Molten salt electrolyte primary crystal temperature measuring device and method

Abstract

The invention discloses a molten salt electrolyte primary crystal temperature measuring device and method, and belongs to the technical field of molten salt electrolyte physical property testing, the device comprises a high temperature furnace, a crucible, a sealing cover, a support, a conductance cell, a thermocouple, a resistance measuring instrument, a temperature measuring instrument and a computer, and the conductance cell adopts a duplex integrated structure or a single-tube split structure. According to the molten salt electrolyte primary crystal temperature measuring device and method, the conductance cell is used for measuring the resistance of the molten salt electrolyte, the curve of the melt resistance changing along with the temperature is drawn, when non-conductive crystals are separated out from the electrode surface of the conductance cell, inflection points appear on the curve of the melt resistance changing along with the temperature, and the molten salt electrolyte primary crystal temperature is measured. The temperature corresponding to the inflection point is the primary crystal temperature of the molten salt electrolyte; and meanwhile, a thermocouple is used for synchronously measuring the melt temperature of the molten salt electrolyte, a melt step cooling curve is drawn, and through mutual verification of the melt step cooling curve and a curve of melt resistance changing along with the temperature, the identification reliability of the molten salt electrolyte primary crystal temperature is further improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of physical property testing of molten salt electrolytes, and particularly relates to a device and method for measuring the primary crystallization temperature of molten salt electrolytes. Background Technique

[0002] The primary crystallization temperature of a molten salt electrolyte refers to the temperature at which crystals first appear during the process of the molten salt changing from a completely molten state to a solid state by slow cooling. The primary crystallization temperature is an important basic physical property of the molten salt electrolyte. Because when studying the physical properties of the molten salt electrolyte, it is first necessary to understand the primary crystallization temperature of the molten salt, and then other physical properties of the molten salt can be studied on this basis. In industrial electrolysis production, the electrolysis temperature is determined based on the primary crystallization temperature of the molten salt. In addition, in the field of molten salt heat storage, the primary crystallization temperature of the molten salt directly affects the lower limit of the operation of the heat storage system. When the temperature is lower than this temperature, the molten salt will lose its fluidity. Therefore, it is very important to accurately measure the primary crystallization temperature of the molten salt electrolyte.

[0003] At present, the primary crystallization temperature of molten salt electrolytes can be measured by various methods, including the cooling curve method, differential thermal analysis method, etc. These measurement methods utilize the characteristic that heat is released during the crystallization of molten salt electrolytes. Taking the cooling curve method as an example, when measuring the primary crystallization temperature of a molten salt electrolyte, first, the molten salt electrolyte is completely melted, then a thermocouple with an exposed hot end is directly inserted into the melt, and then it is slowly cooled to gradually cool the melt. At the same time, a cooling curve is plotted. When crystals precipitate at the hot end of the thermocouple, the heat released during crystallization will cause an inflection point to appear on the cooling curve, and the temperature corresponding to the inflection point is the primary crystallization temperature of the molten salt electrolyte.

[0004] However, the cooling curve method is only applicable to simple molten salt systems because there are relatively clear inflection points on the cooling curves of simple molten salt systems, which are relatively easy to identify. However, with the in-depth research work, the composition of the molten salt electrolyte has become more and more complex, making it difficult to find clear inflection points on the cooling curves of complex molten salt systems. Therefore, the traditional cooling curve method can no longer meet the scientific research and industrial production needs of complex molten salt systems.

[0005] The Chinese patent application with the publication number CN116297673A discloses a method for detecting and analyzing the primary crystallization temperature of an electrolyte. This solution determines the primary crystallization temperature of the electrolyte by utilizing the difference in the variation of the conductivity of the electrolyte melt with temperature when the electrolyte melt is in a turbid state below the primary crystallization temperature and in a clear state above the primary crystallization temperature. However, the method used to measure the conductivity of the electrolyte melt in this solution belongs to the CVCC method, and the CVCC method is a discontinuous molten salt conductivity measurement method. When measuring each conductivity data, the electrodes need to be moved. This solution requires measuring the conductivity values at 11 temperature points and does not continuously plot the conductivity curve. Therefore, when using this solution to measure the primary crystallization temperature of the molten salt electrolyte, not only is the operation complex, but also the subsequent data analysis is rather cumbersome. Summary of the Invention

