Molten salt purification device and molten salt purification method

Abstract

The invention relates to the technical field of fused salt purification, and provides a fused salt purification device and a fused salt purification method.The fused salt purification device comprises a heating furnace, heat insulation layers, a reactor, a sleeve, a gas inlet and outlet device and a crucible, the heating furnace is provided with multiple sections of heating areas in the height direction, and the heating areas are separated by the heat insulation layers and can independently control the temperature; the reactor is partially arranged in the heating furnace and extends into the multiple sections of heating areas, and the reactor is provided with a reaction cavity and a cavity opening communicated with the reaction cavity; the sleeve is placed in the reaction cavity from the cavity opening and covers the cavity opening, a placement cavity is formed in the sleeve, and the gas inlet and outlet device is communicated with the placement cavity and used for providing inert gas for the placement cavity; the crucible is placed in the containing cavity and used for containing the fused salt to be purified. After the to-be-purified fused salt is heated and melted, each section of heating area can be controlled from top to bottom to slowly cool, so that the fused salt is solidified from top to bottom, purification is completed, impurities flow to the bottom of the crucible, the upper-layer purified fused salt is obtained, and 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] The dry reprocessing technology based on molten salt electrolysis is considered to be the most promising dry reprocessing technology for spent fuel. In the molten salt electrolysis dry reprocessing process, the difference in redox potential between actinides such as uranium (U) and plutonium (Pu) and fragmentation elements in the molten salt system is utilized to separate and recover actinides through potential control. During the separation and recovery process, lanthanides and active fragmentation elements such as Cs and Sr will continue to accumulate in the molten salt, changing the physical and chemical properties of the molten salt system and generating a large amount of waste salt. Considering the environmental and economic benefits, the purification and reuse of waste salt is very important. In order to achieve the purification and reuse of molten salt and minimize radioactive waste, it is necessary to purify the lanthanides and active fragmentation elements such as Cs and Sr in the waste molten salt. The local condensation method has been proven to be an effective molten salt purification method for separating Cs and Sr from waste salt. However, most local condensation devices use a method in which a mechanical arm drives a crucible or a heating zone or a condensation plate to move, which results in a relatively complex and cumbersome procedure, high difficulty in operation, and high economic cost. In addition, the local condensation device requires strict control of the precise temperature of the condensation plate, so it needs to couple many thermocouples and sensors, and the structure is complex. 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 the purification of molten salt.

[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 comprises: A heating furnace, wherein the heating furnace is provided with multiple heating zones in the height direction, each two adjacent heating zones are 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 zones, and the reactor is provided with a reaction chamber and a cavity opening communicating with the reaction chamber; A sleeve is placed in the reaction chamber from the cavity opening and covers the cavity opening, and a placement cavity is provided in the sleeve.

[0006] An air inlet and outlet device, the air inlet and outlet device is connected to the placement cavity and is 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.

[0007] 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 conveniently 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, and 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 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, and the purification is completed. The impurities will flow to the bottom of the crucible, thereby obtaining the molten salt after the upper layer is purified, and the structure is simple.

[0008] According to an embodiment of the present invention, the crucible extends in the height direction to cover and extend to each section of the heating zone.

[0009] According to an embodiment of the present invention, the heating range of each heating zone is 400°C to 700°C.

[0010] According to an embodiment of the present invention, each section of the 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.

[0011] 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.

[0012] 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.

[0013] According to one embodiment of the present invention, an end cover is provided around the outer wall of the sleeve, and the end cover seals the cavity opening.

[0014] 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.

[0015] The molten salt purification method according to the second aspect of the present invention includes: heating the heating furnace until the molten salt mixture in the crucible is melted; The multi-stage heating zones are cooled down stage by stage from top to bottom so that the molten salt in the crucible solidifies stage by stage.

[0016] According to one embodiment of the present invention, the step of cooling the multiple heating zones step by step from top to bottom comprises: The heating temperatures of the multiple heating zones are 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.

[0017] 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.

[0018] Additional aspects and advantages of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or related technologies, the drawings required for use in the embodiments or related technical descriptions are briefly introduced below. 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 creative work.

[0020] Figure 1 is a schematic structural diagram of a molten salt purification device provided in an embodiment of the present invention; 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; Figure 3 is a schematic top view of a partial structure of a molten salt purification device provided in an embodiment of the present invention; Reference numerals: 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

[0021] The following embodiments of the present invention are described in further detail in conjunction with 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.

[0022] 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" and the like indicate positions or positional relationships based on the positions or positional relationships 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 devices or elements referred to must have a specific orientation, be constructed and operate in a specific orientation, and therefore cannot be understood as limitations on the embodiments of the present invention. In addition, the terms "first", "second", and "third" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance.

