Bayer refinery alumina recovery is a strong function of extraction in digestion and alumina losses throughout the plant. One of the most significant of these alumina losses is the auto-precipitation, or reversion, of alumina in the clarification section of the plant. Settler and washer alumina reversion has been the focus of an ongoing research and development project at QAL.
Work done at the QAL refinery to minimise alumina reversion in clarification includes:
- Studies into the reaction kinetics of reversion
- Development of a plant model incorporating the reaction kinetics, and the validation and tuning of this plant model against plant data
- Use of the plant model to evaluate options to reduce reversion
- Plant trials
- Implementation of improvements into plant operation
This work has led to significant improvements in plant performance, including a reduction in lead washer reversion by approximately 80%.