detailed Implementation

[0073] Example 1:

[0074] like Figure 1-8 As shown, the crystallizer preparation system based on ammonium diuranate precipitate mother liquor includes a solid-liquid separation component, a deammoniation component, a carbonization synthesis component, a storage tank component, and a tail gas treatment component.

[0075] The solid-liquid separation assembly includes a thickener 11, a plate and frame filter press 12, and a static pressure filter 13. The thickener 11 has a separation chamber inside, and an overflow port on its upper side wall for discharging the clarified liquid from the upper part of the separation chamber. The thickener 11 also has an underflow port at its bottom for discharging the concentrated slurry from the lower part of the separation chamber. The plate and frame filter press 12 has an inlet D and an outlet D. The inlet D of the plate and frame filter press 12 is connected to the overflow port of the thickener 11 to receive the clarified liquid discharged from the thickener 11. The static pressure filter 13 has an inlet E and an outlet E. The inlet E of the static pressure filter 13 is connected to the outlet E of the plate and frame filter press 12 to receive the filtrate discharged from the plate and frame filter press 12. The outlet E of the static pressure filter 13 is used to discharge the filtrate filtered by the static pressure filter 13.

[0076] The solid-liquid separation assembly is used to remove the solid phase from the solution after the reaction. The filtration precision of the thickener 11, plate and frame filter press 12, and static pressure filter 13 increases sequentially, forming a three-stage filtration system from coarse to fine. The thickener 11 is used to separate the solid and liquid phases of the product after the reaction of uranyl nitrate (UNH) and ammonium hydroxide (NH4OH), removing most of the solid phase. The liquid phase flows into the plate and frame filter press 12. The solid phase is ammonium diuranate ((NH4)2U2O7), and the liquid phase is the precipitate mother liquor (mainly ammonium nitrate (NH4NO3) solution). The plate and frame filter press 12 is used to retain the residual fine crystals (mainly ammonium diuranate and uranium oxide impurities) in the precipitate mother liquor. The resulting liquid phase flows into the static pressure filter 13. The static pressure filter 13, also known as an open filter, is used to perform the finest inspection and filtration of the mother liquor, further filtering out the fine crystals (mainly ammonium diuranate and uranium oxide impurities) remaining in the mother liquor, so that the uranium content of the mother liquor discharged from the static pressure filter 13 is less than 15 mg / L, and the suspended solids ss < 200 mg / L.

[0077] The ammonia removal assembly includes a stripping tower 21, a steam generator 22, a condenser 23, a three-way valve A, a three-way valve B, and a three-way valve C. The stripping tower 21 has, from bottom to top, a bottom liquid chamber 211, a gas-liquid mass transfer chamber 212, and an ammonia chamber 213 connected in sequence. The top of the stripping tower 21 has an ammonia outlet 214 connected to the ammonia chamber 213. The bottom of the stripping tower 21 has a bottom liquid outlet 215 connected to the bottom liquid chamber 211. The side wall of the stripping tower 21 has a vapor inlet 216 connected to the junction of the bottom liquid chamber 211 and the gas-liquid mass transfer chamber 212. The side wall of the stripping tower 21 has a bottom liquid reflux port 217 connected to the junction of the bottom liquid chamber 211 and the gas-liquid mass transfer chamber 212. The side wall of the stripping tower 21 has an ammonia water reflux port 218 connected to the junction of the gas-liquid mass transfer chamber 212 and the ammonia chamber 213. The side wall of the stripping tower 21 has a mother liquor alkali inlet 219 connected to the gas-liquid mass transfer chamber 212. The steam generator 22 is connected to the steam inlet 216 of the stripping tower 21. The condenser 23 is equipped with a gas phase inlet 231, a liquid phase outlet 232, and a non-condensable gas outlet 233. The gas phase inlet 231 of the condenser 23 is connected to the ammonia outlet 214 of the stripping tower 21. The three-way valve A has a first port 241, a second port 242, and a third port 243. The first port 241 of the three-way valve A is connected to the liquid phase outlet 232 of the condenser 23. The second port 242 of the three-way valve A is connected to the ammonia water return port 218 of the stripping tower 21. The third port 243 of the three-way valve A is used to output ammonia water. The three-way valve B has a fourth port 251, a fifth port 252, and a sixth port 253. The fourth port 251 of the three-way valve B is connected to the mother liquor / alkali inlet 219 of the stripping tower 21. The fifth port 252 of the three-way valve B is used to receive alkali, and the sixth port 253 of the three-way valve B is used to receive mother liquor. The three-way valve C is equipped with a seventh port 261, an eighth port 262, and a ninth port 263. The seventh port 261 of the three-way valve C is connected to the bottom liquid outlet 215 of the stripping tower 21, the eighth port 262 of the three-way valve C is connected to the bottom liquid reflux port 217 of the stripping tower 21, and the ninth port 263 of the three-way valve C is used to discharge the bottom liquid.