[0006] Aiming at the problems existing in the prior art, the present invention provides a device and method for measuring the primary crystallization temperature of a molten salt electrolyte. The resistance of the molten salt electrolyte is measured by using a conductance cell, and a curve of the melt resistance varying with temperature is plotted. When non-conductive crystals precipitate on the surface of the electrodes of the conductance cell, an inflection point will appear on the curve of the melt resistance varying with temperature, and the temperature corresponding to the inflection point is the primary crystallization temperature of the molten salt electrolyte. At the same time, the melt temperature of the molten salt electrolyte is synchronously measured by using a thermocouple, and a melt cooling curve is plotted. By mutually verifying the melt cooling curve and the curve of the melt resistance varying with temperature, the recognition reliability of the primary crystallization temperature of the molten salt electrolyte is further improved.

[0007] To achieve the above object, the present invention adopts the following technical solution: A device for measuring the primary crystallization temperature of a molten salt electrolyte includes a high-temperature furnace, a crucible, a cover, a bracket, a conductance cell, a thermocouple, a resistance measuring instrument, a temperature measuring instrument, and a computer. The crucible is placed inside the high-temperature furnace, and the crucible is used to hold the molten salt electrolyte. The cover is buckled on the open mouth of the crucible. The bracket is fixedly arranged above the high-temperature furnace. The conductance cell and the thermocouple are vertically installed on the bracket, and the lower ends of the conductance cell and the thermocouple pass through the cover and are inserted into the molten salt electrolyte. The upper end of the conductance cell is electrically connected to the resistance measuring instrument through a wire, and the resistance measuring instrument is electrically connected to the computer. The upper end of the thermocouple is electrically connected to the temperature measuring instrument through a wire, and the temperature measuring instrument is electrically connected to the computer.

[0008] The conductance cell adopts a double-connected integral structure or a single-tube split structure.

[0009] When the conductivity cell adopts a dual-connected integrated structure, it includes a first electrode rod, a second electrode rod, a double-through-hole electrode protection tube, and a double-through-hole capillary tube; the double-through-hole electrode protection tube is vertically fixed on the bracket, and the thermocouple is distributed in parallel with the double-through-hole electrode protection tube; the first electrode rod and the second electrode rod are respectively fixedly inserted into the two through-holes of the double-through-hole electrode protection tube, and the first electrode rod, the second electrode rod, and the double-through-hole electrode protection tube are an integrated prefabricated assembly. The tops of the first electrode rod and the second electrode rod are connected to a resistance measuring instrument through wires; the double-through-hole capillary tube is vertically fixedly inserted into the cover and the lower end of the tube body is inserted into the molten salt electrolyte. The double-through-hole capillary tube is located directly below the double-through-hole electrode protection tube and they are coaxially distributed; the first electrode rod and the second electrode rod respectively pass through the two through-holes of the double-through-hole capillary tube, and the lower ends of the rod bodies of the first electrode rod and the second electrode rod are both inserted into the molten salt electrolyte.

[0010] When the conductivity cell adopts a dual-connected integrated structure, the cover is respectively provided with a thermocouple through-hole and a double-through-hole capillary tube through-hole; the thermocouple is inserted and matched with the thermocouple through-hole; the double-through-hole electrode protection tube is fixedly inserted and matched with the double-through-hole capillary tube through-hole.

[0011] When the conductivity cell adopts a single-tube split structure, it includes a first electrode rod, a second electrode rod, a first single-through-hole electrode protection tube, a second single-through-hole electrode protection tube, a first single-through-hole capillary tube, and a second single-through-hole capillary tube; the first single-through-hole electrode protection tube and the second single-through-hole electrode protection tube are both vertically fixed on the bracket; the thermocouple is located between the first single-through-hole electrode protection tube and the second single-through-hole electrode protection tube; the first electrode rod is fixedly inserted into the first single-through-hole electrode protection tube, and the first electrode rod and the first single-through-hole electrode protection tube are an integrated prefabricated assembly. The top of the first electrode rod is connected to a resistance measuring instrument through a wire; the second electrode rod is fixedly inserted into the second single-through-hole electrode protection tube, and the second electrode rod and the second single-through-hole electrode protection tube are an integrated prefabricated assembly. The top of the second electrode rod is connected to a resistance measuring instrument through a wire; the first single-through-hole capillary tube and the second single-through-hole capillary tube are both vertically fixedly inserted into the cover, and the lower ends of the tube bodies of the first single-through-hole capillary tube and the second single-through-hole capillary tube are both inserted into the molten salt electrolyte; the first single-through-hole capillary tube is located directly below the first single-through-hole electrode protection tube and they are coaxially distributed; the second single-through-hole capillary tube is located directly below the second single-through-hole electrode protection tube and they are coaxially distributed; the first electrode rod passes through the first single-through-hole capillary tube, and the lower end of the rod body of the first electrode rod is inserted into the molten salt electrolyte; the second electrode rod passes through the second single-through-hole capillary tube, and the lower end of the rod body of the second electrode rod is inserted into the molten salt electrolyte.

