BUBBLE TRANSPORT BY ELECTRO-MAGNETOPHORETIC FORCES AT ANODE BOTTOMrnOF ALUMINIUM CELLS

摘要

Electrically conducting and nonconducting particles and bubblesrnexperience additional forcing in a liquid which carries electricrncurrent. These so called electro-magnetophoretic forces are wellrnknown in metallurgical applications, like metal purification inrnvacuum-arc remelting, electro-slag processes, impurity removal orrnconcentration change in special castings. However, the effect ofrnelectro-magnetophoretic forces has never been considered forrnaluminium cells where the gas bubbles evolving in the liquidrnelectrolyte are surrounded by an electric current and significantrnmagnetic fields. We present models to estimate the effect of electricrncurrent flow in the vicinity of the bubbles and the additionalrnpressure distribution resulting from the magnetic forces in thernsurrounding liquid electrolyte. According to the estimates, thisrnforce becomes important for bubbles exceeding 2 mm in size, andrncould be sufficient to overcome the typical drag force associatedrnwith electrolyte flow thereby opposing motion of the bubble alongrnthe base of the anode when it is inclined at a slight angle. The effectrncould explain certain features of the anode effect onset.rnMathematical models and numerical results are presented and arnfurther implementation in the general MHD code for the aluminiumrncell design is discussed.