[0078] The ammonia removal assembly is used to convert fixed ammonia in the mother liquor into free ammonia. On one hand, high-temperature steam (100°C) produced by the steam generator 22 enters the gas-liquid mass transfer chamber 212 of the stripping tower 21 through a pipe and steam inlet 216, and then flows upwards. On the other hand, sodium hydroxide (NaOH) solution in the alkali storage tank 32 enters the gas-liquid mass transfer chamber 212 of the stripping tower 21 sequentially through a pipe, the fifth port 252 of the three-way valve B, the fourth port 251 of the three-way valve B, and the mother liquor alkali inlet 219 of the stripping tower 21, and then is sprayed downwards. Furthermore, the mother liquor (NH4NO3 solution) in the mother liquor storage tank 31 enters the gas-liquid mass transfer chamber 212 of the stripping tower 21 sequentially through a pipe, the sixth port 253 of the three-way valve B, the fourth port 251 of the three-way valve B, and the mother liquor alkali inlet 219 of the stripping tower 21, and then is sprayed downwards. In the gas-liquid mass transfer chamber 212 of the stripping tower 21, upward-flowing water vapor comes into countercurrent contact with the downward-sprayed mixed liquid (the mixed liquid is obtained by mixing sodium hydroxide solution and precipitate mother liquor), and gas-liquid mass transfer occurs, resulting in the following chemical reactions: The sodium nitrate solution and ammonium hydroxide solution produced by the reaction flow downwards and collect in the bottom liquid chamber 211 of the stripping tower, forming the bottom liquid. In the bottom liquid chamber 211 of the stripping tower 21, ammonium hydroxide decomposes endothermally, undergoing the following decomposition reaction: The water produced by decomposition remains in the liquid chamber 211 of the bottom of the column, while the ammonia gas produced by decomposition flows upward and is discharged to the outside of the stripping column 21 through the gas-liquid mass transfer chamber 212, the ammonia gas chamber 213, and the ammonia gas outlet 214. Therefore, the main component of the bottom liquid is sodium nitrate, with a small amount of ammonium hydroxide to be decomposed. Based on the above two reactions, the fixed ammonia in the precipitate mother liquor is converted into free ammonia.

[0079] The carbonization synthesis assembly includes a packed tower A31, a venturi mixer 32, a carbon dioxide vaporizer 33, a liquid carbon dioxide storage tank 34, and a three-way valve D. The packed tower A31 has, from bottom to top, a bottom liquid chamber 311, a carbonization synthesis chamber 312, and a tail gas chamber 313. A water spraying component is provided at the junction of the carbonization synthesis chamber 312 and the tail gas chamber 313 inside the packed tower A31. The water spraying component is used to spray water mist into the carbonization synthesis chamber 312. A deionized water inlet 314 is provided on the side wall of the packed tower A31, which is connected to the water spraying component. A tail gas outlet 315 is provided at the top of the packed tower A31, which is connected to the tail gas chamber 313. A bottom liquid outlet 316 is provided at the bottom of the packed tower A31, which is connected to the bottom liquid chamber 311. A gas-liquid mixing inlet 317 is provided on the side wall of the packed tower A31, which is connected to the junction of the bottom liquid chamber 311 and the carbonization synthesis chamber 312. An ammonia water inlet 318 is provided on the side wall of the packed tower A31, which is connected to the carbonization synthesis chamber 312. The Venturi mixer 32 has a solution inlet 321 and a gas inlet 322 at its upper end, and a gas-liquid mixing outlet 323 at its lower end, which is connected to the gas-liquid mixing inlet 317 of the packed tower A31. The carbon dioxide vaporizer 33 has a liquid inlet and a gas outlet at both ends. The liquid inlet is connected to the liquid carbon dioxide storage tank 34, and the gas outlet is connected to the gas inlet 322 of the Venturi mixer 32. The three-way valve D has a tenth port 351, an eleventh port 352, and a twelfth port 353. The tenth port 351 of the three-way valve D is connected to the bottom liquid outlet 316 of the packed tower A31, and the eleventh port 352 of the three-way valve D is connected to the solution inlet 321 of the Venturi mixer 32.

[0080] The carbonization synthesis component is used to carbonize ammonia water. On one hand, ammonia water prepared by the deammoniation component enters the carbonization synthesis chamber 312 of packed tower A31 through the ammonia water inlet 318. On the other hand, liquid carbon dioxide stored in the liquid carbon dioxide storage tank 34 is vaporized by the carbon dioxide vaporizer 33 and then sequentially enters the carbonization synthesis chamber 312 of packed tower A31 through the Venturi mixer 32 and the gas-liquid mixing inlet 317, where it undergoes sufficient contact and the following chemical reaction occurs: The ammonium carbonate solution produced by the reaction flows downwards and eventually collects in the bottom liquid chamber 311 of the packed tower A31. The water mist sprayed by the water spray assembly can form a water seal between the carbonation synthesis chamber 312 and the tail gas chamber 313 of the packed tower A31, which is used to dissolve the volatilized ammonia gas and prevent ammonia gas from entering the tail gas chamber 313 and being discharged through the tail gas chamber 313. The ammonium carbonate solution discharged from the bottom liquid outlet 316 of the packed tower A31 is sampled and the ammonium carbonate concentration is tested: 1. If the ammonium carbonate concentration is lower than 350 g / L, it is judged as an unqualified ammonium carbonate solution. Then, the tenth port 351 and the eleventh port 352 of the three-way valve D are connected, so that the ammonium carbonate solution discharged from the bottom liquid outlet 316 of the packed tower A31 passes through the three-way valve D, the Venturi mixer 32 and the gas-liquid mixing inlet 317 of the packed tower A31 in sequence and returns to the carbonation synthesis chamber 312 of the packed tower A31 for concentration treatment. 2. If the ammonium carbonate concentration reaches 350 g / L, it is determined to be a qualified ammonium carbonate solution. Then, the tenth port 351 and the twelfth port 353 of the three-way valve D are connected so that the ammonium carbonate solution discharged from the bottom liquid outlet 316 of the packed tower A31 is input into the ammonium carbonate solution storage tank 44 through the three-way valve D for storage and later use.

