Reduction cell for producing aluminum

A cell for producing aluminum by the electrolytic reduction of aluminum chloride, comprising:

• a plurality of electrode stacks arranged in pairs, wherein each electrode stack comprises:
• an upper terminal anode;
• a lower terminal cathode;
• and
• one or more intermediate bipolar electrodes disposed between the upper terminal anode and the lower terminal cathode in a superimposed, vertically spaced relationship defining inter-electrode spaces, wherein the upper surface of at least one of the intermediate bipolar electrode comprises hydro-dynamic slots of varying dimensions;
• a plurality of bath supply passages extending downwardly along one side of each electrode stack, and in fluid communication with:
• (a) a bath reservoir located above the plurality of upper terminal anodes;
• (b) each inter-electrode space for that stack;
• and (c) an aluminum product sump located below the plurality of lower terminal cathodes;
• and
• a plurality of bath return passages extending upwardly between each of the paired electrode stacks, and in fluid communication with:
• (a) each inter-electrode space for both of the paired electrode stacks;
• (b) the bath reservoir;
• and (c) the aluminum product sump.