THE CONTROL OF FLUORIDE CONCENTRATION IN ET? ALüMINYUM BAYER REFINERY LIQUOR

摘要

In the ETI Alüminyum Bayer Process liquors, fluoride is evidentas an undesirable impurity, because it presents itself as aprecipitate of Sodium Fluoride (NaF) in the higher concentrationliquors, which has two mal effects, one of which limits the causticconcentration that ETI can attain, and the other is its solid phasepresents as scale.Spent liquor from precipitation is fed to evaporators. To improvealumina extraction in autoclave liquor it was decided that thestrong liquor caustic concentration be gradually increased. It wasnoticed that scale formation in the strong liquor pumps andpipelines dramatically increased. XRF and XRD characterized thescale as ‘Villiaumite’ (NaF). Research on Villiaumite found that itstarted to precipitate at higher caustic concentrations. Thesolubility of NaF was evaluated and saturation levels weredetermined. As a result of this study control of NaF precipitationis practiced by ET?.