[0023] In the description of the embodiments of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "connected" and "connection" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium. For ordinary technicians in this field, the specific meanings of the above terms in the embodiments of the present invention can be understood according to specific circumstances.

[0024] In the embodiments of the present invention, unless otherwise clearly specified and limited, the first feature being "above" or "below" the second feature may mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, the first feature being "above", "above" and "above" the second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. The first feature being "below", "below" and "below" the second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0025] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means 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 may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0026] 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 a plurality of heating zones 7 in the height direction. Each two adjacent 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 plurality of heating zones 7. The reactor 2 is provided with a reaction chamber 21 and a cavity opening connected to the reaction chamber 21; the sleeve 3 is placed in the reaction chamber 21 from the cavity opening and covers the cavity opening. A placement chamber 31 is provided in the sleeve 3. The air inlet and outlet device is connected to the placement chamber 31 to provide an 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.

[0027] 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, and the reaction environment conditions are provided by the sleeve 3. At the same time, the crucible 4 is conveniently placed in the reaction cavity 21 of the reactor 2 through the sleeve 3. The reactor 2 is installed in the heating furnace 1, and the sleeve 3 is sealed at the cavity opening of the reaction cavity 21 to prevent the volatilization of the molten salt. The heating furnace 1 is provided with a plurality of heating zones 7 arranged in sequence along the height direction, and 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, and the purification is completed. The impurities will flow to the bottom of the crucible 4, thereby obtaining the molten salt after the upper layer is purified, and the structure is simple.

[0028] Optionally, the heating furnace 1 is an electric heating furnace, which is convenient for controlling the heating temperature. The heating furnace 1 can be composed of a plurality of electric heating furnaces to form a multi-section heating zone 7. Of course, one electric heating furnace can also be divided into a plurality of heating components to achieve separate control of the heating temperature of each section of the heating zone 7. The heating element of the heating furnace 1 can be arranged at the reactor 2 to heat the molten salt to be purified in the melting crucible 4 through the sleeve 3.

[0029] The inert gas introduced is argon or nitrogen to avoid corrosion of the furnace by air at high temperature.

[0030] In one embodiment, a heat-insulating layer is provided in the heating furnace 1, and the heat-insulating layer covers the multiple heating zones 7 to prevent heat leakage. In addition, a heat-insulating layer is provided between each two adjacent heating zones 7, that is, a heat-insulating layer is provided between the upper and lower heating zones 7 to prevent the temperatures of the two heating zones 7 from affecting each other. For example, when the temperature of the upper heating zone 7 is controlled to be lowered, the temperature of the lower heating zone 7 is maintained at a higher heating temperature. At this time, the temperature of the upper heating zone 7 is reduced due to the presence of the heat-insulating layer, thereby reducing the influence of the heating temperature of the lower heating zone 7, so as to avoid the situation where the temperature is difficult to lower.

[0031] In one embodiment, the sleeve 3 is a stainless steel sleeve, which is convenient for heat conduction and has low cost. Since the crucible 4 needs to be placed in the reaction chamber 21 as a whole, the crucible 4 is placed through the sleeve 3, and part of the sleeve 3 can be located outside the reaction chamber 21, which is convenient for taking the sleeve 3, thereby facilitating the taking and placing of the crucible 4, or the taking and placing of the molten salt. Optionally, the opposite side walls of the sleeve 3 are hollow structures to facilitate heat transfer to the crucible 4, that is, the bottom of the sleeve 3 supports the crucible 4, and the side walls of the sleeve 3 form two parallel support walls, which can stop the crucible 4 to prevent it from tipping over.

[0032] 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. When 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 thus 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 from top to bottom in sequence, thereby gradually completing the purification of the molten salt to be purified in the crucible 4.

[0033] According to an embodiment of the present invention, the heating range of each heating zone 7 is 400°C~700°C, that is, the heating temperature of each heating zone 7 can be controlled to vary within the range of 400°C~700°C.

[0034] 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 in the middle of the height direction of the heating zone 7. It can be understood that the temperature sensor is a temperature measuring thermocouple, and each temperature measuring thermocouple is located in the middle of each heating zone 7, which detects the temperature change of the heating zone 7 during the reaction in real time, so as to control the temperature.

[0035] 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 cooling water is installed in the water cooling device 6. 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.

