Molten salt purification device and molten salt purification method

Abstract

The present invention relates to the technical field of molten salt purification, and provides a molten salt purification device and a molten salt purification method. The molten salt purification device includes a heating furnace, an insulation layer, a reactor, a sleeve, an air inlet and outlet device, and a crucible. The heating furnace is provided with multiple heating zones in the height direction, and each heating zone is separated by an insulation layer and can be individually temperature-controlled. The reactor is partially arranged in the heating furnace and extends into the multiple heating zones. The reactor is provided with a reaction chamber and a cavity port connected to the reaction chamber. The sleeve is placed in the reaction chamber from the cavity port and covers the cavity port. A placement chamber is provided in the sleeve. The air inlet and outlet device is connected to the placement chamber and is used to provide inert gas to the placement chamber. The crucible is placed in the placement chamber and is used to accommodate the molten salt to be purified. After heating and melting the molten salt to be purified, each heating zone can be controlled to slowly cool down from top to bottom so that the molten salt solidifies from top to bottom, completing the purification. Impurities will flow to the bottom of the crucible, thereby obtaining the purified molten salt in the upper layer. The structure is simple.

Description

Technical Field

[0001] The present invention relates to the technical field of molten salt purification, and in particular to a molten salt purification device and a molten salt purification method. Background Art

[0002] Dry reprocessing technology based on molten salt electrolysis is considered the most promising dry reprocessing technology for spent fuel. This process utilizes the difference in redox potentials between actinides (such as uranium (U) and plutonium (Pu)) and fragment elements in the molten salt system to separate and recover actinides through potential control. During this separation and recovery process, lanthanides and active fragment elements (such as Cs and Sr) accumulate in the molten salt, altering the physical and chemical properties of the system and generating large amounts of waste salt. Purification and reuse of the waste salt are crucial for both environmental and economic reasons. To achieve this and minimize radioactive waste, purification of the lanthanides and active fragment elements (such as Cs and Sr) in the waste molten salt is necessary. Localized condensation has proven to be an effective molten salt purification method for separating Cs and Sr from waste salt. However, most localized condensation devices rely on a robotic arm to move the crucible, heating zone, or condensation plate. This makes them relatively complex and cumbersome, making them difficult to operate and expensive. Furthermore, localized condensation devices require strict control of the precise temperature of the condensation plate, requiring the coupling of numerous thermocouples and sensors, resulting in a complex structure. Summary of the Invention

[0003] The present invention aims to solve at least one of the technical problems existing in the related art. To this end, the present invention proposes a molten salt purification device, which aims to simplify the structure and facilitate molten salt purification.

[0004] The invention also provides a molten salt purification method.

[0005] The molten salt purification device according to the first embodiment of the present invention includes:

[0006] A heating furnace, wherein the heating furnace is provided with multiple heating zones in the height direction, each adjacent heating zone is separated by a heat insulation layer, and each heating zone can be individually temperature-controlled;

[0007] A reactor, wherein a portion of the reactor is disposed in the heating furnace and extends into the multi-stage heating zone, the reactor being provided with a reaction chamber and a cavity opening communicating with the reaction chamber;

[0008] The sleeve is placed in the reaction chamber from the cavity opening and covers the cavity opening. The sleeve is provided with a placement cavity.

[0009] an air inlet and outlet device, the air inlet and outlet device being connected to the placement cavity and being used to provide inert gas to the placement cavity;

[0010] A crucible is placed in the placement cavity and is used to accommodate molten salt to be purified.

[0011] According to the molten salt purification device of the embodiment of the present invention, the molten salt to be purified is placed in a crucible, and the crucible is placed in the placement cavity of the sleeve, and the reaction environment conditions are provided by the sleeve. At the same time, the crucible is easily taken into and placed in the reaction cavity of the reactor through the sleeve. The reactor is installed in the heating furnace, and the sleeve is sealed at the cavity mouth of the reaction cavity to prevent the volatilization of the molten salt. The heating furnace is provided with multiple heating zones arranged in sequence along the height direction. Each heating zone can be individually temperature-controlled. The heating furnace can heat and melt the molten salt to be purified in the crucible. After the molten salt to be purified is heated and melted, each heating zone can be controlled to slowly cool down from top to bottom so that the molten salt solidifies from top to bottom, completing the purification. The impurities will flow to the bottom of the crucible, thereby obtaining the upper layer of purified molten salt. The structure is simple.

[0012] According to one embodiment of the present invention, the crucible extends in a height direction to cover and extend to each section of the heating zone.

[0013] According to one embodiment of the present invention, the heating range of each heating zone is 400° C. to 700° C.

