Simultaneous determination of nucleation and crystal growth kinetics of gypsum
Résumé
The chemical treatment of industrial effluent, containing sulphuric acid, is typically completed by neutralizing it with lime through solid/liquid separation. The mineral precipitation processes developed by Veolia Environnement use sludge recirculation. The production of a high sludge density characterizes these processes, at a minimum of at least 25% weight in solids. The first laboratory tests studied the precipitation reaction, confirming the production of gypsum (CaSO4 • 2H2O). Then the precipitation mechanisms, nucleation and crystal growth kinetics, are determined in order to establish a model which predicts population density in reactor in accordance with fluid dynamics. The determined nucleation and growth kinetics are then used to feed a reaction model, coupling computational fluid dynamics (CFD) and population balance modelling to simulate the precipitation process.