[0036] Please refer to Figure 2 and Figure 3According to one embodiment of the present invention, the air inlet and outlet device includes an air inlet pipe 51, an air outlet pipe 52 and a vacuum pipe 53 connected to the sleeve 3, and the air inlet pipe 51, the air outlet pipe 52 and the vacuum pipe 53 are all connected to the placement chamber 31. It can be understood that the air inlet pipe 51 is used to introduce an inert gas into the placement chamber 31, and the inert gas can be argon. In order to provide a good reaction environment, the placement chamber 31 can be vacuumed through the vacuum pipe 53, and then the inert gas can be introduced. The air outlet pipe 52 can be used to discharge the gas after purification is completed.

[0037] According to one embodiment of the present invention, an end cap 32 is provided around the outer wall of the sleeve 3, and the end cap 32 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.

[0038] According to one embodiment of the present invention, the end cap 32 is provided with a threaded hole, and the end cap 32 is connected to the reactor 2 through the threaded hole. It can be understood that the end cap 32 is connected to the top of the reactor 2 by a thread to prevent loosening, thereby ensuring the closed environment of the reaction chamber 21.

[0039] In one embodiment, first, a uniformly mixed LiCl-SrCl 2 (5wt%)-CsCl (5wt%) molten salt. After being mixed evenly, it is placed in a corundum crucible 4, placed in an oven and heated to 150°C to dry the moisture. Exemplarily, 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 from top to bottom.

[0040] The mixed and dried LiCl-SrCl 2 After the (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 make LiCl-SrCl 2The (5wt%)-CsCl(5wt%) molten salt is completely melted and mixed evenly, and then the controller is used to start the program cooling and condensation of the first heating zone 7, slowly cooling in the temperature range of 630℃-590℃, and the cooling rate is 5℃ / h. After cooling to below 590℃, the heating of the first heating zone 7 is turned off. During this operation, the heating zone 7 at the bottom maintains the original heating temperature of 630℃. After the first heating zone 7 is turned off, the program cooling and condensation of the second heating zone 7 is started, and the temperature is also slowly cooled in the temperature range of 630℃-590℃, and the cooling rate is 5℃ / h. After cooling to 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. According to the same method, the remaining heating zones 7 are cooled from top to bottom in sequence 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 higher than that before purification, among 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%.

[0041] The molten salt purification method according to the second aspect of the present invention includes: Heating the heating furnace 1 until the molten salt mixture in the crucible 4 is melted; 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.

[0042] It is understandable that before heating the molten salt mixture, the water cooling device 6 needs to be turned on and protective gas needs to be introduced 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 avoid the molten salt to be purified in the second section condensing before the molten salt to be purified in the first section.

[0043] According to one embodiment of the present invention, the step of cooling the multi-stage heating zone 7 from top to bottom step by step includes: 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 zone 7 is reduced. It can be understood that the molten salt located in the upper section after solidification can be supported on the inner wall of the sleeve 3, or the density is lower and located in the upper section.

[0044] According to the above molten salt purification method, most of the impure metal ions in the molten salt can be purified, including but not limited to: LiCl-CsCl-SrCl 2 , LiCl-KCl-CsCl-SrCl 2, LiF-KF-CsF-SrF 2 Sr and Cs in molten salts, and LiCl-LaCl 3 , LiCl-KCl-LaCl 3 , LiF-KF-NaF-LaF 3 Lanthanides in molten salts.

[0045] 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.

[0046] Finally, it should be noted that the above embodiments are only used to illustrate the present invention, rather than to limit the present invention. Although the present invention is 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 should be included in the scope of 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 two adjacent heating zones are 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 zones, and the reactor is provided with a reaction chamber and a cavity opening communicating with the reaction chamber; A sleeve is placed in the reaction chamber from the cavity opening and covers the cavity opening, and a placement cavity is provided in the sleeve. An air inlet and outlet device, the air inlet and outlet device is connected to the placement cavity and is 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.

2. The molten salt purification device according to claim 1, characterized in that: The crucible extends in a height direction to cover and extend to each section of the heating zone.

3. 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.

4. 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.

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

6. The molten salt purification device according to any one of claims 1 to 4, characterized in that: The air inlet and outlet device comprises 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.

7. The molten salt purification device according to any one of claims 1 to 4, characterized in that: An end cover is arranged around the outer wall of the sleeve, and the end cover seals the cavity opening.

8. The molten salt purification device according to claim 7, 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.

9. A molten salt purification method, characterized in that: The molten salt purification method is implemented by using the molten salt purification device according to any one of claims 1 to 8, 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 down stage by stage from top to bottom so that the molten salt in the crucible solidifies stage by stage.

10. The molten salt purification method according to claim 9, characterized in that: The step of gradually cooling the multiple heating zones from top to bottom comprises: The heating temperatures of the multiple heating zones are 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.

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