[0014] According to an embodiment of the present invention, each heating zone is correspondingly provided with a temperature sensor, and the temperature sensor is located in the middle position of the heating zone in the height direction.

[0015] According to one embodiment of the present invention, the molten salt purification device includes a water cooling device, which is arranged around the top of the reactor and is equipped with cooling water.

[0016] According to one embodiment of the present invention, the air inlet and outlet device includes an air inlet pipe, an air outlet pipe and a vacuum pipe connected to the sleeve, and the air inlet pipe, the air outlet pipe and the vacuum pipe are all connected to the placement cavity.

[0017] According to one embodiment of the present invention, an end cover is provided on the outer wall of the sleeve, and the end cover seals the cavity opening.

[0018] According to one embodiment of the present invention, the end cover is provided with a threaded hole, and the end cover is connected to the reactor through the threaded hole.

[0019] The molten salt purification method according to the second embodiment of the present invention includes:

[0020] heating the heating furnace until the molten salt mixture in the crucible is melted;

[0021] The multi-stage heating zones are cooled section by section from top to bottom so that the molten salt in the crucible solidifies section by section.

[0022] According to one embodiment of the present invention, the step of gradually cooling the multi-stage heating zones from top to bottom includes:

[0023] The heating temperature of the multiple heating zones is gradually reduced to cool the heating zones. When the temperature of the heating zones is lower than the melting point of the molten salt, heating of the heating zones is stopped, and the heating temperature of the next heating zones is then reduced.

[0024] The molten salt purification method according to an embodiment of the present invention includes the above-mentioned molten salt purification device, and therefore has all the technical effects of the above-mentioned molten salt purification device, which will not be repeated here.

[0025] Additional aspects and advantages of the present invention will be set forth in part in the description which follows and, in part, will be obvious from the description which follows, or may be learned by practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or related technologies, the following briefly introduces the drawings required for use in the embodiments or related technical descriptions. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0027] Figure 1 Schematic diagram of the structure of the molten salt purification device provided by an embodiment of the present invention;

[0028] Figure 2 is a schematic cross-sectional view of a partial structure of a molten salt purification device provided by an embodiment of the present invention;

[0029] Figure 3 1 is a schematic top view of a partial structure of a molten salt purification device provided in an embodiment of the present invention;

[0030] Reference numerals:

[0031] 1. Heating furnace; 2. Reactor; 21. Reaction chamber; 3. Sleeve; 31. Placement chamber; 32. End cover; 4. Crucible; 51. Air inlet pipe; 52. Air outlet pipe; 53. Vacuum tube; 6. Water cooling device; 61. Water inlet; 62. Water outlet; 7. Heating zone; 8. Thermal insulation layer. DETAILED DESCRIPTION

[0032] The following embodiments of the present invention are described in further detail with reference to the accompanying drawings and examples. The following examples are used to illustrate the present invention but are not intended to limit the scope of the present invention.

[0033] In the description of the embodiments of the present invention, it should be noted that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing the embodiments of the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation, and therefore should not be understood as limiting the embodiments of the present invention. In addition, the terms "first", "second", and "third" are used for descriptive purposes only and should not be understood as indicating or implying relative importance.

[0034] In the description of the embodiments of the present invention, it should be noted that, unless otherwise specified or limited, the terms "connected" and "connection" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integral connections; mechanical connections, electrical connections; and direct connections or indirect connections through an intermediary. Those skilled in the art will understand the specific meanings of the above terms in the embodiments of the present invention based on the specific circumstances.

[0035] In the embodiments of the present invention, unless otherwise expressly specified or limited, a first feature being "above" or "below" a second feature may mean that the first and second features are in direct contact, or that the first and second features are in indirect contact through an intermediate medium. Furthermore, a first feature being "above," "above," or "above" a second feature may mean that the first feature is directly above or diagonally above the second feature, or simply means that the first feature is at a higher level than the second feature. A first feature being "below," "below," or "below" a second feature may mean that the first feature is directly below or diagonally below the second feature, or simply means that the first feature is at a lower level than the second feature.

[0036] In the description of this specification, the reference terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" mean that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the embodiment of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification and features of different embodiments or examples without contradiction.

