IMPROVING THE FILTRATION OF ALUMINA TRIHYDRATE AT EURALLUMIN A

摘要

Prior to calcination, alumina trihydrate must be washed and dewatered to reduce the energy required for removing residual moisture during calcination and to produce alumina having the lowest possible teachable soda. At Eurallumina this is accomplished using Dorr-Oliver multi-stage table vacuum filters operating in the countercurrent mode.During the past few years a chemical drainage aid, Nalco N7846 POWER-DRY , has been extensively evaluated on the hydrate filters. The addition of low levels of this product into the wash water circuit resulted in significant reductions in cake moisture and soda. In addition, beneficial improvements in other operating parameters, such as better control of filter vacuum, were also observed. Details for the optimal application of the drainage aid and the resulting improvements in product quality and filter operability are presented.