Cathode current collector/connector for a Hall-Heroult cell
An electrolytic cell for the production of aluminium including collector bars under the cathode, namely a copper collector bar whose external terminal end is connected by a conductor element providing electrical connection of the collector bar to an external bus. This conductor element comprises a flexible connector strip of the same or a different highly conductive metal as the conductor bar, such as copper.
1. A cathode current collector and connector assembly assembled in a carbon cathode of a Hall-Heroult cell for the production of aluminium, said assembly comprising:
at least one collector bar of a copper or copper alloy that is located under the carbon cathode is in direct electrical contact with the carbon cathode, wherein the or each collector bar comprises one or two terminal end part or parts extending outwardly up to inside or outside a cell outer cover to a connector, whereat said terminal end part(s) of the or each collector bar are electrically connected in series each to a conductor element providing connection to an external bus,
wherein said conductor element providing electrical connection of the collector bar to an external bus comprises a flexible connector strip which is made of copper or copper alloy.
2. The cathode current collector and connector assembly according to claim 1 , wherein the flexible connector strip is a flexible strip having at its ends connecting pieces of solid copper with rings or hooks for connection directly or indirectly to the terminal part of the collector bar and to an external bus.
3. The cathode current collector and connector assembly according to claim 1 , wherein said terminal part(s) of the collector bars comprise in the vicinity of said connector a zone of reduced cross-sectional area wherein the cross-sectional area of said zone of the terminal part is less than the cross-sectional area of the remainder of said terminal part(s).
4. The cathode current collector and connector assembly according to claim 3 , wherein the zone of reduced cross-sectional area comprises at least one opening, or recess or part of reduced thickness in the terminal end part of the collector bar.
5. The cathode current collector and connector assembly according to claim 1 , wherein said connector comprises a conductor block of the same copper or copper alloy as the collector bar, a different electrically conductive metal or a different copper alloy from the collector bar, and wherein the conductor block is attached to the terminal end part of the collector bar(s) such that it protrudes from above and below and/or laterally from either side of said terminal end part.
6. The cathode current collector and connector assembly according to claim 5 , wherein the collector bar comprises two spaced-apart arms joined at an external end by a cross-piece, wherein the conductor block is externally connected to the cross-piece, and wherein the two spaced-apart arms each comprise adjacent to the connection with the cross-piece, a said zone wherein the cross-sectional area of each arm is less than the cross-sectional area of the remainder of said arms.
7. The cathode current collector and connector assembly according to claim 5 , wherein the conductor block is connected to the flexible connector strip which is made of a plurality of strips or braids or embossed sections of highly conductive metal and wherein the conductor block is made of aluminium, copper or alloys thereof.
8. The cathode current collector and connector assembly according to claim 5 , comprising a bimetallic plate between facing surfaces of the conductor block and the collector bar.
9. The cathode current collector and connector assembly according to claim 1 , wherein said terminal part(s) of the collector bars comprise an outer protective casing of metal extending up to the vicinity of said connector.
10. The cathode current collector and connector assembly according to claim 9 , wherein the space between the collector bar and the protective casing is optionally filled with a compressible material of low electrical conductivity and low thermal conductivity.
11. The cathode current collector and connector assembly according to claim 1 , wherein at least one cathode is composed of carbon and/or graphite in a proportion of at least 50% by weight of carbon.
12. The cathode current collector and connector assembly according to claim 1 , wherein an upper part of the cathode contains at least one refractory hard metal compound like TiB2 and a lower part of the cathode is made of carbon.
13. A Hall-Heroult cell for the production of aluminium fitted with a cathode current collector and connector assembly according to claim 1 .