[0037] Please refer to Figures 1 to 3The molten salt purification device according to the first embodiment of the present invention includes a heating furnace 1, a reactor 2, a sleeve 3, an air inlet and outlet device and a crucible 4. The heating furnace 1 is provided with multiple heating zones 7 in the height direction. Each adjacent two heating zones 7 are separated by an insulation layer 8, and each heating zone 7 can be individually temperature-controlled; part of the reactor 2 is arranged in the heating furnace 1 and extends into the multiple heating zones 7. The reactor 2 is provided with a reaction chamber 21 and a cavity port connected to the reaction chamber 21; the sleeve 3 is placed in the reaction chamber 21 from the cavity port and covers the cavity port. A placement chamber 31 is provided in the sleeve 3, and the air inlet and outlet device is connected to the placement chamber 31 for providing inert gas to the placement chamber 31; the crucible 4 is placed in the placement chamber 31, and the crucible 4 is used to accommodate the molten salt to be purified.

[0038] According to the molten salt purification device of the embodiment of the present invention, the molten salt to be purified is placed in the crucible 4, and the crucible 4 is placed in the placement cavity 31 of the sleeve 3. The sleeve 3 provides reaction environment conditions. At the same time, the sleeve 3 facilitates the removal and placement of the crucible 4 in the reaction cavity 21 of the reactor 2. The reactor 2 is installed in the heating furnace 1, and the sleeve 3 is used to seal the cavity opening of the reaction cavity 21 to prevent the volatilization of the molten salt. The heating furnace 1 is provided with multiple heating zones 7 arranged in sequence along the height direction. Each heating zone 7 can be individually temperature-controlled. The heating furnace 1 can heat and melt the molten salt to be purified in the crucible 4. After heating and melting the molten salt to be purified, each heating zone 7 can be controlled to slowly cool down from top to bottom so that the molten salt solidifies from top to bottom, completing the purification. The impurities will flow to the bottom of the crucible 4, thereby obtaining the upper layer of purified molten salt. The structure is simple.

[0039] Optionally, heating furnace 1 is an electric furnace to facilitate heating temperature control. Furnace 1 can be composed of multiple electric furnaces to form multiple heating zones 7. Alternatively, a single electric furnace can be divided into multiple heating components to independently control the heating temperature of each heating zone 7. The heating element of furnace 1 can be located at reactor 2 to heat the molten salt to be purified in crucible 4 through sleeve 3.

[0040] The inert gas introduced is argon or nitrogen to avoid corrosion of the furnace by air at high temperature.

[0041] In one embodiment, a thermal insulation layer is provided within the heating furnace 1, enclosing multiple heating zones 7 to prevent heat leakage. Furthermore, an insulation layer is provided between each adjacent heating zone 7, that is, between the upper and lower heating zones 7, to prevent the temperatures of the two heating zones 7 from interfering with each other. For example, while controlling the temperature of the upper heating zone 7 to cool, the lower heating zone 7 maintains a higher temperature. At this time, the temperature of the upper heating zone 7, due to the presence of the insulation layer, reduces the impact of the lower heating zone 7 on the temperature, thus preventing the temperature from being difficult to lower.

[0042] In one embodiment, the sleeve 3 is a stainless steel sleeve, which facilitates heat conduction and is relatively low in cost. Since the crucible 4 needs to be placed entirely within the reaction chamber 21, the crucible 4 is placed through the sleeve 3, and a portion of the sleeve 3 can be located outside the reaction chamber 21, making it easy to remove the sleeve 3, thereby facilitating the removal and placement of the crucible 4, or the molten salt. Optionally, the opposite side walls of the sleeve 3 are hollow structures to facilitate heat transfer to the crucible 4. In other words, the bottom of the sleeve 3 supports the crucible 4, and the side walls of the sleeve 3 form two parallel support walls that can stop the crucible 4 to prevent it from tipping over.

[0043] like Figure 1 As shown, according to one embodiment of the present invention, the crucible 4 extends in the height direction to cover and extend to each section of the heating zone 7. It will be understood that the crucible 4 in the figure is only an example and does not limit its actual size. Exemplarily, the crucible 4 extends along the placement cavity 31 to ensure that each section of the heating zone 7 is placed with molten salt to be purified, thereby improving the purification efficiency. After the molten salt to be purified located in the upper layer of the crucible 4 solidifies, since the heating zone 7 still maintains a certain heating temperature, the remaining impurities do not solidify and flow to the lower layer of the crucible 4, and the purified molten salt remains in the upper layer of the crucible 4. The multiple heating zones 7 lower the heating temperature in sequence from top to bottom, thereby gradually completing the purification of the molten salt to be purified in the crucible 4.

[0044] According to one embodiment of the present invention, the heating range of each heating zone 7 is 400°C to 700°C, that is, the heating temperature of each heating zone 7 can be controlled to vary within the range of 400°C to 700°C.