[0081] The storage tank assembly includes a mother liquor storage tank 41, an alkali storage tank 42, an ammonia storage tank 43, and an ammonium carbonate solution storage tank 44. The mother liquor storage tank 41 has an inlet A and an outlet A. The inlet A of the mother liquor storage tank 41 is connected to the static pressure filter 13, and the outlet A of the mother liquor storage tank 41 is connected to the sixth port of the three-way valve B. The alkali storage tank 42 is connected to the fifth port of the three-way valve B. The ammonia storage tank 43 has an inlet C and an outlet C. The inlet C of the ammonia storage tank 43 is connected to the third port 243 of the three-way valve A, and the outlet C of the ammonia storage tank 43 is connected to the ammonia inlet 318 of the packed tower A31. The ammonium carbonate solution storage tank 44 is connected to the twelfth port 353 of the three-way valve D.

[0082] The exhaust gas treatment assembly includes a packed tower B51 and a dilute nitric acid storage tank 52. Inside the packed tower B51, from bottom to top, are a liquid phase chamber 511, a packed absorption chamber 512, and a gas phase chamber 513. A spray component is located at the junction of the packed absorption chamber 512 and the gas phase chamber 513 inside the packed tower B51. The spray component is used to spray atomized dilute nitric acid into the packed absorption chamber 512. The top of the packed tower B51 has a non-condensable gas outlet 514 connected to the gas phase chamber 513. A dilute nitric acid inlet 515 connected to the spray component is located on the side wall of the packed tower B51. A non-condensable gas inlet 516 connected to the junction of the liquid phase chamber 511 and the packed absorption chamber 512 is located on the side wall of the packed tower B51. An exhaust gas inlet 517 connected to the junction of the liquid phase chamber 511 and the packed absorption chamber 512 is located on the side wall of the packed tower B51. The bottom of the packed tower B51 has an ammonium nitrate solution outlet 518 connected to the liquid phase chamber 511. The non-condensable gas inlet 516 of packed tower B51 is connected to the non-condensable gas outlet 233 of condenser 23, and the tail gas inlet 517 of packed tower B51 is connected to the tail gas outlet 315 of packed tower A31. The dilute nitric acid storage tank 5 is connected to the dilute nitric acid inlet 515 of packed tower B5.

[0083] The exhaust gas treatment assembly is used to treat the non-condensable gases (mainly composed of ammonia) discharged from the top of stripping tower 21 and packed tower A31. The non-condensable gases discharged from the ammonia outlet 214 of stripping tower 21 pass sequentially through the gas phase inlet 231 of condenser 23, the non-condensable gas outlet 233 of condenser 23, and the non-condensable gas inlet 516 of packed tower B51, entering the packing absorption chamber 512 of packed tower B51 and flowing upwards. The exhaust gas discharged from the exhaust gas outlet 315 of packed tower A31 passes through the exhaust gas inlet 517 of packed tower B51 and enters the packing absorption chamber 512 of packed tower B51, flowing upwards. The dilute nitric acid in the dilute nitric acid storage tank 52 enters the spray component of packed tower B51 through the dilute nitric acid inlet 515 of packed tower B51 and is sprayed downwards. The upward-flowing ammonia gas comes into countercurrent contact with the downward-sprayed dilute nitric acid, resulting in gas-liquid mass transfer and the following chemical reaction: The ammonium nitrate solution generated by the reaction flows downward and collects in the liquid phase chamber 511. The ammonium nitrate solution can then be sent back to the deammoniation unit for recycling.

[0084] Preferably, the ammonia removal assembly also includes a shell-and-tube heat exchanger A27 located between the mother liquor storage tank 41 and the three-way valve C. The shell-and-tube heat exchanger A27 has an internal tube cavity and a shell cavity, and externally has a shell-side inlet, a shell-side outlet, a tube-side inlet, and a tube-side outlet. The shell-side inlet and outlet are both connected to the shell cavity, and the tube-side inlet and outlet are both connected to the tube cavity. The shell-side inlet of the shell-and-tube heat exchanger A27 is connected to the outlet A of the mother liquor storage tank 41, the shell-side outlet is connected to the sixth port 253 of the three-way valve B, the tube-side inlet is connected to the ninth port 263 of the three-way valve C, and a pipe for discharging the bottom liquid is connected to the tube-side outlet of the shell-and-tube heat exchanger A27. Shell-and-tube heat exchanger A27 is used to recover residual heat from the bottom liquid in stripping tower 21 and preheat the mother liquor, thereby reducing the energy consumption of stripping tower 21.

[0085] Preferably, the carbonation synthesis assembly further includes a shell-and-tube heat exchanger B36 located between the bottom liquid outlet 316 of the packed tower A31 and the solution inlet 321 of the Venturi mixer 32. The shell-and-tube heat exchanger B36 has a cooling water inlet, a cooling water outlet, an ammonium carbonate solution inlet, and an ammonium carbonate solution outlet. The ammonium carbonate solution inlet of the shell-and-tube heat exchanger B36 is connected to the bottom liquid outlet 316 of the packed tower A31, and the ammonium carbonate solution outlet of the shell-and-tube heat exchanger B36 is connected to the solution inlet 321 of the Venturi mixer 32. The shell-and-tube heat exchanger B36 is used to continuously cool the ammonium carbonate solution, thereby maintaining a suitable reaction temperature inside the packed tower A31, which helps the exothermic reaction occurring inside the packed tower A31 to proceed continuously and uninterruptedly.

