Low resistance electrode assemblies for production of metals

Abstract

An electrode assembly for use in a reduction cell for the production of metal such as aluminum. The electrode comprises an electrically conductive carbon electrode block with an electrically conductive metal member connected thereto. At least one solid, conductive metal insert is at least partly received in the carbon electrode block with an interference fit, such that the insert exerts a lateral force on the carbon electrode block. The insert provides an improved electrically conductive connection between the carbon electrode block and the conductive metal member, with reduced resistance. The insert may provide a direct connection between the electrode block and the metal member, or the connection may be provided through a layer of cast iron or other metal element provided between the electrode block and the metal member. The electrode assembly may either comprise an anode or a cathode.

1 . An electrode assembly for use in a reduction cell for the production of metal, the electrode assembly comprising:
 (a) an electrically conductive carbon electrode block having a first surface and a second surface, wherein the first surface faces an interior of the reduction cell when the electrode assembly is in use;   (b) an electrically conductive metal member having a first end and a second end, wherein the first end of the metal member is connected to the carbon electrode block in an electrically conductive manner, and the second end of the metal member is adapted for connection to a buss bar in an electrically conductive manner;   (c) a solid, conductive metal insert at least partly received in the carbon electrode block, wherein the insert extends into the carbon electrode block from the second surface thereof; and   
       wherein the metal insert is received in the carbon electrode block with an interference fit, such that the insert exerts a lateral force on the carbon electrode block. 
     
     
         2 . The electrode assembly of  claim 1 , wherein:
 the electrode is a pre-baked carbon anode,   the first surface of the carbon electrode block is a bottom surface thereof,   the electrically conductive metal member comprises a vertical conductor rod,   the electrically conductive metal member further comprises a vertical stub at its first end, and   the carbon electrode block has a top surface opposite the bottom surface, a recess is formed in the top surface, with an end of the vertical stub being received in the recess.   
     
     
         3 . (canceled) 
     
     
         4 . The electrode assembly of  claim 2 , wherein the second surface in which the insert extends comprises an inner surface of the recess, the inner surface being selected from a bottom surface and a side surface of the recess. 
     
     
         5 . The electrode assembly of  claim 4 , wherein the insert extends into the bottom surface of the recess and extends vertically downwardly therefrom; or
 wherein the insert extends into the side surface of the recess and extends radially outwardly therefrom; and/or   wherein the insert is inclined downwardly and outwardly from said second surface.   
     
     
         6 - 7 . (canceled) 
     
     
         8 . The electrode assembly of  claim 4 , comprising a plurality of said inserts provided in the bottom surface and/or the side surface of the recess, with each of said inserts being at least partly received in the carbon electrode block; and
 wherein a portion of each of said inserts protrudes from the bottom surface or the side surface of the recess.   
     
     
         9 - 10 . (canceled) 
     
     
         11 . The electrode assembly of  claim 4 , wherein the recess is provided with a conductive metal lining through which an electrically conductive connection is formed between the stub and the carbon electrode block, and wherein the insert or the plurality of inserts is in direct, electrically conductive contact with the conductive metal lining of the recess. 
     
     
         12 . The electrode assembly of  claim 11 , wherein at least a portion of the conductive metal lining comprises a cast portion which is formed in situ between the stub and the carbon electrode block. 
     
     
         13 . The electrode assembly of  claim 12 , wherein a portion of the conductive metal lining comprises a solid preform which is combined with the cast portion during formation of the metal lining, and wherein the insert or the plurality of inserts is in direct, electrically conductive contact with the preform prior to formation of the cast portion. 
     
     
         14 - 24 . (canceled) 
     
     
         25 . The electrode assembly of  claim 1 , wherein the electrode is a pre-baked carbon cathode, wherein the first surface of the carbon electrode block is a top surface thereof and the carbon electrode block has a bottom surface opposite the top surface, and wherein the electrically conductive metal member comprises a current collector bar having a first portion received in a slot in the bottom surface, the current collector bar and the bottom surface being substantially parallel. 
     
