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CN-121976255-A - Electrolytic tank and method for preparing high-purity sodium metal

CN121976255ACN 121976255 ACN121976255 ACN 121976255ACN-121976255-A

Abstract

The invention relates to the technical field of sodium metallurgy, and discloses an electrolytic cell and a method for preparing high-purity sodium metal, wherein the electrolytic cell comprises a cell body, a crucible, an anode rod, a cathode plate and a porous ceramic diaphragm; the accommodating space of the crucible is divided into an anode chamber in the middle area and a cathode chamber at the periphery of the anode chamber by a porous ceramic diaphragm, an anode rod is vertically arranged in the tank body and extends downwards into the anode chamber, two cathode sheets are respectively arranged at two sides of the anode rod and extend downwards into the cathode chamber, the crucible is provided with a sodium collecting structure, and the porous ceramic diaphragm has a gradient pore diameter structure. According to the invention, through the porous ceramic diaphragm with the gradient pore diameter, the selective migration of sodium ions and the high-efficiency blocking of impurity ions are realized, and the impurity content is obviously reduced from an electrolysis source by combining with an optimized electrode material. Meanwhile, by utilizing the special sodium collecting and guiding structure of the crucible, the in-situ, continuous collection and closed export of liquid sodium are realized, and high-purity metal sodium can be directly obtained.

Inventors

  • XIAO CHUNHUI
  • Shao Kehan
  • LIN PEILING

Assignees

  • 西安交通大学

Dates

Publication Date
20260505
Application Date
20260203

Claims (10)

  1. 1. The high-purity sodium molten salt electrolytic tank with the in-situ separation function is characterized by comprising a tank body, a crucible (5), an anode rod (1), a cathode sheet (3) and a porous ceramic diaphragm (12), wherein the crucible (5) is arranged at the bottom of the tank body, a containing space of the crucible is divided into an anode chamber positioned in a middle area and a cathode chamber positioned at the periphery of the anode chamber by the porous ceramic diaphragm (12), the anode rod (1) is vertically arranged in the tank body and extends downwards into the anode chamber, and two cathode sheets (3) are respectively arranged at two sides of the anode rod (1) and extend downwards into the cathode chamber; the porous ceramic diaphragm (12) has a gradient pore diameter structure, wherein the average pore diameter of the side close to the anode rod (1) is larger than that of the side close to the cathode sheet (3); The crucible (5) is provided with a conical funnel-shaped crucible body (5-1) serving as a sodium collecting area, an annular diversion trench (5-2) is arranged at the upper edge of the funnel, and the cone angle of the funnel part of the crucible body (5-1) is 135-155 degrees.
  2. 2. The high-purity sodium molten salt electrolysis cell with an in-situ separation function according to claim 1, wherein the annular diversion trench (5-2) is connected with an outlet pipeline (5-3).
  3. 3. The high purity sodium molten salt electrolysis cell with in-situ separation function according to claim 1, wherein the porous ceramic membrane (12) has an average pore size of 1-2 μm and a thickness of 2-3mm.
  4. 4. The high-purity sodium molten salt electrolytic tank with in-situ separation function according to claim 1, wherein the anode rod (1) is high-density graphite subjected to dipping treatment, the density is greater than 1.8 g/cm 3 , and the cathode sheet (3) is low-carbon steel with a nickel layer of 5-10 μm on the surface.
  5. 5. The high-purity sodium molten salt electrolysis cell with the in-situ separation function according to claim 1, wherein two cathode sheets (3) are symmetrically distributed on two sides of the anode rod (1), and the interval between the anode rod (1) and the cathode sheets (3) is 3-4 cm.
  6. 6. The high-purity sodium molten salt electrolysis cell with the in-situ separation function according to claim 1, wherein the cell body sequentially comprises a shell, a heat preservation layer, an electrolysis cell inner layer (7) and an inner steel sleeve (8) from outside to inside, and electric heating wires (9) and heat insulation materials (10) are arranged on the side wall and the bottom of the cell body.
  7. 7. The high-purity sodium molten salt electrolytic tank with in-situ separation function according to any one of claims 1 to 6, further comprising a tank cover (13), wherein the tank cover (13) is arranged at the top end of the tank body, the upper end of the anode rod (1) penetrates out of the tank cover (13), a gas collecting hood (4) is connected to a through hole in the tank cover (13) for the anode rod (1) to penetrate out, and the gas collecting hood (4) is sleeved on the anode rod (1).
  8. 8. A method for preparing high purity sodium by using the high purity sodium molten salt electrolyzer with in situ separation function as claimed in any one of claims 1 to 7, characterized by comprising the following steps: s1, loading sodium-containing chloride molten salt into the high-purity sodium molten salt electrolysis tank, and heating to 505-600 ℃ under the protection of inert atmosphere; S2, applying current density of 80-120 mA/cm < 2 > for electrolysis; S3, floating up and collecting liquid sodium generated by electrolysis in a sodium collecting structure of the crucible (5), and guiding the liquid sodium out to an external collecting device through the tangential outlet pipeline.
  9. 9. The method for preparing high-purity sodium according to claim 8, wherein the sodium-containing chloride molten salt is a NaCl-CaCl 2 molten salt.
  10. 10. The method for preparing high purity sodium according to claim 8, wherein in step S3, electrolytically generated chlorine is collected and led out through the gas hood (4).