[0086] Preferably, pump A is installed on the pipeline between thickener 11 and plate and frame filter press 12, and pump B is installed on the pipeline between plate and frame filter press 12 and static pressure filter 13. Pump C is installed on the pipeline between the second port 242 of three-way valve A and the ammonia reflux port 218 of stripping tower 21, pump D is installed on the pipeline between the third port 243 of three-way valve A and ammonia storage tank 33, and pump E is installed on the pipeline between the fourth port 251 of three-way valve B and the mother liquor alkali inlet 219 of stripping tower 21. Pump F is installed on the pipeline between the eighth port 262 of three-way valve C and the bottom liquid reflux port 217 of stripping tower 21. Pump G is connected to the pipeline connected to the tube side outlet of shell and tube heat exchanger. Pump H is installed on the pipeline between the outlet E of static pressure filter 13 and the inlet A of sedimentation mother liquor storage tank 31, and pump I is installed on the pipeline between dilute nitric acid storage tank 52 and dilute nitric acid inlet 515 of packed tower B51. The aforementioned pumps are configured to provide the power for the flow of liquid between the various devices.

[0087] Preferably, a flow control valve A is installed on the pipeline between the steam generator 22 and the steam inlet 216 of the stripping tower 21; a flow control valve B is installed on the pipeline between the alkali storage tank 32 and the fifth port 252 of the three-way valve B; and a flow control valve C is installed on the pipeline between the outlet A of the precipitate mother liquor storage tank 31 and the shell-side inlet of the shell-and-tube heat exchanger 27. A flow control valve D is installed on the pipeline between the inlet of the carbon dioxide vaporizer 33 and the liquid carbon dioxide storage tank 34. Flow control valve A is used to control the amount of high-temperature steam (100°C) entering the stripping tower 21, thereby controlling the temperature of the bottom liquid inside the stripping tower 21. When the bottom liquid temperature is controlled within a suitable range (95-105°C), it is beneficial for the decomposition reaction of ammonium hydroxide. Flow control valve B is used to control the amount of sodium hydroxide solution entering the stripping tower 21, thereby controlling the reaction efficiency inside the stripping tower 21. Flow control valve C is used to control the amount of precipitate mother liquor entering the stripping tower 21, thereby controlling the reaction efficiency inside the stripping tower 21.

[0088] Briefly describe the workflow of this invention:

[0089] The crystallizing agent preparation system based on ammonium diuranate precipitate mother liquor is used to recover ammonium diuranate precipitate mother liquor from the uranium purification process to prepare ammonium carbonate solution. The operation is as follows:

[0090] S01, Removal of solid phase:

[0091] 1. Thickener 11 performs preliminary solid-liquid separation on the product of the reaction between uranyl nitrate and ammonium hydroxide. The solid phase ammonium diuranate is discharged and enters the subsequent process of uranium purification to prepare ammonium tricarbonate. The liquid phase precipitate mother liquor flows into plate and frame filter press 12 through pipeline, waiting for further solid-liquid separation.

[0092] 2. The plate and frame filter press 12 retains the fine crystals remaining in the precipitated mother liquor. The liquid phase obtained after retention flows into the static pressure filter 13 for further solid-liquid separation.

[0093] 3. The static pressure filter 13 checks and filters the mother liquor, further filtering out the fine crystals remaining in the mother liquor, so that the uranium content in the mother liquor discharged from the static pressure filter 13 is <15mg / L, and the suspended solids SS is <200mg / L.

[0094] 4. The precipitated mother liquor discharged from the static pressure filter enters the precipitated mother liquor storage tank 31 and is left to stand for 3 to 5 months to reduce its radioactivity to the level of natural uranium.

[0095] In the second and third sub-steps of this process, the fine crystals contain ammonium diuranate and uranium oxide impurities.

[0096] In the second and third sub-steps of this process, the filter residue filtered by the plate and frame filter press 12 and the static pressure filter 13 is returned to the thickener 11 to prevent uranium loss.

[0097] In the third sub-step of this process, if the precipitated mother liquor discharged from the static pressure filter 13 does not meet the requirements of uranium content <15mg / L and suspended solids (SS) <200mg / L, then check whether the filtration functions of the thickener 11, plate and frame filter press 12, and static pressure filter 13 are normal. After the filtration functions of the thickener 11, plate and frame filter press 12, and static pressure filter 13 are adjusted to normal, the precipitated mother liquor is returned to the thickener 11 to remove the solid phase again.

[0098] SO2, fixed ammonia is converted into free ammonium:

[0099] 1. After standing and storing, the precipitated mother liquor is fed into the shell cavity of the shell-and-tube heat exchanger 27. The precipitated mother liquor in the shell cavity exchanges heat with the bottom liquid in the tube cavity of the shell-and-tube heat exchanger, and the temperature rises. Then, it enters the gas-liquid mass transfer chamber 212 of the stripping tower 21 through the sixth port 253 of the three-way valve B, the fourth port 251 of the three-way valve B and the mother liquor alkali inlet 219 of the stripping tower 21, and is sprayed downward.

