Everett C. Phillips

Opportunities for Improved Environmental Control in the Alumina Industry

Alumina production from bauxite offers a unique set of environmental concerns that affect air, water, and solids. Governments and industry have recognized that reductions in plant emissions and environmental impacts are necessary. The alumina industry is not the only industry that has been subjected to, and responded to, such regulatory scrutiny over the past decade. A number of industry sectors are actively developing innovative ways to control a broad range of potential environmental hazards. Several of these technologies may have direct application in alumina refineries. Methods to significantly reduce mercury emissions in both air and water have recently been developed for use in a range of industries. This paper reviews some of these new technologies now in commercial use in non-alumina plants and considers how they may be applicable within the alumina industry.

Effects of Temperature and Method of Solution Preparation on the Performance of a Typical Red Mud Flocculent

Alcan International Ltd. in collaboration with Ondeo Nalco Company have carried out a fundamental study on the dissolution and performance of a 100% anionic polymer. The effects of method of preparation, solvent composition, temperature and exposure time on flocculent activity under conditions relevant to both atmospheric and pressure decantation were investigated. Flocculent activity was determined using static and dynamic settling tests, and the results were correlated with the reduced specific viscosity (RSV). For any given method of preparation of the flocculent solutions (makeup/dilution) the RSV tended to decrease with increasing solution ionic strength, independent of ionic speciation. While a significant loss in flocculent activity occurred with long exposure of the solution to high temperature, only a minor loss occurred in the short time required to flocculate and settle the mud in a decanter operating at 150 °C. Recent results in an actual plant pressure decanter appear to validate this conclusion.