Description

Electrolytic tank and method for preparing high-purity sodium metal Technical Field The invention relates to the technical field of sodium metallurgy, in particular to an electrolytic cell and a method for preparing high-purity metallic sodium. Background Sodium metal is an important basic raw material and is widely applied to the fields of nuclear industry, sodium ion batteries, fine chemical engineering, aerospace and the like. At present, sodium metal is produced by a fused salt electrolysis method such as NaCl-CaCl 2 and the like in industry. However, the existing electrolysis process and device have a plurality of bottlenecks that firstly, the purity of an electrolysis product is low, impurity ions such as calcium, barium and the like are easy to co-deposit with sodium, so that the impurity content in sodium is high, and is difficult to meet the high-end application requirements, secondly, the subsequent purification process is complex, a plurality of working procedures such as filtration, vacuum distillation and the like are generally needed, the energy consumption is high, the metal yield loss is large, furthermore, the service life of key parts of the electrolysis tank is short, a graphite anode is easy to permeate and corrode by chlorine, a low-carbon steel cathode is easy to alloy with sodium, so that the equipment maintenance is frequent and the cost is high, finally, hidden danger exists in operation safety, secondary reaction of sodium and chlorine is likely to occur, and the high-temperature molten salt operation environment is bad. Therefore, developing a molten salt electrolytic tank capable of realizing in-situ separation of high-purity sodium from an electrolysis source, simplifying a purification process, and improving material durability and operation safety has become a technical problem to be solved in the art. Disclosure of Invention In view of the above, the invention aims to provide a high-purity sodium fused salt electrolytic tank with an in-situ separation function and a method for preparing high-purity sodium, so as to solve the problems of low product purity, complex purification process, serious material corrosion, poor safety and the like in the prior art. In order to achieve the aim, the invention provides a high-purity sodium molten salt electrolytic tank with an in-situ separation function, which comprises a tank body, a crucible, an anode rod, cathode plates and a porous ceramic diaphragm, wherein the crucible is arranged at the bottom of the tank body, a containing space of the crucible is divided into an anode chamber positioned in a middle area and a cathode chamber positioned at the periphery of the anode chamber by the porous ceramic diaphragm; The porous ceramic diaphragm has a gradient pore diameter structure, wherein the average pore diameter of one side close to the anode rod is larger than that of one side close to the cathode plate, and the structure allows sodium ions to selectively pass through and effectively blocks larger impurity ions such as calcium, barium and the like, so that the purity of a product is improved from the source; the crucible is provided with a crucible body which is used as a sodium collecting area and is in a conical funnel shape, and the upper edge of the funnel is provided with an annular diversion trench. Specifically, the funnel-shaped crucible body comprises a funnel part and a cylinder part which are arranged in an up-down communication way, and the cone angle of the funnel part is 135-155 degrees. As a further preferable technical scheme of the invention, the annular diversion trench is connected with an outlet pipeline. Still further preferably, the outlet conduit is directed tangentially from the side wall of the channel. As a further preferable technical scheme of the invention, the average pore diameter of the porous ceramic membrane is 1-2 mu m, and the thickness is 2-3mm. As a further preferable technical scheme of the invention, the anode rod is high-density graphite subjected to dipping treatment, the density is more than 1.8 g/cm 3 so as to delay chlorine permeation corrosion, and the cathode sheet is low-carbon steel with a nickel layer of 5-10 mu m on the surface so as to prevent sodium-iron alloying. As a further preferable technical scheme of the invention, the two cathode sheets are symmetrically distributed on two sides of the anode rod, the distance between the anode rod and the cathode sheets is 3-4cm, and the distance combines the effective isolation of the ceramic diaphragm and the lower ohmic pressure drop. As a further preferable technical scheme of the invention, the tank body sequentially comprises a shell, a heat preservation layer, an electrolytic tank inner layer 7 and an inner steel sleeve 8 from outside to inside, and the side wall and the bottom of the tank body are provided with heating wires and heat insulation materials. As a further preferable technical scheme of the invention, the high-purity sod