[0045] According to one embodiment of the present invention, each heating zone 7 is provided with a corresponding temperature sensor, and the temperature sensor is located at the middle position in the height direction of the heating zone 7. It is understood that the temperature sensor is a temperature measuring thermocouple, and each temperature measuring thermocouple is located at the middle position of each heating zone 7, which detects the temperature change of the heating zone 7 in real time during the reaction to facilitate temperature control.

[0046] like Figure 2 As shown, according to one embodiment of the present invention, the molten salt purification device includes a water cooling device 6, which is arranged around the top of the reactor 2 and is equipped with cooling water. In this embodiment, the water cooling device 6 is located outside the heating furnace 1 and is arranged around the top of the reactor 2 to cool the top of the reactor 2 and reduce the risk of burns caused by contact. It can be understood that the water cooling device 6 is provided with a water inlet 61 and a water outlet 62 to connect to an external water source, thereby providing circulating cooling water and improving the cooling effect.

[0047] Please refer to Figure 2 and Figure 3According to one embodiment of the present invention, the gas inlet and outlet device includes an inlet pipe 51, an outlet pipe 52, and a vacuum pipe 53 connected to the sleeve 3. The inlet pipe 51, the outlet pipe 52, and the vacuum pipe 53 are all connected to the placement chamber 31. It can be understood that the inlet pipe 51 is used to introduce an inert gas into the placement chamber 31. The inert gas can be argon. To provide a good reaction environment, the placement chamber 31 can be evacuated through the vacuum pipe 53 and then introduced with inert gas. The outlet pipe 52 can be used to discharge the gas after purification is completed.

[0048] According to one embodiment of the present invention, an end cap 32 is provided around the outer wall of the sleeve 3, which seals the cavity opening. Optionally, the end cap 32 is provided around the outer wall of the sleeve 3 and is integrally formed with the sleeve 3. When the sleeve 3 is inserted into the reaction chamber 21, the end cap 32 can seal the cavity opening of the reaction chamber 21 to reduce heat loss.

[0049] According to one embodiment of the present invention, the end cap 32 is provided with a threaded hole, through which the end cap 32 is connected to the reactor 2. It is understood that the end cap 32 is connected to the top of the reactor 2 by a threaded hole to prevent loosening and ensure the closed environment of the reaction chamber 21.

[0050] In one embodiment, a uniformly mixed LiCl-SrCl2 (5 wt%)-CsCl (5 wt%) molten salt is first prepared. After uniform mixing, the mixture is placed in a corundum crucible 4 and placed in an oven, heated to 150°C, and dried. For example, the heating furnace 1 is provided with a first heating zone 7, a second heating zone 7, a third heating zone 7, and a fourth heating zone 7, sequentially arranged from top to bottom.

[0051] After the mixed dried LiCl-SrCl2 (5wt%)-CsCl (5wt%) molten salt is placed in the crucible 4 in the stainless steel sleeve 3, the sleeve 3 is placed in the reactor 2, and the sleeve 3 and the reactor 2 are tightly connected with screws. The water cooling is turned on, and an inert gas is introduced into the placement chamber 31 as a protective gas. The multi-stage heating zone 7 is heated to 630°C by the heating furnace 1 and maintained at this temperature for more than 12 hours to completely melt the LiCl-SrCl2 (5wt%)-CsCl (5wt%) molten salt and mix uniformly. Then, the controller starts the program cooling and condensation of the first heating zone 7, slowly cooling in the temperature range of 630°C-590°C at a cooling rate of 5°C / h. After cooling to below 590°C, the heating of the first heating zone 7 is turned off. During this operation, the bottom heating zone 7 maintains the original heating temperature of 630°C. After the first heating zone 7 is turned off, the programmed cooling and condensation of the second heating zone 7 is started. The temperature is also slowly cooled in the temperature range of 630℃-590℃, with a cooling rate of 5℃ / h. After the temperature drops below 590℃, the heating of the second heating zone 7 is turned off. During this operation, the remaining heating zone 7 at the bottom maintains the original heating temperature. The remaining heating zones 7 are cooled from top to bottom in the same way until the molten salt is completely cooled. After that, the condensed molten salt is taken out, and the more transparent salt phase at the top of the salt column is the purified LiCl molten salt. The upper 75% LiCl molten salt after purification is lower than that before purification, in which Sr 2+ 、Cs + The removal rate of Sr can reach about 90%, and the removal rate of Sr can be further increased by secondary condensation. 2+ 、Cs + The removal rate is over 99%.

[0052] The molten salt purification method according to the second embodiment of the present invention includes:

[0053] Heating the heating furnace 1 until the molten salt mixture in the crucible 4 is melted;

[0054] The multi-stage heating zone 7 is cooled down stage by stage from top to bottom so that the molten salt in the crucible 4 solidifies stage by stage.