[0012] When the conductivity cell adopts a single-tube split structure, the cover is respectively provided with a thermocouple perforation, a first single-hole electrode protection tube perforation and a second single-hole electrode protection tube perforation; the thermocouple is fitted through the thermocouple perforation; the first single-hole capillary tube is fixedly fitted through the first single-hole electrode protection tube perforation; and the second single-hole capillary tube is fixedly fitted through the second single-hole electrode protection tube perforation.

[0013] A method for measuring the primary crystallization temperature of molten salt electrolyte uses the molten salt electrolyte primary crystallization temperature measuring device as described above, and includes the following steps:

[0014] Step 1: Load the powdered molten salt electrolyte into the crucible, and then send the crucible containing the molten salt electrolyte into the high-temperature furnace. The high-temperature furnace heats the crucible until the molten salt electrolyte is completely melted.

[0015] Step 2: After the molten salt electrolyte is completely melted, fasten the cover to the open mouth of the crucible.

[0016] Step 3: Install the conductivity cell and the thermocouple between the cover and the bracket respectively, and then lower the height of the bracket until the thermocouple, the first electrode rod and the second electrode rod are all inserted into the melted molten salt electrolyte.

[0017] Step 4: Connect the first electrode rod and the second electrode rod to the resistance measuring instrument through wires, connect the thermocouple to the temperature measuring instrument through wires, and then connect the resistance measuring instrument and the temperature measuring instrument to the computer.

[0018] Step 5: Lower the heating temperature of the high-temperature furnace to synchronously lower the temperature of the molten salt electrolyte in the crucible.

[0019] Step 6: Synchronously draw the curve of the melt resistance of the molten salt electrolyte changing with temperature and the melt cooling curve in the computer.

[0020] In Step 3, when the conductivity cell adopts a double-tube integrated structure, the installation process of the conductivity cell is as follows: First, fixedly install the double-through-hole capillary tube through the double-through-hole capillary tube perforation on the cover. The installed double-through-hole capillary tube is directly inserted into the melted molten salt electrolyte. Then, install the thermocouple and the double-through-hole electrode protection tube on the bracket. The installed thermocouple is directly above the thermocouple perforation, and the installed double-through-hole capillary tube perforation and the first electrode rod and the second electrode rod thereon are directly above the double-through-hole capillary tube.

[0021] In Step 3, when the conductivity cell adopts a single-tube split structure, the installation process of the conductivity cell is as follows: First, the first single-hole capillary and the second single-hole capillary are respectively fixed and inserted through the first single-hole electrode protection tube perforation and the second single-hole electrode protection tube perforation into the cover. After installation, the first single-hole capillary and the second single-hole capillary are directly inserted into the molten salt electrolyte. Then, the thermocouple, the first single-hole electrode protection tube, and the second single-hole electrode protection tube are installed on the bracket. After installation, the thermocouple is located directly above the thermocouple perforation. After installation, the first single-hole electrode protection tube and the first electrode rod thereon are located directly above the first single-hole capillary. After installation, the second single-hole electrode protection tube and the second electrode rod thereon are located directly above the second single-hole capillary.

