The nature and impacts of fines in smelter-grade alumina

Fines in smelter-grade aluminas art recognized (is a significant process problem in aluminum smelting. However understanding the nature of this fine material and how it impacts the reduction process arc, less clearly understood The combination of new analytical methods such as variable pressure scanning electron microscopy and very; high field solid state nuclear magnetic resonance provide new insights into the phases present and their spatial distribution within aluminas, and suggest how such fine materials are generated, particularly during calcination in the alumina refinery

Characterization of metallurgical-grade aluminas and their precursors by 27Al NMR and XRD

The structure of metallurgical- or smelter-grade aluminas (MGAs) is complex and poorly understood. Ultra-high-field solid-state 27Al NMR results on industrial as well as on laboratory-prepared aluminas are discussed in relation to XRD results. It is demonstrated that high-field NMR can effectively be used to quantify the proportion of the thermodynamically stable alpha-alumina phase in these materials. The results demonstrate that 27Al NMR is a vital adjunct to XRD methods to quantify the transition alumina phases that invariably dominate the MGAs. The nature of the disorder in these materials, determined by 27Al NMR, is also compared with literature data, such as XANES and EXAFS studies, on typical laboratory-prepared materials. The utility of 27Al NMR studies to provide new insight into the structural complexity of metallurgical aluminas is shown. © 2007 NRC Canada