[0100] 2. The sodium hydroxide solution stored in the alkali storage tank 32 enters the gas-liquid mass transfer chamber 212 of the stripping tower 21 through the fifth port 252 of the three-way valve B, the fourth port 251 of the three-way valve B and the mother liquor alkali inlet 219 of the stripping tower 21, and is sprayed downward.

[0101] 3. The high-temperature steam produced by the steam generator 22 enters the gas-liquid mass transfer chamber 212 of the stripping tower 21 through the steam inlet 216 and flows upward.

[0102] 4. In the gas-liquid mass transfer chamber 212 of the stripping tower 21, the upward-flowing water vapor comes into countercurrent contact with the downward-sprayed mixed liquid (the mixed liquid is obtained by mixing sodium hydroxide solution and precipitate mother liquor), and gas-liquid mass transfer occurs, resulting in the following chemical reactions: The sodium nitrate solution and ammonium hydroxide solution produced by the reaction flow downwards and collect in the bottom liquid chamber 211 of the stripping tower, forming the bottom liquid. In the bottom liquid chamber 211 of the stripping tower 21, ammonium hydroxide decomposes endothermally, undergoing the following decomposition reaction: The water produced by decomposition remains in the liquid chamber 211 of the tower bottom, while the ammonia produced by decomposition flows upward and is discharged to the outside of the stripping tower 21 through the gas-liquid mass transfer chamber 212, the ammonia chamber 213 and the ammonia outlet 214 in sequence. Based on the above two reactions, the fixed ammonia in the precipitated mother liquor is converted into free ammonia.

[0103] Steps 1, 2, and 3 of this process are performed simultaneously.

[0104] In the second sub-step of this process, the mass fraction of the sodium hydroxide solution is 20-50%.

[0105] In the third sub-step of this process, the temperature of the high-temperature steam is between 95-100℃.

[0106] In the fourth sub-step of this process, the main component of the bottom liquid is sodium nitrate, and the secondary component is ammonium hydroxide that has not yet decomposed.

[0107] In the fourth sub-step of this process, the temperature of the ammonia chamber 213 of the stripping tower 21 is controlled between 90-100℃ (the temperature of the ammonia chamber 213 can be controlled by adjusting the amount of high-temperature steam entering the stripping tower 21), the temperature of the bottom liquid in the bottom liquid chamber 211 of the stripping tower 21 is controlled between 95-105℃ (the temperature of the bottom liquid can be controlled by adjusting the amount of high-temperature steam entering the stripping tower 21), and the pH of the bottom liquid in the bottom liquid chamber 211 of the stripping tower 21 is controlled between 10-13 (the pH of the bottom liquid can be controlled by adjusting the amount of sodium hydroxide solution entering the tower).

[0108] S03, treatment of bottom liquid in the tower:

[0109] The liquid in the bottom chamber 211 of the stripping tower 21 is sampled and the ammonia nitrogen content is tested.

[0110] If [NH4±N] < 15 mg / L, then connect the seventh port 261 and the ninth port 263 of the three-way valve C. The bottom liquid in the bottom liquid chamber 211 of the stripping tower 21 is discharged from the bottom liquid outlet 215 of the stripping tower 21, and then enters the tube cavity of the shell-and-tube heat exchanger 27 through the three-way valve C. The bottom liquid in the tube cavity of the shell-and-tube heat exchanger 27 exchanges heat with the precipitated mother liquor in the shell cavity of the shell-and-tube heat exchanger 27 to preheat the precipitated mother liquor. The bottom liquid after heat exchange is discharged from the tube cavity of the shell-and-tube heat exchanger 27 as wastewater or enters the wastewater treatment process to recover nitrate.

[0111] If [NH4±N]≥15mg / L, then connect the seventh port 261 and the eighth port 262 of the three-way valve C. The liquid in the bottom chamber 211 of the stripping tower 21 will be discharged from the bottom liquid outlet 215 of the stripping tower 21, and then returned to the bottom liquid chamber 211 of the stripping tower 21 through the three-way valve C and the bottom liquid reflux port 217 of the stripping tower 21 to continue the decomposition reaction of ammonium hydroxide.

[0112] S04, collecting ammonia water:

[0113] 1. The gas in the ammonia chamber 213 of the stripping tower 21 is a mixture of ammonia, water vapor, and other non-condensable gases. After the mixed gas is discharged from the ammonia outlet 214 of the stripping tower 21, it enters the interior of the condenser 23 through the gas phase inlet 231 of the condenser 23, where it condenses to form ammonia water. The reactions that occur during the condensation process are as follows: Ammonia water is discharged through the liquid phase outlet 232 of condenser 23, and non-condensable gas is discharged from the non-condensable gas outlet 233 of condenser 23, and then enters the waste gas treatment process to convert the free ammonium in it into fixed ammonia.

[0114] 2. Sample the ammonia water discharged from the liquid phase outlet 232 of condenser 23 and test the ammonia water concentration;

[0115] If the mass fraction of ammonia water is between 15-20%, then the first port 241 and the third port 243 of the three-way valve A are connected, and the ammonia water discharged from the liquid phase outlet 232 of the condenser 23 enters the ammonia water storage tank 33 through the three-way valve A for storage.