[0022] Advantages of the present invention:

[0023] For the molten salt electrolyte primary crystallization temperature measuring device and method of the present invention, the conductivity cell is used to measure the resistance of the molten salt electrolyte, and a curve of the melt resistance changing with temperature is plotted. When non-conductive crystals precipitate on the surface of the electrodes of the conductivity cell, an inflection point will appear on the curve of the melt resistance changing with temperature, and the temperature corresponding to the inflection point is the primary crystallization temperature of the molten salt electrolyte. At the same time, the thermocouple is used to synchronously measure the melt temperature of the molten salt electrolyte, and a melt cooling curve is plotted. By mutually verifying the melt cooling curve and the curve of the melt resistance changing with temperature, the recognition reliability of the primary crystallization temperature of the molten salt electrolyte is further improved. Description of the Drawings

[0024] Figure 1 It is a schematic structural diagram of a molten salt electrolyte primary crystallization temperature measuring device (the conductivity cell adopts a double-tube integrated structure) of the present invention;

[0025] Figure 2 It is a schematic structural diagram of a molten salt electrolyte primary crystallization temperature measuring device (the conductivity cell adopts a single-tube split structure) of the present invention;

[0026] Figure 3 [[ID=,20]]It is a schematic structural diagram of the combination of the cover, the bracket, the conductivity cell (adopting a double-tube integrated structure), and the thermocouple of the present invention;

[0027] Figure 4 It is a schematic structural diagram of the combination of the cover, the bracket, the conductivity cell (adopting a single-tube split structure), and the thermocouple of the present invention;

[0028] Figure 5 [[ID=,28]]It is a graph of the change of the melt resistance with temperature when NaCl is used as the molten salt electrolyte;

[0029] Figure 6 It is a melt cooling curve graph when NaCl is used as the molten salt electrolyte;

[0030] Figure 7It is a graph showing the variation of the melt resistance of MgCl2-KCl-NaCl-AlF3 as a molten salt electrolyte with temperature;

[0031] Figure 8 It is a cooling curve graph of the melt of MgCl2-KCl-NaCl-AlF3 as a molten salt electrolyte;

[0032] In the figure, 1 - high-temperature furnace, 2 - crucible, 3 - cover, 4 - bracket, 5 - conductance cell, 6 - thermocouple, 7 - resistance measuring instrument, 8 - temperature measuring instrument, 9 - computer, 10 - first electrode rod, 11 - second electrode rod, 12 - double-through-hole electrode protection tube, 13 - double-through-hole capillary tube, 14 - first single-through-hole electrode protection tube, 15 - second single-through-hole electrode protection tube, 16 - first single-through-hole capillary tube, 17 - second single-through-hole capillary tube, 18 - thermocouple perforation, 19 - double-through-hole capillary tube perforation, 20 - first single-through-hole electrode protection tube perforation, 21 - second single-through-hole electrode protection tube perforation, 22 - molten salt electrolyte. Specific embodiments

[0033] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0034] As Figures 1 to 4 shown, a device for measuring the primary crystallization temperature of a molten salt electrolyte includes a high-temperature furnace 1, a crucible 2, a cover 3, a bracket 4, a conductance cell 5, a thermocouple 6, a resistance measuring instrument 7, a temperature measuring instrument 8 and a computer 9; the crucible 2 is placed in the high-temperature furnace 1, and the crucible 2 is used to hold the molten salt electrolyte 22; the cover 3 is buckled on the open mouth of the crucible 2; the bracket 4 is fixedly arranged above the high-temperature furnace 1; the conductance cell 5 and the thermocouple 6 are vertically installed on the bracket 4, and the lower ends of the conductance cell 5 and the thermocouple 6 pass through the cover 3 and are inserted into the molten salt electrolyte 22; the upper end of the conductance cell 5 is electrically connected to the resistance measuring instrument 7 through a wire, and the resistance measuring instrument 7 is electrically connected to the computer 9; the upper end of the thermocouple 6 is electrically connected to the temperature measuring instrument 8 through a wire, and the temperature measuring instrument 8 is electrically connected to the computer 9.

[0035] Specifically, the high-temperature furnace 1 is a well-type furnace with an open top, the crucible 2 is a cylindrical graphite crucible, the cover 3 is a disc-shaped graphite cover, the thermocouple 6 is an S-type thermocouple, the temperature measurement deviation of the thermocouple 6 is 1.8 °C, the resistance measuring instrument 7 is a digital bridge of model TH2830, and the temperature measuring instrument 8 is a temperature controller of model AI719.

[0036] The conductance cell 5 adopts a double-connected integrated structure or a single-tube split structure.