[0055] It is understandable that before heating the molten salt mixture, it is necessary to turn on the water cooling device 6 and introduce protective gas into the placement cavity 31 of the sleeve 3. It should be noted that the step-by-step cooling here means that when the first section is slowly cooled, the second section maintains the original heating temperature to prevent the molten salt to be purified in the second section from condensing before the molten salt to be purified in the first section.

[0056] According to one embodiment of the present invention, the step of gradually cooling the multi-stage heating zone 7 from top to bottom includes:

[0057] The heating temperature of the multiple heating zones 7 is gradually reduced to cool the heating zones 7. When the temperature of the heating zones 7 is lower than the melting point of the molten salt, the heating of the heating zones 7 is stopped, and the heating temperature of the next heating zones 7 is then reduced. It is understood that after solidification, the molten salt located in the upper section can be supported by the inner wall of the sleeve 3, or the density is lower in the upper section.

[0058] According to the above-mentioned molten salt purification method, the impurity metal ions in most molten salts can be purified, including but not limited to: Sr and Cs in LiCl-CsCl-SrCl2, LiCl-KCl-CsCl-SrCl2, LiF-KF-CsF-SrF2 molten salts, and lanthanides in LiCl-LaCl3, LiCl-KCl-LaCl3, LiF-KF-NaF-LaF3 molten salts.

[0059] The molten salt purification method according to an embodiment of the present invention includes the above-mentioned molten salt purification device, and therefore has all the technical effects of the above-mentioned molten salt purification device, which will not be repeated here.

[0060] Finally, it should be noted that the above embodiments are intended to illustrate the present invention only and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the embodiments, it should be understood by those skilled in the art that various combinations, modifications, or equivalent substitutions of the technical solutions of the present invention do not depart from the spirit and scope of the technical solutions of the present invention and are intended to be encompassed by the claims of the present invention.

Claims

1. A molten salt purification device, characterized in that: include: A heating furnace, wherein the heating furnace is provided with multiple heating zones in the height direction, each adjacent heating zone is separated by a heat insulation layer, and each heating zone can be individually temperature-controlled; A reactor, wherein a portion of the reactor is disposed in the heating furnace and extends into the multi-stage heating zone, the reactor being provided with a reaction chamber and a cavity opening communicating with the reaction chamber; The sleeve is placed in the reaction chamber from the cavity opening and covers the cavity opening. The sleeve is provided with a placement cavity. an air inlet and outlet device, the air inlet and outlet device being connected to the placement cavity and being used to provide inert gas to the placement cavity; A crucible is placed in the placement cavity, and is used to contain molten salt to be purified. The crucible extends in a height direction to cover and extend to each section of the heating zone.

2. The molten salt purification device according to claim 1, characterized in that The heating range of each heating zone is 400°C to 700°C.

3. The molten salt purification device according to claim 1, characterized in that Each heating zone is correspondingly provided with a temperature sensor, and the temperature sensor is located in the middle position of the heating zone in the height direction.

4. The molten salt purification device according to any one of claims 1 to 3, characterized in that: The molten salt purification device includes a water cooling device, which is arranged around the top of the reactor and is equipped with cooling water.

5. The molten salt purification device according to any one of claims 1 to 3, characterized in that: The air inlet and outlet device includes an air inlet pipe, an air outlet pipe and a vacuum pipe connected to the sleeve, and the air inlet pipe, the air outlet pipe and the vacuum pipe are all connected to the placement cavity.

6. The molten salt purification device according to any one of claims 1 to 3, characterized in that: An end cover is provided on the outer wall of the sleeve, and the end cover is sealed on the cavity opening.

7. The molten salt purification device according to claim 6, characterized in that: The end cover is provided with a threaded hole, and the end cover is connected to the reactor through the threaded hole.

8. A molten salt purification method, characterized in that: The molten salt purification method is implemented using the molten salt purification device according to any one of claims 1 to 7, and the steps include: heating the heating furnace until the molten salt mixture in the crucible is melted; The multi-stage heating zones are cooled section by section from top to bottom so that the molten salt in the crucible solidifies section by section.

9. The molten salt purification method according to claim 8, characterized in that: The step of gradually cooling the multi-stage heating zones from top to bottom comprises: The heating temperature of multiple heating zones is gradually reduced to cool the heating zones. When the temperature of a heating zone is lower than the melting point of the molten salt, heating of the heating zone is stopped and the heating temperature of the next heating zone is then reduced.

Images