A NOVEL DESIGN CRITERION FOR ALUMINA FEEDERS IN ALUMINIUM ELECTROLYSIS CELLS

摘要

The theoretical possibility of agglomeration-free alumina feedingin aluminium reduction cells is addressed. The treatment is basedon calculated times for dissolution of alumina particles and theirterminal velocity in the bath. It was found that the dissolution ratefrom a few hundred grams of alumina kept in dispersion issufficient to supply the entire cell. To derive a criterion fordispersion as single particles and avoiding agglomeration, twotypes of consideration were made; 1) The volume fraction of solidalumina sinking through the bath at a rate corresponding to theconsumption must be considerably below unity, or 2) Particleslanding on the bath surface must have time to sink away beforethey are hit by succeeding particles. The two considerations endup with very similar mathematical expressions. Based on thederived criteria, normal point feeding produces agglomerates,while continuous feeding to the same surface area may producesingle particles.