[0037] When the conductivity cell 5 adopts a double-connected integrated structure, it includes a first electrode rod 10, a second electrode rod 11, a double-through-hole electrode protection tube 12 and a double-through-hole capillary tube 13; the double-through-hole electrode protection tube 12 is vertically and fixedly installed on the bracket 4, and the thermocouple 6 is distributed in parallel with the double-through-hole electrode protection tube 12; the first electrode rod 10 and the second electrode rod 11 are respectively fixedly inserted into the two through-holes of the double-through-hole electrode protection tube 12. The first electrode rod 10, the second electrode rod 11 and the double-through-hole electrode protection tube 12 are an integrated prefabricated assembly. The tops of the first electrode rod 10 and the second electrode rod 11 are connected to the resistance measuring instrument 7 through wires; the double-through-hole capillary tube 13 is vertically fixedly inserted into the cover 3 and the lower end of the tube body is inserted into the molten salt electrolyte 22. The double-through-hole capillary tube 13 is located directly below the double-through-hole electrode protection tube 12 and the two are coaxially distributed; the first electrode rod 10 and the second electrode rod 11 respectively pass through the two through-holes of the double-through-hole capillary tube 13, and the lower ends of the rod bodies of the first electrode rod 10 and the second electrode rod 11 are both inserted into the molten salt electrolyte 22.

[0038] Specifically, the first electrode rod 10 and the second electrode rod 11 are made of platinum wire, the double-through-hole electrode protection tube 12 is made of corundum tube, and the double-through-hole capillary tube 13 is made of hot-pressed or pyrolytic boron nitride ceramic tube.

[0039] When the conductivity cell 5 adopts a double-connected integrated structure, the cover 3 is respectively provided with a thermocouple through-hole 18 and a double-through-hole capillary tube through-hole 19; the thermocouple 6 is inserted and matched with the thermocouple through-hole 18; the double-through-hole electrode protection tube 12 is fixedly inserted and matched with the double-through-hole capillary tube through-hole 19.

[0040] When the conductance cell 5 adopts a single-tube split structure, it includes a first electrode rod 10, a second electrode rod 11, a first single-hole electrode protection tube 14, a second single-hole electrode protection tube 15, a first single-hole capillary 16 and a second single-hole capillary 17; the first single-hole electrode protection tube 14 and the second single-hole electrode protection tube 15 are both vertically fixed on the bracket 4; the thermocouple 6 is located between the first single-hole electrode protection tube 14 and the second single-hole electrode protection tube 15; the first electrode rod 10 is fixedly inserted into the first single-hole electrode protection tube 14, and the first electrode rod 10 and the first single-hole electrode protection tube 14 are an integrated prefabricated assembly, and the top end of the first electrode rod 10 is connected to the resistance measuring instrument 7 through a wire; the second electrode rod 11 is fixedly inserted into the second single-hole electrode protection tube 15, and the second electrode rod 11 and the second single-hole electrode protection tube 15 are an integrated prefabricated assembly, and the top end of the second electrode rod 11 is connected to the resistance measuring instrument 7 through a wire; the first single-hole capillary 16 and the second single-hole capillary 17 are both vertically fixedly inserted into the cover 3, and the lower ends of the tube bodies of the first single-hole capillary 16 and the second single-hole capillary 17 are both inserted into the molten salt electrolyte 22; the first single-hole capillary 16 is located directly below the first single-hole electrode protection tube 14 and they are coaxially distributed; the second single-hole capillary 17 is located directly below the second single-hole electrode protection tube 15 and they are coaxially distributed; the first electrode rod 10 passes through the first single-hole capillary 16, and the lower end of the rod body of the first electrode rod 10 is inserted into the molten salt electrolyte 22; the second electrode rod 11 passes through the second single-hole capillary 17, and the lower end of the rod body of the second electrode rod 11 is inserted into the molten salt electrolyte 22.

[0041] When the conductance cell 5 adopts a single-tube split structure, the cover 3 is respectively provided with a thermocouple perforation 18, a first single-hole electrode protection tube perforation 20 and a second single-hole electrode protection tube perforation 21; the thermocouple 6 is fitted with the thermocouple perforation 18; the first single-hole capillary 16 is fixedly fitted with the first single-hole electrode protection tube perforation 20; the second single-hole capillary 17 is fixedly fitted with the second single-hole electrode protection tube perforation 21.

[0042] Specifically, the first electrode rod 10 and the second electrode rod 11 are made of platinum wire, the first single-hole electrode protection tube 14 and the second single-hole electrode protection tube 15 are made of corundum tubes, and the first single-hole capillary 16 and the second single-hole capillary 17 are made of hot-pressed or pyrolytic boron nitride ceramic tubes.

