Molten salt electrolyzer for reducing metal, method for electrolyzing the same, and process for producing refractory metal with use of reducing metal

Abstract

A molten salt electrolyzer for reducing metal comprises an electrolytic cell filled with a molten salt composed of a reducing metal chloride, an anode immersed in the molten salt of the electrolytic cell and surrounded by a first wall at the periphery thereof, and a cathode immersed in the molten salt of the electrolytic cell and surrounded by a second wall at the periphery thereof.

1 . A molten salt electrolyzer for reducing metal, comprising:
 an electrolytic cell filled with a molten salt composed of a reducing metal chloride;   an anode and a cathode immersed in the molten salt of the electrolytic cell;   a first wall surrounding the periphery of the anode; and   a second wall surrounding the periphery of the cathode,   wherein the first wall extends to the bottom of the electrolytic cell and comprises a porous body.   
   
   
       2 . The molten salt electrolyzer for reducing metal according to  claim 1 , wherein the first wall and the second wall have an opening through which the molten salt can communicate each other. 
   
   
       3 . (canceled) 
   
   
       4 . The molten salt electrolyzer for reducing metal according to  claim 1 , wherein the anode is made of graphite. 
   
   
       5 . The molten salt electrolyzer for reducing metal according to  claim 1 , wherein the cathode is made of one of two materials among a carbon steel and a stainless steel. 
   
   
       6 . The molten salt electrolyzer for reducing metal according to  claim 1 , wherein the first wall is made of one of a metal oxide, a metal nitride, and a metal carbide. 
   
   
       7 . The molten salt electrolyzer for reducing metal according to  claim 1 , wherein the second wall is made of one of a metal, a metal nitride, and a metal carbide. 
   
   
       8 . The molten salt electrolyzer for reducing metal according to  claim 6 , wherein the metal oxide comprises at least one selected from the group consisting of alumina, silica, zirconia, and magnesia. 
   
   
       9 . The molten salt electrolyzer for reducing metal according to  claim 6 , wherein the metal nitride is selected from the group consisting of silicon nitride, boron nitride, titanium nitride, zirconium nitride, and tantalum nitride. 
   
   
       10 . The molten salt electrolyzer for reducing metal according  claim 6 , wherein the metal carbide is selected from the group consisting of silicon carbide, boron carbide, titanium carbide, zirconium carbide, and tantalum carbide. 
   
   
       11 . The molten salt electrolyzer for reducing metal according to  claim 7 , wherein the metal is selected from the group consisting of titanium, niobium, tantalum, and stainless steel. 
   
   
       12 . The molten salt electrolyzer for reducing metal according to  claim 1 , wherein the reducing metal is calcium. 
   
   
       13 . The molten salt electrolyzer for reducing metal according to  claim 1 , wherein the molten salt is selected from the group consisting of calcium chloride, a mixed salt of calcium chloride and potassium chloride, and a mixed salt of calcium chloride and calcium fluoride. 
   
   
       14 . A process for producing a reducing metal by molten salt electrolysis using the molten salt electrolyzer for reducing metal according to  claim 1 . 
   
   
       15 . The process for producing a reducing metal by molten salt electrolysis according to  claim 14 , wherein a temperature of the molten salt is maintained in a temperature region that is higher than the melting point thereof by 5 to 50° C. 
   
   
       16 . The process for producing a reducing metal by molten salt electrolysis according to  claim 14 , wherein the reducing metal is calcium. 
   
   
       17 . A process for producing a refractory metal by reducing the refractory metal chlorides, which is selected from the group consisting of titanium, zirconium, tantalum, and niobium, with the reducing metal produced by the process according to  claim 14 . 
   
   
       18 . The molten salt electrolyzer for reducing metal according to  claim 7 , wherein the metal nitride is selected from the group consisting of silicon nitride, boron nitride, titanium nitride, zirconium nitride, and tantalum nitride. 
   
   
       19 . The molten salt electrolyzer for reducing metal according to  claim 7 , wherein the metal carbide is selected from the group consisting of silicon carbide, boron carbide, titanium carbide, zirconium carbide, and tantalum carbide.