[0116] If the mass fraction of ammonia is less than 15%, then the first port 241 of the three-way valve A is connected to the second port 242. The ammonia discharged from the liquid phase outlet 232 of the condenser 23 returns to the gas-liquid mass transfer chamber 212 of the stripping tower 21 through the three-way valve A and the ammonia return port 218 of the stripping tower 21, and undergoes the following decomposition reaction: At the same time, the supply of high-temperature water vapor to the stripping tower 21 is reduced, thereby increasing the ammonia concentration in the ammonia chamber 213 of the stripping tower 21.

[0117] If the mass fraction of ammonia water is higher than 20%, then the first port 241 and the second port 242 of the three-way valve A are connected. The ammonia water discharged from the liquid phase outlet 232 of the condenser 23 returns to the gas-liquid mass transfer chamber 212 of the stripping tower 21 through the three-way valve A and the ammonia water return port 218 of the stripping tower 21, and undergoes the following decomposition reaction: At the same time, the supply of high-temperature steam to the stripping tower 21 is increased, thereby reducing the ammonia concentration in the ammonia chamber 213 of the stripping tower 21.

[0118] S05, ammonia carbonization treatment:

[0119] 1. The ammonia water stored in the ammonia water storage tank 43 is discharged and enters the carbonization synthesis chamber 312 of the packed tower A31 through the ammonia water inlet 318;

[0120] 2. The liquid carbon dioxide stored in the liquid carbon dioxide storage tank 34 is vaporized by the carbon dioxide vaporizer 33 and then enters the carbonization synthesis chamber 312 of the packed tower A31 through the gas inlet 322 of the Venturi mixer 32, the gas-liquid mixing outlet 323 of the Venturi mixer 32 and the gas-liquid mixing inlet 317 of the packed tower A31 in sequence.

[0121] 3. Ammonia and carbon dioxide come into full contact in the carbonization synthesis chamber 312 of packed tower A31, and the following chemical reaction occurs: The ammonium carbonate solution produced by the reaction flows downward and collects in the bottom liquid chamber 311 of the packed tower A31.

[0122] 4. The water spraying component sprays water mist into the carbonization synthesis chamber 312, thereby forming a water seal between the carbonization synthesis chamber 312 and the tail gas chamber 313 of the packed tower A31. This seal is used to dissolve the ammonia gas volatilized from the ammonia water and prevent the ammonia gas from entering the tail gas chamber 313 and being discharged through the tail gas chamber 313.

[0123] 5. Sample and test the ammonium carbonate concentration of the ammonium carbonate solution discharged from the bottom liquid outlet 316 of packed tower A31. The following two cases are handled: a) If the ammonium carbonate concentration is lower than 350 g / L, it is determined to be an unqualified ammonium carbonate solution. Then, connect the tenth port 351 and the eleventh port 352 of the three-way valve D, so that the ammonium carbonate solution discharged from the bottom liquid outlet 316 of packed tower A31 passes through the three-way valve D, the Venturi mixer 32 and the gas-liquid mixing inlet 317 of packed tower A31 and returns to the carbonation synthesis chamber 312 of packed tower A31 for concentration treatment; b) If the ammonium carbonate concentration reaches 350 g / L, it is determined to be a qualified ammonium carbonate solution. Then, connect the tenth port 351 and the twelfth port 353 of the three-way valve D, so that the ammonium carbonate solution discharged from the bottom liquid outlet 316 of packed tower A31 enters the ammonium carbonate solution storage tank 44 through the three-way valve D for storage and later use.

[0124] Steps 1 and 2 of this process are performed simultaneously, as are steps 3 and 4.

[0125] S06, Exhaust gas treatment:

[0126] 1. The non-condensable gas discharged from the ammonia outlet 214 of the stripping tower 21 passes sequentially through the gas phase inlet 231 of the condenser 23, the non-condensable gas outlet 233 of the condenser 23, and the non-condensable gas inlet 516 of the packed tower B51, and enters the packing absorption chamber 512 of the packed tower B51, flowing upward.

[0127] 2. The exhaust gas discharged from the exhaust outlet 315 of the packed tower A31 enters the packing absorption chamber 512 of the packed tower B51 through the exhaust inlet 517 of the packed tower B51 and flows upward.

[0128] 3. The dilute nitric acid in the dilute nitric acid storage tank 52 enters the spray component of the packed tower B51 through the dilute nitric acid inlet 515 and is sprayed downwards;

[0129] 4. The upward-flowing ammonia gas comes into countercurrent contact with the downward-spraying dilute nitric acid, resulting in gas-liquid mass transfer and the following chemical reaction: The ammonium nitrate solution generated by the reaction flows downward and collects in the liquid phase cavity 511.

[0130] Steps 1, 2, and 3 in this process are performed simultaneously.

[0131] After this step is completed, the ammonium nitrate solution is sent back to the deammoniation unit for recycling.