[0043] A method for measuring the primary crystallization temperature of a molten salt electrolyte adopts the molten salt electrolyte primary crystallization temperature measuring device, and includes the following steps:

[0044] Step 1: Load the powdery molten salt electrolyte 22 into the crucible 2, and then send the crucible 2 containing the molten salt electrolyte 22 into the high-temperature furnace 1, and heat the crucible 2 by the high-temperature furnace 1 until the molten salt electrolyte 22 is completely melted;

[0045] Step 2: After the molten salt electrolyte 22 is completely melted, snap the cover 3 onto the open end of the crucible 2.

[0046] Step 3: Install the conductivity cell 5 and the thermocouple 6 between the cover 3 and the bracket 4 respectively. Then lower the height of the bracket 4 until the thermocouple 6, the first electrode rod 10, and the second electrode rod 11 are all inserted into the molten molten salt electrolyte 22.

[0047] Step 4: Connect the first electrode rod 10 and the second electrode rod 11 to the resistance measuring instrument 7 through wires, connect the thermocouple 6 to the temperature measuring instrument 8 through wires, and then connect the resistance measuring instrument 7 and the temperature measuring instrument 8 to the computer 9.

[0048] Step 5: Lower the heating temperature of the high-temperature furnace 1 to synchronously decrease the temperature of the molten salt electrolyte 22 in the crucible 2.

[0049] Step 6: Synchronously plot the curve of the melt resistance of the molten salt electrolyte 22 changing with temperature and the melt cooling curve in the computer 9.

[0050] In Step 3, when the conductivity cell 5 adopts a double-connected integrated structure, the installation process of the conductivity cell 5 is as follows: First, fix and pass the double-through-hole capillary 13 through the double-through-hole capillary perforation 19 onto the cover 3. After installation, the double-through-hole capillary 13 is directly inserted into the molten molten salt electrolyte 22. Then, install the thermocouple 6 and the double-through-hole electrode protection tube 12 on the bracket 4. After installation, the thermocouple 6 is directly above the thermocouple perforation 18. After installation, the double-through-hole capillary perforation 19 and the first electrode rod 10 and the second electrode rod 11 thereon are directly above the double-through-hole capillary 13.

[0051] In Step 3, when the conductivity cell 5 adopts a single-tube split structure, the installation process of the conductivity cell 5 is as follows: First, fix and pass the first single-hole capillary 16 and the second single-hole capillary 17 through the first single-hole electrode protection tube perforation 20 and the second single-hole electrode protection tube perforation 21 onto the cover 3 respectively. After installation, the first single-hole capillary 16 and the second single-hole capillary 17 are directly inserted into the molten molten salt electrolyte 22. Then, install the thermocouple 6, the first single-hole electrode protection tube 14, and the second single-hole electrode protection tube 15 on the bracket 4. After installation, the thermocouple 6 is directly above the thermocouple perforation 18. After installation, the first single-hole electrode protection tube 14 and the first electrode rod 10 thereon are directly above the first single-hole capillary 16. After installation, the second single-hole electrode protection tube 15 and the second electrode rod 11 thereon are directly above the second single-hole capillary 17.

[0052] When the molten salt electrolyte 22 is NaCl, the curve of the melt resistance changing with temperature is as Figure 5 shown, and the melt cooling curve is as Figure 6As shown. From Figure 5 it can be seen that the inflection point temperature of the curve is 802.6 °C. Since the temperature measurement deviation of the thermocouple 6 is 1.8 °C, the measured primary crystallization temperature of NaCl should be 800.8 °C. Compared with the standard value of the primary crystallization temperature of NaCl at 800.7 °C, the measurement error is 0.02%. From Figure 6 it can be seen that the inflection point temperature of the curve is 802.8 °C. Since the temperature measurement deviation of the thermocouple 6 is 1.8 °C, the measured primary crystallization temperature of NaCl should be 801 °C. Compared with the standard value of the primary crystallization temperature of NaCl at 800.7 °C, the measurement error is 0.04%. By measuring the primary crystallization temperature of NaCl, the effectiveness of the present invention is fully verified.

