Electrochemical reduction of metal oxides

Abstract

A process for electrochemically reducing metal oxide feed material in a solid state is disclosed. The process includes the steps of agitating an electrolyte and metal oxide powders in the electrolyte and applying an electrical potential across a cathode in contact with the electrolyte and an anode and electrochemically reducing the metal oxides.

1 . A process for electrochemically reducing metal oxide feed material in a solid state comprising agitating an electrolyte and metal oxide powders in the electrolyte and applying an electrical potential across (a) a cathode in contact with the electrolyte and (b) an anode and electrochemically reducing the metal oxides.  
     
     
         2 . The process defined in  claim 1  includes agitating an electrolyte and metal oxide powders to an extent required to cause intermittent contact between the powder particles and the cathode that is sufficient to enable reduction of titania powders and restrict sintering of the powder particles together that could adversely affect the reduction of unreduced or partially reduced powders.  
     
     
         3 . The process defined in  claim 1  includes selecting the particle size of the powders so that the electrolyte and the powders form a slurry in which the powder particles are suspended in the electrolyte.  
     
     
         4 . The process defined in  claim 1  includes agitating the electrolyte and the metal oxide powders by physical means or by gas injection.  
     
     
         5 . The process defined in  claim 1  wherein the powders are sub-micron size.  
     
     
         6 . The process defined in  claim 1  wherein the electrolyte is a CaCl 2 -based electrolyte containing CaO.  
     
     
         7 . The process defined in  claim 6  includes applying a potential across the anode and the cathode that is above the decomposition potential of CaO and below the decomposition of CaCl 2 .  
     
     
         8 . The process defined in  claim 1  includes positioning a member in contact with the electrolyte so that reduced powders can deposit on the member.  
     
     
         9 . The process defined in  claim 8  includes removing the member from the electrolyte and stripping deposited reduced powders from the member.  
     
     
         10 . The process defined in  claim 1  wherein the process is a multi-stage process with electrolyte and partially reduced and unreduced powders in a slurry form being transferred from a first stage to one or more than one successive stage in the process and being reduced in each stage.  
     
     
         11 . The process defined in  claim 1  wherein the process is a continuous process that includes passing a slurry of the electrolyte and metal oxide powders through a reactor that defines a pathway for flow of the slurry between an inlet and an outlet and includes one or more than one anode and one or more than one cathode in the pathway.  
     
     
         12 . The process defined in  claim 11  includes agitating the slurry to cause the slurry to flow in a turbulent flow pattern along the pathway.  
     
     
         13 . The process defined in  claim 11  includes agitating the slurry by introducing the slurry in a turbulent flow into the reactor.  
     
     
         14 . The process defined in  claim 11 , when operated on a continuous basis, includes separating reduced powders from the electrolyte downstream of the outlet of the pathway and processing the reduced powders as required.  
     
     
         15 . The process defined in  claim 1  wherein the metal oxide particles are titanium oxide particles.  
     
     
         16 . An apparatus for electrochemically reducing metal oxide powders comprising: 
 (a) a means for containing a bath of a molten electrolyte and metal oxide particles in the electrolyte,    (b) a cathode in contact with the electrolyte,    (c) an anode,    (d) a means for applying a potential across the anode and the cathode, and    (e) a means for agitating the electrolyte.    
     
     
         17 . The apparatus defined in  claim 16  wherein the means for applying the potential across the anodes and the cathode includes (a) a power source and (b) an electrical circuit that electrically interconnects the power source, the anodes, and the cathode.