Claims

1. A method for preparing a crystallizing agent based on ammonium diuranate precipitate mother liquor, characterized by: The method is used to recover the ammonium diuranate precipitate mother liquor in the uranium purification process and prepare an ammonium carbonate solution. The steps are as follows: S01, Removal of solid phase: a. The thickener performs preliminary solid-liquid separation on the product of the reaction between uranyl nitrate and ammonium hydroxide. The solid phase ammonium diuranate is discharged and enters the subsequent process of uranium purification to prepare ammonium tricarbonate. The liquid phase precipitate mother liquor flows into the plate and frame filter press through the pipeline, waiting for further solid-liquid separation. b. The plate and frame filter press retains the fine crystals remaining in the mother liquor. The liquid phase obtained after retention flows into the static pressure filter for further solid-liquid separation. c. The static pressure filter is used to check and filter the mother liquor, further filtering out the fine crystals remaining in the mother liquor, so that the uranium content in the mother liquor discharged from the static pressure filter is <15mg / L, and the suspended solids (SS) is <200mg / L. d. The mother liquor discharged from the static pressure filter enters the mother liquor storage tank and is left to stand for 3 to 5 months to reduce its radioactivity to the level of natural uranium. SO2, fixed ammonia is converted into free ammonium: a. After standing and storing, the precipitated mother liquor is fed into the shell cavity of shell-and-tube heat exchanger A. The precipitated mother liquor in the shell cavity exchanges heat with the bottom liquid in the tube cavity of shell-and-tube heat exchanger A, and the temperature rises. Then, it enters the gas-liquid mass transfer chamber of the stripping tower through the sixth port of the three-way valve B, the fourth port of the three-way valve B, and the mother liquor alkali inlet of the stripping tower, and is sprayed downward. b. The sodium hydroxide solution stored in the alkali storage tank enters the gas-liquid mass transfer chamber of the stripping tower through the fifth port of the three-way valve B, the fourth port of the three-way valve B, and the mother liquor alkali inlet of the stripping tower, and is sprayed downwards. c. The high-temperature steam produced by the steam generator enters the gas-liquid mass transfer chamber of the stripper through the steam inlet and flows upward. d. In the gas-liquid mass transfer chamber of the stripping tower, upward-flowing water vapor comes into countercurrent contact with the downward-sprayed mixed liquid, undergoing gas-liquid mass transfer and the following chemical reactions occur: The sodium nitrate solution and ammonium hydroxide solution produced by the reaction flow downwards and collect in the bottom liquid chamber of the tower to form the bottom liquid; In the bottom liquid chamber of the stripping column, ammonium hydroxide decomposes endothermally, undergoing the following decomposition reaction: ; The water produced by decomposition remains in the liquid chamber of the tower bottom, while the ammonia produced by decomposition flows upward and is discharged to the outside of the stripping tower through the gas-liquid mass transfer chamber, the ammonia chamber, and the ammonia outlet in sequence. Based on the above two reactions, the fixed ammonia in the precipitate mother liquor is converted into free ammonia. Steps a, b, and c of this step are performed simultaneously; in step d of this step, the mixed solution is obtained by mixing sodium hydroxide solution and the mother liquor of the precipitate. S03, treatment of bottom liquid in the tower: The liquid in the bottom chamber of the stripping tower was sampled and the ammonia nitrogen content was tested. If [NH4±N] < 15 mg / L, then connect the seventh and ninth ports of the three-way valve C. The bottom liquid in the stripping tower is discharged from the bottom liquid outlet of the stripping tower and then enters the tube cavity of the shell-and-tube heat exchanger through the three-way valve C. The bottom liquid in the tube cavity of the shell-and-tube heat exchanger exchanges heat with the precipitated mother liquor in the shell cavity of the shell-and-tube heat exchanger to preheat the precipitated mother liquor. The bottom liquid after heat exchange is discharged from the tube cavity of the shell-and-tube heat exchanger A as wastewater or enters the wastewater treatment process to recover nitrate. If [NH4±N]≥15mg / L, then connect the seventh and eighth ports of the three-way valve C. The liquid in the bottom chamber of the stripping tower will be discharged from the bottom liquid outlet of the stripping tower and then returned to the bottom liquid chamber of the stripping tower through the three-way valve C and the bottom liquid reflux port of the stripping tower to continue the decomposition reaction of ammonium hydroxide. S04, collecting ammonia water: a. The gas in the ammonia chamber of the stripping tower is a mixture of ammonia, water vapor, and other non-condensable gases. After the mixed gas is discharged from the ammonia outlet of the stripping tower, it enters the condenser through the gas phase inlet and condenses to form ammonia water. The reactions that occur during the condensation process are as follows: Ammonia water is discharged through the liquid phase outlet of the condenser, and non-condensable gas is discharged from the non-condensable gas outlet of the condenser. It then enters the waste gas treatment process to convert the free ammonium in it into fixed ammonia. b. Sample the ammonia water discharged from the liquid phase outlet of the condenser and test the ammonia water concentration; If the mass fraction of ammonia water is between 15-20%, then connect the first port and the third port of the three-way valve A, and the ammonia water discharged from the liquid phase outlet of the condenser will enter the ammonia water storage tank through the three-way valve A for storage. If the mass fraction of ammonia is less than 15%, then the first port of the three-way valve A is connected to the second port. The ammonia discharged from the liquid phase outlet of the condenser returns to the gas-liquid mass transfer chamber of the stripping tower through the three-way valve A and the ammonia return port of the stripping tower, where it undergoes the following decomposition reaction: At the same time, the supply of high-temperature steam to the stripping tower is reduced, thereby increasing the ammonia concentration in the ammonia chamber of the stripping tower. If the mass fraction of ammonia water is higher than 20%, then the first port and the second port of the three-way valve A are connected. The ammonia water discharged from the liquid phase outlet of the condenser returns to the gas-liquid mass transfer chamber of the stripping tower through the three-way valve A and the ammonia water return port of the stripping tower, and undergoes the following decomposition reaction: At the same time, the supply of high-temperature steam to the stripping tower is increased, thereby reducing the ammonia concentration in the ammonia chamber of the stripping tower. S05, ammonia carbonization treatment: a. The ammonia water stored in the ammonia water storage tank is discharged and enters the carbonization synthesis chamber of packed tower A through the ammonia water inlet of packed tower A; b. After being vaporized by the carbon dioxide vaporizer, the liquid carbon dioxide stored in the liquid carbon dioxide storage tank enters the carbonization synthesis chamber of the packed tower A through the gas inlet of the Venturi mixer, the gas-liquid mixing outlet of the Venturi mixer, and the gas-liquid mixing inlet of the packed tower A in sequence. c. Ammonia and carbon dioxide come into full contact in the carbonization and synthesis chamber of packed tower A, and the following chemical reaction occurs: The ammonium carbonate solution produced by the reaction flows downwards and collects in the bottom liquid chamber of packed tower A. d. The water spraying component sprays water mist into the carbonization synthesis chamber, thereby forming a water seal between the carbonization synthesis chamber and the tail gas chamber of the packed tower A. This seal is used to dissolve the ammonia gas volatilized from the ammonia water and prevent the ammonia gas from entering the tail gas chamber and being discharged through the tail gas chamber. e. Sample and test the ammonium carbonate solution discharged from the bottom liquid outlet of packed tower A. The following two scenarios are handled: Ⅰ. If the ammonium carbonate concentration is below 350 g / L, it is considered an unqualified ammonium carbonate solution. Connect the tenth and eleventh ports of the three-way valve D, allowing the ammonium carbonate solution discharged from the bottom liquid outlet of packed tower A to sequentially pass through the three-way valve D, the Venturi mixer, and the gas-liquid mixing inlet of packed tower A back into the carbonation synthesis chamber of packed tower A for concentration. Ⅱ. If the ammonium carbonate concentration reaches 350 g / L, it is considered a qualified ammonium carbonate solution. Connect the tenth and twelfth ports of the three-way valve D, allowing the ammonium carbonate solution discharged from the bottom liquid outlet of packed tower A to be input into the ammonium carbonate solution storage tank through the three-way valve D for later use. Steps a and b of this step are performed simultaneously, as are steps c and d of this step.