[0053] When the molten salt electrolyte 22 is MgCl2-KCl-NaCl-AlF3, the curve of the melt resistance changing with temperature is as Figure 7 shown, and the cooling curve of the melt is as Figure 8 shown. From Figure 7 it can be seen that the inflection point temperature of the curve is 458 °C. Since the temperature measurement deviation of the thermocouple 6 is 1.8 °C, the measured primary crystallization temperature of MgCl2-KCl-NaCl-AlF3 should be 456.2 °C. From Figure 8 it can be seen that the inflection point temperature of the curve is 457.7 °C. Since the temperature measurement deviation of the thermocouple 6 is 1.8 °C, the measured primary crystallization temperature of MgCl2-KCl-NaCl-AlF3 should be 455.9 °C. Therefore, through the cooling curve of the melt and the curve of the melt resistance changing with temperature, mutual verification is achieved, effectively improving the reliability of identifying the primary crystallization temperature of the molten salt electrolyte.

[0054] The solutions in the embodiments are not intended to limit the protection scope of the present invention. Any equivalent implementation or modification without departing from the present invention is included in the protection scope of the present invention.

Claims

1. A molten salt electrolyte primary crystallization temperature measuring device, characterized in that: It includes a high-temperature furnace, a crucible, a cover, a bracket, a conductivity cell, a thermocouple, a resistance measuring instrument, a temperature measuring instrument and a computer; the crucible is placed inside the high-temperature furnace, and the crucible is used to hold molten salt electrolyte; the cover is buckled on the open mouth of the crucible; the bracket is fixedly arranged above the high-temperature furnace; the conductivity cell and the thermocouple are vertically installed on the bracket, and the lower ends of the conductivity cell and the thermocouple pass through the cover and are inserted into the molten salt electrolyte; the upper end of the conductivity cell is electrically connected to the resistance measuring instrument through a wire, and the resistance measuring instrument is electrically connected to the computer; the upper end of the thermocouple is electrically connected to the temperature measuring instrument through a wire, and the temperature measuring instrument is electrically connected to the computer.

2. The primary crystallization temperature measuring device for molten salt electrolyte according to claim 1, characterized in that: The conductivity cell adopts a double-connected integral structure or a single-tube split structure.

3. The primary crystallization temperature measuring device for molten salt electrolyte according to claim 2, wherein: When the conductivity cell adopts a double-connected integral structure, it includes a first electrode rod, a second electrode rod, a double-through-hole electrode protection tube and a double-through-hole capillary tube; the double-through-hole electrode protection tube is vertically fixedly installed on the bracket, and the thermocouple is distributed side by side with the double-through-hole electrode protection tube; the first electrode rod and the second electrode rod are respectively fixedly inserted into the two through-holes of the double-through-hole electrode protection tube, and the first electrode rod, the second electrode rod and the double-through-hole electrode protection tube are an integral prefabricated assembly, and the tops of the first electrode rod and the second electrode rod are connected to the resistance measuring instrument through wires; the double-through-hole capillary tube is vertically fixedly inserted into the cover and the lower end of the tube body is inserted into the molten salt electrolyte, and the double-through-hole capillary tube is located directly below the double-through-hole electrode protection tube and they are coaxially distributed; the first electrode rod and the second electrode rod respectively pass through the two through-holes of the double-through-hole capillary tube, and the lower ends of the rod bodies of the first electrode rod and the second electrode rod are inserted into the molten salt electrolyte.

4. A molten salt electrolyte primary crystallization temperature measuring device according to claim 3, characterized in that: When the conductivity cell adopts a double-connected integral structure, the cover is respectively provided with a thermocouple through-hole and a double-through-hole capillary tube through-hole; the thermocouple is inserted and matched with the thermocouple through-hole; the double-through-hole electrode protection tube is fixedly inserted and matched with the double-through-hole capillary tube through-hole.