     
         26 . The electrode assembly of  claim 25 , wherein a layer of cast iron or carbon paste is provided in the slot, between the current collector bar and the carbon electrode block; and
 wherein the second surface in which the insert extends comprises an inner surface of the slot, the inner surface of the slot being selected from a top surface and a side surface of the slot.   
     
     
         27 . (canceled) 
     
     
         28 . The electrode assembly of  claim 26 , wherein the insert is partly received in the inner surface of the slot, and has a head which is embedded in the layer of cast iron or carbon paste. 
     
     
         29 . The electrode assembly of  claim 28 , wherein the head of the insert is flat, the electrode assembly further comprising a conductive metal liner and/or a conductive metal washer received between the flat head of the insert and the carbon electrode block. 
     
     
         30 - 41 . (canceled) 
     
     
         42 . The electrode assembly of  claim 1 , wherein a thickness of the insert and the width of the bore are sized relative to one another such that an interface contact pressure between the insert and the adjoining carbon electrode block is at least about 1 kPa. 
     
     
         43 - 45 . (canceled) 
     
     
         46 . The electrode assembly of  claim 1 , wherein the second end of the metal member, which is adapted for connection to the buss bar, includes a connecting surface which is adapted to mate with the buss bar, and wherein the connecting surface is electroplated or clad with corrosion resistant conductive material. 
     
     
         47 . (canceled) 
     
     
         48 . The electrode assembly of  claim 1 , wherein the electrode is pre-baked and the insert is inserted into the carbon electrode block either before or after the electrode is pre-baked. 
     
     
         49 - 50 . (canceled) 
     
     
         51 . The electrode assembly of  claim 25 , wherein the current collector bar comprises a core and an outer casing surrounding the core. 
     
     
         52 . The electrode assembly of  claim 51 , wherein the core is comprised of a first metal with a lower electrical resistance than steel, and wherein the casing is comprised of a second metal having a melting point higher than the highest operating temperature of the reduction cell. 
     
     
         53 . The electrode assembly of  claim 52 , wherein the core comprises copper or an alloy thereof. 
     
     
         54 . The electrode assembly of  claim 52 , wherein the casing comprises steel, nickel or alloys such as stainless steel. 
     
     
         55 . The electrode assembly of  claim 51 , wherein the casing comprises a sealed enclosure which surrounds the core on all sides within the potshell. 
     
     
         56 . The electrode assembly of  claim 55 , wherein the casing comprises a pre-formed shell and the core is formed by casting of the first metal into the casing. 
     
     
         57 . (canceled) 
     
     
         58 . The electrode assembly of  claim 25 , wherein the current collector bar has a second portion extending outwardly of said slot, wherein the second portion of the collector bar comprises an end portion having a smaller cross-sectional area than the first portion of the collector bar which is received inside the slot. 
     
     
         59 - 61 . (canceled) 
     
     
         62 . The electrode assembly of  claim 26 , wherein the slot has a top surface and a pair of side surfaces, and wherein the layer of cast iron or carbon paste is provided only between the side surfaces of the slot and opposing side surfaces of the current collector bar; and
 wherein a space between the top surface of slot and an opposing top surface of the current collector bar is filled with an electrically and thermally insulating refractory material.   
     
     
         63 . (canceled) 
     
     
         64 . The electrode assembly of  claim 62 , wherein the top edge of the cast iron layer between each of the side surfaces of the slot and the opposing side surface of the current collector bar varies in height along the length of the slot; and
 wherein the cast iron layer has a top edge which is spaced from the top surface of the slot by a distance which varies along the length of the slot.   
     
     
         65 - 66 . (canceled) 
     
     
         67 . The electrode assembly of  claim 64 , wherein said thermally insulating refractory material fills any spaces between the top edge of the cast iron layer and the top surface of the slot. 
     
     
         68 - 75 . (canceled)