CHEMICAL ADDITIVES FOR THE BAYER PROCESS - BUYER BEWARE

Graham, G.A. and Davies, T.J.

The impact of an ever-increasing range of potential chemical additives to the Bayer process is examined, with respect to their effect on hydrate crystal agglomeration and growth. Ultimately, these compounds may influence alumina particle size distribution or other quality parameters.

It is known that some combinations of chemical compounds enhance hydrate particle size and are marketed as "crystal growth modifiers". A number of other chemicals, for example those which form part of the defoam, flocculant and drainage aid groups, can have significant negative effects on particle size in precipitation,

The "down side" of suppliers not disclosing their formulations is that compounds which adversely affect the process may be unwittingly introduced. Communication between the user and the supplier of chemical additives needs to be improved to the mutual benefit of both.