5. The primary crystallization temperature measuring device for molten salt electrolyte according to claim 2, characterized in that: When the conductivity cell adopts a single-tube split structure, it includes a first electrode rod, a second electrode rod, a first single-hole electrode protection tube, a second single-hole electrode protection tube, a first single-hole capillary tube and a second single-hole capillary tube; the first single-hole electrode protection tube and the second single-hole electrode protection tube are both vertically fixed on the bracket; the thermocouple is located between the first single-hole electrode protection tube and the second single-hole electrode protection tube; the first electrode rod is fixedly inserted into the first single-hole electrode protection tube, and the first electrode rod and the first single-hole electrode protection tube are an integrated prefabricated assembly, and the top end of the first electrode rod is connected to the resistance measuring instrument through a wire; the second electrode rod is fixedly inserted into the second single-hole electrode protection tube, and the second electrode rod and the second single-hole electrode protection tube are an integrated prefabricated assembly, and the top end of the second electrode rod is connected to the resistance measuring instrument through a wire; the first single-hole capillary tube and the second single-hole capillary tube are both vertically fixedly inserted into the cover, and the lower ends of the tube bodies of the first single-hole capillary tube and the second single-hole capillary tube are both inserted into the molten salt electrolyte; the first single-hole capillary tube is located directly below the first single-hole electrode protection tube and they are coaxially distributed; the second single-hole capillary tube is located directly below the second single-hole electrode protection tube and they are coaxially distributed; the first electrode rod passes through the first single-hole capillary tube, and the lower end of the rod body of the first electrode rod is inserted into the molten salt electrolyte; the second electrode rod passes through the second single-hole capillary tube, and the lower end of the rod body of the second electrode rod is inserted into the molten salt electrolyte.

6. The primary crystallization temperature measuring device for molten salt electrolyte according to claim 5, characterized in that: When the conductivity cell adopts a single-tube split structure, the cover is respectively provided with a thermocouple perforation, a first single-hole electrode protection tube perforation and a second single-hole electrode protection tube perforation; the thermocouple is inserted and matched with the thermocouple perforation; the first single-hole capillary tube is fixedly inserted and matched with the first single-hole electrode protection tube perforation; the second single-hole capillary tube is fixedly inserted and matched with the second single-hole electrode protection tube perforation.

7. A method for measuring the primary crystallization temperature of a molten salt electrolyte, which uses the molten salt electrolyte primary crystallization temperature measuring device described in claim 1, is characterized in that, It includes the following steps: Step 1: Load the powdery molten salt electrolyte into the crucible, and then send the crucible containing the molten salt electrolyte into the high-temperature furnace, and the high-temperature furnace heats the crucible until the molten salt electrolyte is completely melted. Step 2: When the molten salt electrolyte is completely melted, buckle the cover onto the open mouth of the crucible. Step 3: Install the conductivity cell and the thermocouple between the cover and the bracket respectively, and then lower the height of the bracket until the thermocouple, the first electrode rod and the second electrode rod are all inserted into the molten salt electrolyte. Step 4: Connect the first electrode rod and the second electrode rod to the resistance measuring instrument through wires, connect the thermocouple to the temperature measuring instrument through wires, and then connect the resistance measuring instrument and the temperature measuring instrument to the computer. Step 5: Lower the heating temperature of the high-temperature furnace to synchronously lower the temperature of the molten salt electrolyte in the crucible. Step 6: Synchronously draw the curve of the melt resistance of the molten salt electrolyte changing with temperature and the melt cooling curve in the computer.

8. A molten salt electrolyte primary crystallization temperature measuring device according to claim 7, characterized in that: In Step 3, when the conductivity cell adopts a double - tube integrated structure, the installation process of the conductivity cell is as follows: First, pass the double - through - hole capillary through the double - through - hole capillary perforation and fix it on the cover. The installed double - through - hole capillary is directly inserted into the molten salt electrolyte. Then, install the thermocouple and the double - through - hole electrode protection tube on the bracket. The installed thermocouple is directly above the thermocouple perforation. The installed double - through - hole capillary perforation, the first electrode rod and the second electrode rod on it are directly above the double - through - hole capillary.

9. The primary crystallization temperature measuring device for molten salt electrolyte according to claim 7, characterized in that: In Step 3, when the conductivity cell adopts a single - tube split - type structure, the installation process of the conductivity cell is as follows: First, pass the first single - hole capillary and the second single - hole capillary through the first single - hole electrode protection tube perforation and the second single - hole electrode protection tube perforation respectively and fix them on the cover. The installed first single - hole capillary and the second single - hole capillary are directly inserted into the molten salt electrolyte. Then, install the thermocouple, the first single - hole electrode protection tube and the second single - hole electrode protection tube on the bracket. The installed thermocouple is directly above the thermocouple perforation. The installed first single - hole electrode protection tube and the first electrode rod on it are directly above the first single - hole capillary. The installed second single - hole electrode protection tube and the second electrode rod on it are directly above the second single - hole capillary.

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