2. The method for preparing a crystallizer based on ammonium diuranate precipitate mother liquor as described in claim 1, characterized in that: The method also includes step S06, which follows step S05. S06, Exhaust gas treatment: a. The non-condensable gas discharged from the ammonia outlet of the stripping tower passes sequentially through the gas phase inlet of the condenser, the non-condensable gas outlet of the condenser, and the non-condensable gas inlet of the packed tower B, and enters the packing absorption chamber of the packed tower B, flowing upward. b. The exhaust gas discharged from the tail gas outlet of packed tower A enters the packing absorption chamber of packed tower B through the tail gas inlet of packed tower B and flows upward. c. The dilute nitric acid in the dilute nitric acid storage tank enters the spray component of the packed tower B through the dilute nitric acid inlet and is sprayed downwards. d. The upward-flowing ammonia gas comes into countercurrent contact with the downward-spraying dilute nitric acid, resulting in gas-liquid mass transfer and the following chemical reaction: The ammonium nitrate solution produced by the reaction flows downwards and collects in the liquid phase cavity; Steps a, b, and c in this process are performed simultaneously. After this step is completed, the ammonium nitrate solution collected in the liquid phase chamber of packed tower B is sent back to the deammoniation assembly for recycling.

3. The method for preparing a crystallizer based on ammonium diuranate precipitate mother liquor as described in claim 2, characterized in that: In sub-steps b and c of step S01, the fine crystals contain ammonium diuranate and uranium oxide impurities; the filter residue filtered by the plate and frame filter press and the static pressure filter are returned to the thickener to avoid uranium loss.

4. The method for preparing a crystallizer based on ammonium diuranate precipitate mother liquor as described in claim 3, characterized in that: In sub-step c of step S01, if the precipitated mother liquor discharged from the static pressure filter does not meet the requirements of uranium content <15mg / L and suspended solids SS <200mg / L, then check whether the filtration functions of the thickener, plate and frame filter press and static pressure filter are normal. After the filtration functions of the thickener, plate and frame filter press and static pressure filter are adjusted to normal, return the precipitated mother liquor to the thickener to remove the solid phase again.

5. The method for preparing a crystallizer based on ammonium diuranate precipitate mother liquor as described in claim 4, characterized in that: In step d of step S02, the temperature of the ammonia chamber in the stripping tower is controlled between 90-100℃. This temperature control can be achieved by adjusting the amount of high-temperature steam entering the stripping tower. The temperature of the bottom liquid in the bottom liquid chamber of the stripping tower is controlled between 95-105℃. This temperature control can be achieved by adjusting the amount of high-temperature steam entering the stripping tower. The pH of the bottom liquid in the bottom liquid chamber of the stripping tower is controlled between 10-13. This pH control can be achieved by adjusting the amount of sodium hydroxide solution entering the bottom liquid.

6. The method for preparing a crystallizer based on ammonium diuranate precipitate mother liquor as described in claim 5, characterized in that: In step b of the SO2 step, the mass fraction of the sodium hydroxide solution is 20-50%; in step c of the SO2 step, the temperature of the high-temperature steam is between 95-100℃.

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