Reactions of lime under high temperature Bayer digestion conditions

This paper collates existing information from the literature on the reactions of lime added directly to high temperature Bayer digestions. It examines the reaction of calcium in lime with liquor components to form reaction products. Reactions are considered individually and in competition with each other. Because of the scarcity of information about competing reactions involving calcium/lime, the paper contains some speculation, drawing on different pieces of evidence from the literature to suggest possible reaction pathways. Three lime types have been considered - slaked lime (Ca(OH)(2)), calcite (CaCO3) and tri-calcium aluminate (TCA, Ca3Al2(OH)(12)). Individual reactions of calcium in lime have been considered with alumina and carbonate, fluorine, vanadium, phosphorus, silica, titanium and iron. Consideration has also been given to the catalytic actions of lime in transforming goethite to hematite and enhancing boehmite dissolution. Crown Copyright (C) 2015 Published by Elsevier B.V. All rights reserved.