Bubble transport by electro-magnetophoretic forces at anode bottom of aluminium cells

Bojarevics, Valdis and Roy, Alan (2011) Bubble transport by electro-magnetophoretic forces at anode bottom of aluminium cells. In: Light Metals 2011. John Wiley & Sons, Inc., Hoboken, NJ, USA, pp. 549-554. ISBN 9781118029350 (print), 9781118061992 (eISBN)

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Abstract

Electrically conducting and nonconducting particles and bubbles experience additional forcing in a liquid which carries electric current. These so called electro-magnetophoretic forces are well known in metallurgical applications, like metal purification in vacuum-arc remelting, electro-slag processes, impurity removal or
concentration change in special castings. However, the effect of electro-magnetophoretic forces has never been considered for aluminium cells where the gas bubbles evolving in the liquid electrolyte are surrounded by an electric current and significant magnetic fields. We present models to estimate the effect of electric current flow in the vicinity of the bubbles and the additional
pressure distribution resulting from the magnetic forces in the surrounding liquid electrolyte. According to the estimates, this force becomes important for bubbles exceeding 2 mm in size, and could be sufficient to overcome the typical drag force associated with electrolyte flow thereby opposing motion of the bubble along the base of the anode when it is inclined at a slight angle. The effect
could explain certain features of the anode effect onset.
Mathematical models and numerical results are presented and a further implementation in the general MHD code for the aluminium cell design is discussed.

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