TRACE ELEMENT CONCENTRATION IN PARTICULATES FROM POT EXHAUST AND DEPOSITIONS IN FUME TREATMENT FACILITIES

摘要

In dry cleaning of pot exhaust, expensive uorides are captured and returned to production. At the same time impurities are accumulated in the _ner fractions of the secondary alumina fed to the cells. While in secondary alumina the impurity content increased in the _ner fractions, raw gas revealed a signi_cant increase in impurities for particles with Di > 1 _m.Fume particles were sampled using a cyclone with varying cut-sizes and analyzed with help of HD ICPMS.A statistical approach is used to identify correlations between element concentrations and particle diameters. Maximum impurity concentrations were recorded for fume fractions with particle size Di > 10 _m. It is expected that an economically feasible way of removing coarse particles from pot exhaust will lead to improved metal quality and increased current e_ciency while keeping uoride losses at a minimum.