PHYSICAL MODELING STUDIES OF ELECTROLYTE FLOW DUE TO GAS EVOLUTION AND SOME ASPECTS OF BUBBLE BEHAVIOR IN ADVANCED HALL CELLS .2. FLOW AND INTERPOLAR RESISTANCE IN CELLS WITH A GROOVED ANODE

This article illustrates the role of anode design in increasing the en ergy efficiency of advanced Hall-Heroult cells. In this study, a ''nov el'' anode that promotes the removal of gas bubbles, generated by the anodic reaction, from the interelectrode gap has been simulated. The e fficacy of this anode has been judged with the help of electrolyte flo w and interpolar resistance measurements in the horizontal, near-horiz ontal, and near-vertical electrode configurations. The experimental ar rangement was similar to that used in Part I, the companion article. V elocities were measured with a laser-Doppler velocimeter (LDV). Both v elocity and interpolar resistance measurements indicate the superiorit y of this novel anode over a flat anode. Use of this novel anode (vis- a-vis the flat anode) should lead to a reduction (approximately 40 pct ) in interpolar resistance at current density levels used in the indus try. Furthermore, electrolyte flow in the anode-to-cathode gap (ACG) i s uniform, thereby minimizing the possible problem of reoxidation of a luminum which might be present in cells operated with flat anodes. Thi s study also highlights the major drawbacks of advanced Hall cells ope rated in the near-vertical configuration: existence of recirculating f low and very high volume fraction of bubbles near the top of the ACG. Both of these factors could lead to increased oxidation of aluminum an d, therefore, to reduced current efficiency. Finally, comparison of re sults with Part I suggests that maximum energy efficiency should be ob tained in retrofitted advanced Hall cells operated with this novel ano de in the near-horizontal electrode configuration.