CAN GIBBSITE PRECIPITATION BE MODELLED FROM FIRST PRINCIPLES ?

llievski, D.

The paper explores the possibility of developing a complete gibbsite precipitator model based on fundamental principles of physics and chemistry. Some of the recent developments in precipitation research are described. A review is given of the types of mathematical models currently used to describe precipitator behaviour (eg. the population balance) and the models used to describe the mechanisms of precipitation kinetics. The reviews are based only on information available in the open literature.

The mathematical formulation of precipitator models to describe the yield and crystal size distribution behaviour can be based on rigorous mathematical and physico-chemical principles. However, the expressions used to describe the individual kinetic mechanisms (growth, nucleation, agglomeration, breakage and attrition) are currently represented by empirical correlations. This is because understanding of these kinetic mechanisms is poor. In fact, often these empirical correlations are unsatisfactory; for certain kinetic processes it is not even clear which of the process variables should be included in the correlation. Thus, it is currently not possible to develop fully a precipitator model from first principles.